DE2031773A1 - Protective coating on metal substrates through electrolytic deposition of chromium components - Google Patents

Description

Protective coating on metal substrates by electrolytic Separation of chrome components

For a long time, it has been the task of metal manufacturers to obtain a coating technique that would improve the corrosion and abrasion resistance, as well as the paint adhesion properties, of ferrous metal objects, e.g. B. pipes, bolts or screws, nuts, sheet steel and the like, which have previously been treated in some cases with corrosion-resistant zinc and cadmium metals, in other cases with other corrosion-resistant compositions or in other cases with no corrosion-resistant materials, are significantly improved. In order to deliver a successful coating process, the method used must not only reduce the oxidative contamination of the metal substrate and improve its abrasion and impact resistance, but also provide a suitable base for paints and coats of paint and good welding properties.

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be added. While so far by the electrolytic Chromium plating has had some success, and so is chromium oxide plating subject to attack by alkaline solutions. In many applications, there are also problems with the low abrasion resistance.

The invention is based on the discovery that one of the most promising methods of protection is that of electrodeposition of a thin duplex chrome coating (mixed Material made of metal and chromium-containing compound) on the surface of the metal substrate to be protected. Especially in the test, the corrosion and abrasion resistance as well as the paint adhesion properties of steel, black iron and coated with zinc and cadmium To improve steel and to bring about good welding properties, a lot of research was done for the development

Development of an optimal method for the deposition of a duplex chrome coating on the surface of the metal substrate to be protected expended. As an example of the sensitivity of the chrome plating process working conditions it has been found, for example, that the regulation of the activator (catalyst) addition both the deposition of the Chromium metal as well as the chromium-containing compound. It was also found that the deposition of this Components critically depend on the pH of the Bath and the treatment current density depends.

Particularly inexpensive duplex chrome coatings from the standpoint of Impact resistance, bonding, abrasion and corrosion resistance, weldability and paint retention were according to of the invention obtained in that a double coating is deposited electrolytically, which consists of a combination

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nation is made up of chromium metal and chromium-containing compounds that are insoluble and soluble in a caustic solution (it is assumed that these compounds are chromium oxides in the trivalent and marine state), the chromium metal providing the necessary hardness to protect the coating against abrasion. However, the deposition of an effective amount of chromium metal during an electroplating process is directly related, among other things, to the acid content and electroplating current of the solution. ■ traversing ens i an insignificant amount of chromium metal during the course of elek'trolytischen coating on the substrate - even, if allowed to rise 0 the pH of the solution · on the value of about 2 *, separates out '■'. As a result, the coatings produced show insufficient resistance to abrasion and impact. Likewise, if the electroplating current is not maintained at an adequate level, ie, at least about 6 amps per square foot of cathode metal surface, the amount of chromium metal deposited in the coating will drop sharply away.

Previous efforts in applying chromium coatings to zinc-coated metals are discussed in US Pat. No. 1,853,323, which teaches immersing a zinc-coated article in a solution of 250 grams of CrO 1, 3 grams of Cr ₂ (SO ^) ₅ and 1000 cm ^ H ₃ O for about 3 minutes at a current density of 1 A (60 Hz alternating current) - per 6.5 cm (square inch) and at an electrolytic bath temperature of about 80 ° G a colored coating on the zinc-coated object results. This patent teaches the use of an alternating current (AC current); in contrast, the present invention employs direct current (DO) electrodeposition.

009886/197

2,31773

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Recently published U.S. Patent 3,296,100 and Process for Coating Tin-Free Steel with Layers of Metallic Chromium and. Chromium Oxide ", J. Electrochem. Soc: Electrochemical Technology, March 1969, pages 398 to 402 provide the further background for understanding the inventive Improvement in the field of electrodeposition of chromium on metal objects. In the above cited references is a method for the electrodeposition of a two-layer coating from metallic chromium-non-metallic chromium oxide on one immersed in a bath of chromic anhydride and chromium sulfate Steel plate described. The double layer coating has a base of metallic chrome and a layer on top associated layer of non-metallic chromium oxide. The procedure of the above references is limited, so that a "coating of two distinct Layers is produced, while, in contrast, according to the invention, a mixed coating of chromium metal-chromium compound will be produced.

The invention provides a new and improved method of coating steel or other metals with chromium to improve corrosion and abrasion resistance and the ability to apply paints while having good weldability is delivered. The new process enables the use of large quantities of hexavalent chromium compounds within a simplified, one-step electrolytic process for the deposition of chromium.

The invention relates to an improved method of applying chromium to a metal substrate using a wide working range of current density to achieve

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a duplex chrome plating of {any ratio of components made of chromium metal and compounds containing chromium contains, and relates in particular to a uniform duplex coating made of a mixture of chromium metal and chromium-containing Compounds (oxides) as a completely new subject. This coating composition, when applied to a metal substrate, provides a new coated article with highly desirable anti-corrosive and abrasion-resistant properties as well as extremely useful paint adhesive

and weldability.

The invention thus relates to the protective treatment of metal surfaces and particularly the "cathodic coating of Metal surfaces, e.g. B. iron, steel, zinc or other base metals. The "metal surface" mentioned here is the surface on which the duplex coating of the present invention is deposited. This surface can thus, for. B. a zinc-coated plastic substrate and, for example, zinc-coated steel or e.g. B. Steel itself. show without any Zwisphen coating. The procedure the invention relates generally to electrodeposition of a unique duplex metallic coating Chromium-chromium oxides from a hexavalent chromium and a chromium activator, e.g. B. emits a sulfate radical Material containing solution on metal. The preferred sulfating agent is sulfuric acid, which in terms of the simultaneous deposition of metallic chromium and chromium oxides on the metal substrate has a demanding effect, although others Activators are effective. In particular, the chloride anion and the pluorborate anion proved to be suitable chromium activators.

Due to the implementation of the inventive method

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The product produced here is called a "duplex" coating Chromium components, referred to. This term denotes a new two-component coating which is composed in a weight ratio of about 4 ·: 1 to about 1:30 with one another mixed metallic chromium and chromium oxides is built up. The distribution of this duplex coating is such that approximately 0.5 to about 65 mg of coating per 0.09 m (square foot) of metal surface Cover evenly. The metal base coated in this way is characterized by a significant improvement their properties in terms of resistance to corrosion, through improved impact and abrasion resistance and a significant increase in their ability to paint and paint applied to their surface

the end.

To retain paints ^ For steels coated in this way, it was found that that the coated steel can be welded easily, and there was no deterioration of the welding electrodes found in the case of resistance welding. In the case of steel, first with zinc and then with the one according to the invention Duplex chrome plating has been found that the coating inhibits the formation of an alloy between the zinc and the welding electrodes, thereby reducing the service life of the Electrodes was increased significantly.

The duplex coating of the invention was applied directly to otherwise untreated steel as well as to zinc or tin plated ferrous metal bases. Since it is consistent practice, coatings of non-ferrous metal which are applied to a ferrous metal base, by applying a chromium coating arranged over it protect, the product according to the invention acts as an improved chrome coating applied over it. With each application the duplex chrome coating according to the invention showed a considerable improvement in the overall quality properties of the basic

009886/1976

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metal or the metals to which the coating is applied had been. In particular, the corrosion resistance and paint adhesion strength of these metals have become remarkable improved.

The properties of corrosion resistance and paint adhesion of ferrous and non-ferrous Substrates can by applying a composite coating of zinc-containing material, preferably electrical ■. Plated or hot-dipped zinc, followed by food coating made of tin or tin alloys (Sn-Zn, Sn-Ni, FeSn) again with a subsequent chromium-containing coating, z. B. Chromium and / or one or more chromium oxides can be improved .. It was found that the combination of Tin and duplex chrome, as well as zinc and tin and duplex chrome a significant improvement, especially in durability to hot rust corrosion of steel plates.

The method of the invention provides a new and essential one improved method for the deposition of such a coating mass on a metal base, whereby a rapid, Direct and effective one-step electrolytic coating technique is used / Basically this process is used an electrolytic plating bath was first prepared containing hexavalent chromium ions, e.g. Bv- from chromic anhydride or sodium dichromate, and a chromium activator, which supplies sulfate, chloride or fluoroborate ions. The activator can for example be selected from sulfuric acid, hydrochloric acid or fluoroboric acid. The pH of the bath is kept below about 2.0. A direct current that is generally in the range upward of about 6 A / 0.09 m (square foot) of the treated metal surface is passed through the bathroom. When the metal substrate is immersed in the bath as a cathode, it separates

• -

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on the substrate cathode surface quickly the invention measure duplex coating, which is a relatively thin layer an admixed mixture of insoluble and soluble chromium components in a caustic solution (sodium hydroxide), d. H. Chromium metal and chromium oxides.

It has been found that the ratio of the etchant insoluble and soluble chromium components in the obtained coating with the concentrations of hexavalent chromium ions and chromium activator ions in the coating solution ,, the current density applied during the coating process, the temperature and pH of the coating solution and the Speed of movement of the substrate in the coating

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solution varies. In particular, it was found that, even although the total Coulomb treatment per unit area of the substrate has been made constant by increasing the speed of the substrate within the solution (e.g. by changing the speed of a strip passed through the solution or by changing it, the speed of rotation of a sample rotating in the solution), the ratio of alkali-soluble components in which the coating is increased.

It was also found that when the concentration of either hexavalent chromium ions or chromium activator f ions within the solution increases, even though the ratio of hexavalent chromium ions to the activator ions remains constant, the ratio of alkali-soluble constituents in the coating increases. It was determined, that such an increase in the ratio of alkali-soluble ingredients in the coating is also reflected as a result a decrease in current density, a decrease in (temperature of the coating solution, a decrease in pH of the solution and a decrease in the ratio of hexavalent chromium ions to ghromat activator ions in the Coating solution adjusts.

■. '■ I

The invention thus provides a vastly improved method for both faster and increased deposition of both pure chromium metal as well as chromium oxide components of a chromium coating, which leads to a substantial increase in the Corrosion resistance of the treated metal as well as more effective operation of the cathodic treatment leads.

As indicated above, the proportions of alkali-insoluble and soluble chromium components in the coating by changing such process factors as

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for example substrate movement in the bath, concentration of the Bath components - bath temperature and pH value and current density, can be varied. The thickness of the coating on the substrate also depends on these factors as well as the total Coulomb value of the electroplating current per unit area of the substrate. The color of the coating is of these depending on the same factors, especially when they the ratio of alkali solubles contained in the solution Affect chromium components. It was found that, if the alkali-soluble components of the coating (chromium oxides) increase in relation to the insoluble components, the color of the coating becomes darker - This color change has been found to be in an electroplating process can be easily regulated.

As a result of the above-mentioned method of metal treatment, it was found that a uniformly distributed intimately mixed "duplex" coating is produced, the about 4 to about 80 wt.% In caustic solution insoluble chromium components contains, d. H. it is believed to be composed mainly of chromium metal and a small amount of insoluble oxides. About 96 to about 20 weight percent of the coating consists of chromium components which are soluble in caustic solution, i.e. i.e., it is believed that they are mainly consist of chromium oxides. This duplex coating becomes rapid deposited and has such a coating distribution that about 0.5 to about 65 mg of coating per 0.09 ^ (square foot) Cover the treated substrate evenly. The proportions of the alkali-soluble and -insoluble components in The plating can be varied to meet different quality standards to yield, e.g. B. the ability to apply the coating, weldability, corrosion and abrasion resistance.

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The present working method is ideally suited for the large-scale, electrolytic, cathodic treatment of metal bases. It is possible 'a large amount a metal substrate, e.g. B. pipes or sheet steel, to be coated rapidly within a few seconds, with an effective amount of a coating of chromium metal-chromium oxide deposited with virtually no depletion of the chromium plating bath will. .

The duplex chrome plating obtained as a result of the improved working method resulted in an improvement in durability of zinc-coated steel plates that have been subjected to the corrosive effects of brine or lye were from 100 to 250 hours. The adhesion of paints the surfaces of steel and iron treated in this way have also been significantly improved. The procedure can also be used in an equivalent manner to increase the corrosion resistance of other metal objects, e.g. B. from aluminum, magnesium or cadmium either as base metals or as metal coatings on a ferrous metal base or alloy can be applied. When zinc coated steel is treated, particularly good results have been obtained, when the zinc metal is present as a coating of 0.5 to 50 η (0.02 to 2.0 mils) thick.

In the drawings give

Fig. 1 is a sectional view of a treatment device.

according to the invention,

Pig. 2 shows a sectional view of the treatment device according to FIG

Fig. 1 along the section line 2-2 of Fig. 1,

3 shows a sectional view on an enlarged scale

treatment device shown in Fig. 2 along the section line 3-3 of Fig. 2,

Fig. 4- is a perspective view of an in the treatment

- - io -00.9.886 / 1974.

JFS 7522

Device of Figs. 1 to 3 used anode and

Fig. 5 "to 12 curves useful for understanding the invention

explain appropriate experimental data, again.

Before giving specific examples of the invention, the test method by which the coatings produced according to the invention are tested to determine the proportions of chromium metal and chromium oxide material to be determined. Each coating was analyzed to determine the proportions to determine the soluble and insoluble constituents in caustic solution. When checking the coating the following reagents were used:

'' 30 % NaOH (400 g / l)

5 % NaOH (52.7 S / l) 1: 1 H ₂ SO ₄ (18 η) 0: In-AgNO ₅ (16.9 g / l)

0.25 g per 100 ml of diphenylcarbicide, dissolved in acetone

Ammonium persulfate (reagent grade)

All samples of the coatings tested had the same area. In the following discussion, the amounts of reagents used to test a sample with a surface area of approximately 19 »6 cm (0.0218. square feet). In short, the procedure involved determining the components soluble in sodium hydroxide, which are assumed to be hexavalent and trivalent chromium oxides, with methods of determination the respective amount were applied. The insoluble one Ingredient believed to be chrome metal and oxides, has been caused by electro-stripping of chrome plating over steel and by chemical stripping Chromium components determined over zinc coated steel.

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A. Components soluble in ITaOH (Cr ⁺⁶ and

(1) 20 ml of 30% NaOH is applied to the sample surface in a detachment or stripping cell, not shown applied and allowed to react for 5 minutes progress.

(2) The caustic solution is poured from (1) into a 250 ml ~ Beaker transferred, and the cell and sample surface is rinsed with distilled water »

(5) The solution from (2) is neutralized with 1: 1 HgSO ^ and 0.50 ml of excess H ₀ SO., Is added in order to bring the pH to 1.4 · to 1.8 · The normality of the Acid in the solution should be kept between 0.05 to 0.2On.

(4) The solution from (3) is poured into a 100 ml volumetric Flask transferred and diluted to the mark with distilled water. ..'- ..

AT) Sub-procedure for the determination of hexavalent, soluble constituent ö

(5) An as-needed (4x) aliquot (usually 50 ml) is pipetted and transferred to a 250 ml Beoher glass and stored for analysis of bound Cr ⁺ * and Or ⁺ . The pipette is rinsed into the volumetric flask with distilled water.

(6) 2 ml of diphenylcarbicide solution are added to the volumetric Put in flask, dilute to the mark with distilled water, and mix.

(7) A portion from the volumetric flask is transferred to a 1.3 cm (1/2 ") cuvette and the transmittance is read in a spectrophotometer at a wavelength of 535 wu -" using distilled water as a reference . the

\ -12- ^:

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Permeability is expressed in mg Cr ⁺ per unit area of the substrate, based on known standard sizes

convicted.

A (2) Sub-method for the determination of trivalent, soluble component (Cr ⁺ *)

_{(8) Add 5} ml of 0.1 "AgHO 5 and a ladle () O to the beaker containing the above aliquot (5)

fel (HH ^) ₂ S ₂ Oq added. It is diluted to about 100 ml with distilled water; and kept simmering for 15 minutes.

(9) It is cooled, the solution in a volumetric eye Transfer 100 ml flask and add 2 ml of diphenylcarbicide admitted. It is diluted to the mark with distilled water and mixed.

(1O) Part of the. volumetric !! Flask (9) is transferred to a 1.3 cm cuvette and the transmittance is read in a spectrophotometer at a wavelength of 535 m # using distilled water as a reference. The permeability gives mg Cr ⁺ - * and Cr ⁺ per surface area of the substrate. "

(ii) The drainage value obtained in (10) above is subtracted from the value obtained in (7) above. The net permeability; is converted into mg Cr ⁺ * per unit area of the substrate, based on known standard values.

B. Chromium components insoluble in caustic solution (size ⁰ )

B (i) Untery learn about the determination of insoluble constituents of chrome coatings applied directly over steel

(12) Regarding the product still in the wiping cell

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benscheibe 20 ml of 5% is ^e NaOH solution was added, and the coating is electrolytically detached by the sample outer use is made of a platinum cathode to an electrical anode, and an Abl6suEgjsstrom of the sample anode to the cathode geleitet- 3 Hinuten is replaced with a current of 5 A.

(i5) The detachable song from (12) is put into a 250 ml beaker transferred, and the cells and sample surface is rinsed several times with distilled water. When the platinum cathode has become dark, | it is immersed in 10 to 15 hlL hot, 5% H ^ SO ^ for several "minutes and then rinsed. This acidic solution is added to the stripping solution obtained above. .

(14) The solution from (13) is _{neutralized with 1: 1 H 2} SO ^ and an excess of 0.5 ml HoSO _{7 is} added so that the pH is between 1.4 and 1.8.

The acidity of the solution should be in the range of 0.05 to 2.0a.

(15) If necessary, an aliquot according to the following procedure is taken after transferring the solution of (14-) into a volumetric 100 ml flask where diluted to the mark.

Cr ° / 0.C9 m ² (Ft ² ) aliquots

O - 3.5 5.5 - 7.0

7-10.5 10.5-14.0

All ml 50 ml 25th ml 10

009386 / 197A

(Ί6) The appropriate aliquot is poured into a

250 ml beaker transferred. 5 ml O, 1n AgNO, and |

2 - I.

a spoon full (NH ^ oSpOg are added. It f

is kept boiling for 15 minutes. One cools, |

and transferred to a volumetric 100 ml- * f flask, add 2 ml of diphenylcarbicide and
diluted with distilled water up to the mark «

(17) The transmittance is measured in a spectrophoto-

meter at a wavelength of 535 ma below | Use of distilled water as a reference 'j worth determined. . )

(18) The permeability value of (17) is expressed in mg } of insoluble constituent per unit area of the | Substrate, based on known standard sizes, j

convicted. \

B (2) sub-procedure for determination; insoluble components j

of chrome coatings applied over zinc n f

(19) To the treated with caustic solution under the vorste- i Henden step (1) and under the pre-: flushed stationary stage (2) 15 ml of sample [1: 10 ^ Hoso added and allowed \ are the mixture until the violent development of hydrogen ceases. The solution is immediately transferred to a j 250 ml beaker and rinsed with distilled [water into the cup. _; !

(20) One proceeds according to steps (15), (16) and (17) ■, j according to sub-procedure B (1). \

(21) The permeability reading from (20) is given in _ \ mg of insoluble constituent per unit area \ substrate, based on known standard sizes; convicted. \

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7522 .-. -

The above test procedures are intended for specimens, either steel or zinc plated steel as it turns out that are not plated with chromate can be repeated to Obtain data on untreated samples, subtract from the numbers obtained as described above can be used to provide precise determinations of the components of the coating.

In the test method described herein and the following examples, the coatings as chromium oxide and chromium metal components as well as Cr ^Q, Cr ⁺ * and Cr ⁺ i -Bestand- parts described. The constituent designated with Cr ⁰ and "chromium metal" is the chromium constituent which is determined under method B. "Chromium oxide" denotes the constituents which are determined under method A; Cr ⁺ * denotes the component that is determined by sub-method A (2); Cr ⁺ denotes the component determined by sub-method A (1).

Example 1

Black plate and larger thickness steel plates 10 cm (4 inches) wide by 30 »5 cm (12 inches) long and 7.6 cm (3 inches) by 20.3 cm (8 inches) were cleaned in an alkaline cleaner electrically cleaned, rinsed, activated in a dilute acid pickling bath, rinsed and cathodically treated in various chromium baths containing 20 to 100 g / l chromic anhydride.The bath temperatures were 21 to 66 ° C (70 to 150 ° S ¹ ) and the pH Value was kept below a value of 1.5 In the following examples the chromic anhydride sulfate ion concentrations were varied in a ratio from 300 j 1 to 25 s 1; the treatment current density was varied between .30 and 600 A / 0.09 in

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0 0 98 86 / 19-74 originally inspected

JFS 7522 $ 4

(square foot) and the treatment extent from 100 to 1000

Coulombs / 0.09 m (square / foot) varies.

The duplex chrome coatings produced weighed 4, 0 to 25 t.O mg / 0.09 m (square foot) and contained a ratio of Chrome metal to oxide ranging from 4: 1 to 1 ϊ 5 · This Chrome coatings have been (a) considered to be used for Can material using the sulphide pickle, synthetic beverage corrosion and the experiments described below regarding the release adhesion quality and (b) as a basis for paints and paints by salt spray tests. and moisture test rated.

I (A) C »Q ^ S. Quality check: en . ■

The abbreviation C, QJ.S. refers to chemically treated steel. Blackplate materials with a weight range ranging from 1.22 to 2 »2 kg / m ² (0.25 to 0.45 lbs per sq. Ft.) Were tested in test panels (1.8 5.4 cm (4 χ 12 ") and 1.4 x 3.6 cm (J χ 8") divided and covered with a duplex chrome coating under the following conditions: ·

(1) A treatment bath containing 20 g / l of chromic anhydride and 0.4 g / l of sulfate or sulfuric acid was prepared to give a hexavalent chromium ion to sulfate ion (Cr / SQ ₁ ^) ratio of 26: 1. The bath pH was about 0.7 and the bath temperature was about 26 ° C (78 ° F). The blackplate samples were cathodically treated at 50, 100,200, 500 and 400 amps per sq. Ft. Current density. The treatment values at each current density were JOO and 600 coulombs. / 0.09 m (coulombs per sq. Ft). The coatings obtained

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consisted of both chromium metal and chromium oxides. The coatings weighed 6 to 21 mg / 0.09 m (mg per sq. ft.). The metal to oxide ratios of these coatings ranged from 3 · 1 to 1 ί 4 ·.

The coated samples were painted, cured, into test coupons and container lids (jar caps) processed for qualitative testing - all manufactured duplex-coated Samples passed the sulfide stain, synthetic beverage and peel adhesion tests described below.

The peel strength of most samples was about 65 % higher i

than required for the morning standard.

(2) Similar Biiplex chrome coatings were used of the above electrolytic bath of (1) with the following Valvations with regard to the operating conditions manufactured:

(a) The salfate concentration is changed in such a way that concentration ratios of chromic anhydride to sulfate ions (GrCU / SOj.) of 25: 1 and 200 ι 1 corresponding to Gr / SO ^ ratios of 13: 1 and 104-: i were produced ^
Cb) the bath duration is increased to 66 ° 0 (150 ° P); '-

(c) the current limit is reduced to JO A / 0.09 m ² (amps per square foot;);

(d) the electrolytic treatment amount is given by

Reduction to 150 Coulomb / O 09 m or by

Increase to 1000 coulombs / 0.09 m ² varies. All of the coatings passed the quality control tests noted above. (5) In another. Good quality duplex chrome coatings have been produced from treatment baths containing 30, 40, 60, 80 and 100 g / l chromic anhydride under the various conditions specified in point (2) above.

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gen included. In this experiment, the chromic anhydride sulfate ion concentration increased to JOO: 1; as an alternative, the current density was set to 600 A / 0.09 m elevated. .

Paint test method and example therefor

from
A quantity / 6 ια (24 gage) of cold rolled steel material was divided into 10 χ 20 cm (4 χ 8 ") plates and treated in a bath containing 40 g / l of chromium. The sulfate concentration was between 0.30 and 0.80 g / The treatment current densities were 75> 100 and 225 A / 0.09 m · over a period of 2.4 ^ 2.0 and 1.0 seconds, respectively The duplex coatings produced weighed 7 to 4 mg / 0.09 m and contained a weight ratio of chromium metal to oxide in the range of 2: 1 to 1: 2.

Duplicate sets of uncoated control samples and duplex chrome-coated samples were treated with an organic solvent to remove any dirt from the surface. A coating of about 25 y (1 "O mil) thick of an alkyd melamine based paint known commercially as DuPont 707 was applied to a series of tests, and a urea formaldehyde based paint, known as Sherwin-Williams OTG was applied to the second series of experiments. After the panels had aged for 3 days, the panels were torn and placed in SaI ζ spray and moisture atmospheres for 500 hours. The experimental conditions for these special tests are described in more detail in Example 5 below.

The corrosion results for these test panels are in the

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Table I below. The bubble numbers (Mr. 4, No. 8) are ASSM ratings.

3? a b e 1 le I

Results the accelerated corrosion test 707 • - · Salζ spray test Corrosion Blistering Metal and experimental OTG crawl from $ AS3? M-D714) Treatment painted Scratches (in 1.6 µm, in Sixteenths of 707 Inch) OOJG 75 % painting (Painting ent Untreated, loss far away) cold rolled (500 hours) stole 75% painting (Painting ent loss far away) (3OO hours) 2 (500 hours)
2 C500 hours) Few Mr. 4- ElektrοIyti sch Satisfied with chrome be lend acted, cold rolled steel

moisture test

Metal and
treatment

Untreated, cold-rolled steel

Electrolytically with
Chromium treated,
cold rolled steel

% Loss when the surface of the plate is wrapped around

25 % loss

10 % loss

Blister formation (ASmB714)

Little No. 8 very k, lein

Means no. Very small

*. 20 -

1-974

GRlGfNALlHSPECTED

Ji ¹ S 7522nd ''"''

Example 2

Another set of iron samples of cold rolled steel was placed in the above bath as I (B) 1.0 seconds at 200 A / O, 09 m
(200 amps per square foot) treated cathodically. The duplex chrome coatings weighed 7.5 mg / 0.09 m (7.5 mg per square foot) and consisted of approximately 50 % chrome metal. The duplex chromium treated samples and those with zinc phosphate, iron phosphate? and chromate coating treated comparative samples
with Ί5] * · (0.5 mils) of a weldable zinc-rich green «=.
coating material (XP-104B from Yandotte Paint Products Company), baked at a temperature of 260 ° G (500 ° F for a minimum period of 30 seconds, and then dipped into a 5% strength for corrosion comparative tests)
Bred salt spray medium. The necessary stands to
1.0 and 10.0 % RotTGs.t of the base steel to ^: get ,. are shown in the following table II δ. , ".- ■■" .. ".

JFS 7522

Jab el 1 e II "

Confusion results with 5% core. Salt spray medium (materials coated with Wyandotte primer)

Coating or treatment over cold rolled stole

Coating test hours related

weight ο ^ er formation of red rust

ung / O, Q9 m on the steel base (mg / ft ² ;

Electrolyte solution 7> 5 Duplex chro-arabian style

Zinc phosphate

(commercially available Bonderite Kr-17 from the Parker 'Company}.

Eisenphospüai;

(HandelsprodsLtfc No. 901 from eier Parker

Company)

Microcrystalline chromate applied from a mass solution, squeezed out; baked in for 30 seconds at 232 ° 0 (4-50 ° F)

([Product of Mam Shamrock Goagpany)

Comparison - no treatment

1 % rust

10 % rust

312 216

144 96

432 336

240 168

72

These data show that the duplex chromium coating of the invention In comparison, corrosion of the base metal under the paint is delayed in a much more effective manner to other treatments or coatings that serve as a base used for painting.

In each of these top ratings, the generated Duplex-tlberaiig compared to the previous commercial products

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INSPECTED

JFS 7522 '

ζ. B. the cold-rolled one treated with zinc or iron phosphate Steel (Parker standard coatings 37 and 901 »in particular listed in Table II above) than superior. Thus, the duplex electrolytic chrome plating is found as an unusually effective coating material

Chemically treated steel (C.T.S.) Description of the quality tests

1. Peel-off adhesion test

This test was used to check chemically treated steel materials designed for metal container applications with glued overlapping seams are to be used for beverage containers. The test indicates the usefulness of the G.T.S. surfaces with regard to the peel strength of the .Putty adhesive. In short, the test consists of coating two samples of C.T.S. material with one specific varnish, then heat curing, cooling and cutting each sample into 19 mm (3/4 x inch) wide test strips. Adhesive pellets are then dot-attached to the ends of a painted surface. The other painted Surface is placed on top and the strips are heated at a specific temperature using a Plate press glued together. After cooling, the sample is placed in an Olsen tensile tester, over a holder of 180 ° is detached or removed, and the force required to remove the bonded seam is separated registered. A peel value below 11.3 kg / 19 mm (25 lbs. Per 3 / 4inch) is considered a failure and higher values are acceptable.

2. Corrosion test in synthetic beverages

This is an immersion test to determine corrosion resistance

0098867 ^ 74

Ji ¹ S 7522nd ^: . . . * V. *

to demonstrate under the egg of a lacquered and scored G.Ü? .S.-coating. A recommended, synthetic standard solution of 1.5% citric acid and 1.5 % sodium chloride is used as a corrosive medium instead of soda * or similar carbonated beverage solutions.In short, GTS samples are coated with a varnish, hardened and cut into strips of 1 , 1 χ 10 cm (7/16 χ 4.0 inch) cut. A cross is scratched on the burned-in surface with a glass cutter weighing 3.2 kg (7 lb). The samples are then applied to plastic strips using wax as an adhesive and to protect the exposed steel corners, then immersed in the distilled solution contained in containers. The test containers and the device formed above for evaluating the plate for beverages are used to provide the test atmosphere and to maintain a temperature of 27 ° G (80 ° J ") for a 4-day test period The width of the baked enamel raised by the tape along the heat mark is measured in mm with a calibrated eye glass A width greater than 0.5 mm is considered a failure and a width below this value is acceptable.

3 * SuIf id test .

The stain or discoloration test is used to evaluate the resistance of a lacquered G.3? «3rd coating opposite blue-black discoloration used when facing this one is exposed to a heated, sulfur-containing medium. This experiment is the usual pig packaging test similar (clad material is milled under heat ßchweineechu.lterfleisen exposed) for tinplate.

009886/1974 originally inspected

■ 7522 If ₁

is applied, but it is more stringent as a 0.5% sodium sulfide solution is used in place of pork. CTS samples are coated with varnish, then hardened, cooled and punched into container lids · ■ The lids are screwed onto 8 ox spherical containers, half of which are filled with the sulphide solution at 116 ° '-O. (240 ° F). After refrigeration, the containers are stored for 24 hours, then their lids are removed for inspection. Since this is an extreme test, only the lid centers and profile rings are evaluated with regard to discolouration. Furthermore, the paint adhesion is determined by scratching a cross on the paint surface tested for discoloration and performing the adhesive tape test. tarcL Preliminary attempts have no relationship »wipe. dea ^- ¥ discoloration and 'varnish-coating propertiesea eL © s CSS-Übers & gs result «,""" -

B is ν ie 1 ■ ■ "5 - - '

The following comparative evaluation of the invention. Duplex ear covers explain how they are used when they are used to protect a ferrous metal sample coated with zinc.

The test samples were used in the previous examples described way. The duplex covers weighed 8 to 14 mg / 0.09 m (milligrams persquare foot) and contained 17% by weight and above of metallic chromium component

ORIGINAL! NSPECTEO

009888/1974

JFS 7522

Cyclic Humidity Test (ASTM Bulletin 187 January 1935.)

Commercially available, electrolytically coated with zinc Strips with an average zinc thickness of 3.18 / U (125 microinches) was used as the sample material used in this rating. Rows of comparison and test plates were cleaned. A number was with the Duplex chrome plating and the other row with a bonderite or treated with phosphate coating. These and the comparative samples were then placed in the cyclic humidity test for comparison. The results that are refer to an average hourly value that is necessary to start to 1.0% red rust of the Panel edges to get are as follows:

Treatment of the test coating Medium hour steel sample number from the beginning

up to 1.0 % red rust on the edges ■

Electrolytic no 192

Zinc

Electrolytic phosphate, _o 184

Zinc 170 mg / O ^ *

(square foot)

Duplex electrolytic chrome _? $ 64 Zinc '.''. 11.0 mg / 0.09 m

(square foot).

B. 5 ^ ip; er salt spray test

The duplex chrome plating was electroplated over and hot-dipped zinc coatings and applied via vacuum zinc coatings for corrosion assessment in the salt spray medium. The corrosion results are listed below:

- 26 009886/1974.

JFS 7522

Evaluated material

Zinc starch on the base

[Salt spray exposure and hours until the onset of red rust FC

Controls

Duplex chrome

metal (steel) no coating coating

Additionally achieved service life in the salt medium
(Hours.)

Electro-galvanized zinc coating (zinc bond)

Hot dipped Zinc coating

Zinc coating applied by vacuum deposition

(0.180 mils)

22.9 / ι (0.900 mils)

(1.00 mils) (1.25 mils)

_ 4.5 170 120

420 180 -

480-590 120-230

675-695 240-260

From the above data it can be seen that the electrolyte table ear mat covers additional red rust protection from 100 to. 260 hours regardless of the thickness of the zinc coating self surrender.

Example 4

The following specific embodiments serve to further illustrate the usefulness and practice of the invention by describing a typical preparation of the duplex chromate coating and comparative evaluations of the coating against previously available commercial coatings particularly used as basecoats for further paint applications will.

- 27 -.

00-ÖBB6 / 1974

7522 IP

Α · Production of the! Plague Samples

Hit zinc plated materials for {plague plates

A leg of zinc plated materials was procured and placed in 7.6 to 20.3 cm (3 by 8 inch) plates. subdivided, which served as! embossers for test purposes. Pur ^ Every material was technically or im the weight of its Laboratory deposited zinc coating and weight its paint-adhesive or corrosion-resistant test coating determined before the assessment * These seeds are listed in OJabelle III, |

- 28 -

009886/1974 originally inspected

JFS 7522

Q? but _r 1 1 e III ^: '■ - ... .

Zinc-coated materials for anti-corrosion protection>"physical and corrosion versa © lie '- - _; - ,.

Ferrous base material

Zinc bond zinc bond

Zinc bond zinc bond

Source for the basic material

customary

plated

zinc

customary

plated

phosphated

commercial hot upsetting

He phosphates zinc bond

Glavanized plate

Galvanized plate

Galvanized commercially available hot-dip zinc average. "
^: ^ 4ehe zinc: ·
strength

"Über2üg '.:. <C» the "Be hahdXuns-about. * "the -Z & n & plate ■"

/ ^a (HicroiiicliLes)

-4.44- (175) ".- feeia-

(175)

- *, 44 (140)

21.3 (840)
21.3 (840)

21.3 (840)

- ear- 45 aäliümwand-

Boaderite;
(im:. Labp .- * - i ^:

2j5

.Äospnat-

commercially available 250. borrowed Bpn-

derit. ·. _ ' (IPtipsphat)

no "- ■ - _ä '—-

Bonderit 125 (in the laboratory
m. phosphate coated

electrolytic 12 table

c-ohrom

- 29'-

009886/1974 , II,

ORfGiNAL INSPECTED

JFS 7522.

Table III (continued)

Ferrous base material

Source for., The basic material

Average zinc strength in η (microincnes)

Plating or treatment over the zinc plate

Art

Galvanized commercial hot-dip zinc

Vaporized zinc plate

Vaporized zinc plate

Vaporized zinc plate

Laboratory vacuum chamber

15.9 (625)

26.1 (1035)
26.1 (1035)

26.1 (1035)

Zinc phosphate

phat over-

train

no

Zinc phosphate

(coated in the laboratory)

Chromate conversion coating applied by dipping

The commercially available phosphate coatings were applied in a continuous strip plating row by spray treatment. The phosphate coatings applied in the laboratory were dipped and brushed on . \ C _r

Excellent material 2 seconds was immersed in a laboratory chromating bath containing specific concentrations of hexavalent Chromium and an Aktivatoröubstanz contained.

Ultimately, the duplex chrome plating became the invention on the various zinc coated steel bases using the method generally discussed above.

I I

- 30 ■ - ■
009888/1974 ''

JES 7522 3 ^

brings. In the present case, these test panels in particular were immersed in an electrolytic chromic acid bath having a bath temperature of 27 ° 0 (80 ° F) and a ratio of chromic acid to sulfate ions of 50 'x 1, which causes simultaneous deposition of chromium metal and chromium oxide in a mixed precipitate . The electroplating current is controlled at 50 amps per square foot and the bath residence time is set at 4 seconds + 1 second. After drying, the samples are now ready for further treatment with paint and subsequent evaluation.

B. Applying a paint to the test panels

The test panels prepared in the preceding steps were washed with a common organic solvent treated to remove any grease or dirt from the surface and a thin coating of about 25yU (1 mil) thickness of an oil-based paint evenly applied to it. On a run of the test samples, one known commercially as the DuPont 707 became Painting based on alkyl ".- melamine and on a second series of experiments , a urea-formaldehyde-based paint known commercially as Sherwin-Williams OTG (hereinafter referred to as test paint A and B, respectively).

Those produced for testing in the weatherometer Samples were with modified alkyl designation paints provided by the Sherwin-Williams Company. All of the painted test panels were then at least 5 days before the start of the various test procedures to determine the value of the various corrosion resistant ones Primer coats on which the

0 0 9.8 8 6/1 9 7 A

JS ¹ S 7522 33

strokes were applied, aged. O. Testing and evaluation

The plague plates made of zinc-coated steel, treated in various ways, on which the corrosion-resistant material is applied _{; f} had been applied as indicated above (but not necessarily the same identical coating weights) were evaluated with regard to; their relative 'ability to withstand corrosive attack and also to maintain the integrity of a paint applied over the layer of anti-corrosive material. The test plates, which are marked with marking paints of 25 a. (1.0 mil) thickness were scored with a vertical scratch and tested for 20 days. The daily cycle of this experiment consisted of soaking in water for 5 hours and then treating in the weathering device for 17 hours * In this latter treatment, the samples were rotated, sprayed with water and dried with ultraviolet light every 2 hours. The results are summarized in Table VI below ί.

; I I ■. I '. ι ιΐ

III, It (I.

- 32 - ■ .- ■■ ··. "·. V ¹ -'-

'■■ Il, 1 ._, -. ■■

ORIGINAL INSPECTEÖ '

009886/1974

. ι ι ι

YY ¹ S 7522

T a bell e

Soaking weathering tests of marking paints over

treated zinc coatings

Substrate material treatment or surface treatment

Commercially available steel base with electrozinc (zinc bond)

Pure aluminum (comparison)

Commercially available steel coated with electrozinc

Commercially available zinc coated by hot dipping stole

Commercially available zinc coated by hot dipping stole

More commercially available by hot upsetting zinc plated steel

More commercially available

• η ii "

Duplex chrome

no

Commercially coated with phosphate

Coated with phosphate in the laboratory

Uärmebelierten for! Education of galvanic burn-in coating (Galvanneäl)

Amorphous zinc oxide with traces of iron and Cobalt

Commercial Iridite mi "h Ohrotnnt Review
1 (best)

2-; '.' ■■.

3 ■■ "■■■"; ■: ■; '■

Commercial no electrozinc

More commercially available. none by hot dipping zinc plated steel

9 (worst)

The ratings were based on the extent of paint peeling and blistering, the corrosion creep of the

- 33 -009886/1974 BAD

JPS 7522 3>.

Bite and soap build-up. Aluminum was also tested as a comparison.

The electrolytic duplex chrome coating according to the invention again showed superior performance in this test compared to the treatments listed above or Coatings.

The second series of tests, the results of which are given in Table V, comprise various specific test procedures, those used to measure the resistance of the painted coating to external exposure Force are trained. These attempts are as followsί

The Olsen Button Test - This test consists of placing the coated test plate with its painted side up in a holder so that it rests horizontally over a vertically arranged rod, on the top of which is a steel ball of 2, 5 cm (1 inch) in diameter. The upward movement of this rod is displayed on a sensitive indicator which is initially set to zero. The rod is slowly moved upward into the steel plate until the 2.5 cm (1 inch) diameter ball 7 * 6 mm (0.300 inches) has been pressed into the plate. The panel is inspected for cracking after every upward movement of 0.25 mm (0.010 inches).

The break point of the paint is recorded, and the paint adhesion is tested by applying ceilophan tape to the drawn area and then quickly again is replaced. The higher the value in cm, the better the integrity of the paint coating tested.

00988.6 / 1974

Ji ¹ S 7522 oC>

Attempt to determine the percentage of paint loss -

When using the Olsen Button test above, the percentage of the area directly above the Impact point, which is caused by the. Application of the cellophane tape loses its coating, registered. The lower the value in this test, the better the tested product is.

The Reverse Skiing Test (Gardner and Sward, Physical and Chemical Examination of Paints, Varnishes and Lacquers, 12th Edition, Gardner Labs, Bethesda, Maryland) - This test uses a 0.9 kg (two pound) weight that is resistant to a shock of 51 cm / 0.45 kg (twenty inches / pound) is equivalent. At its end it has a steel ball with a radius of 2.5 cm (one inch). This pendulum is dropped from varying heights onto the unpainted side of the test panel. The experimental readings are taken as cm / kg of palis. The test panel is examined to identify and record the lowest point at which icing occurs on the paint. The higher the value, the better the quality of the paint coating.

The V Notch Test - This test measures a percentage of paint loss obtained after wrapping the apex of a V-shaped notched piece of metal on a painted surface and then pulling the tape away from the painted surface.

The following data listed in the table shows the Comparative evaluation of the various corrosion-resistant coatings in the above-mentioned test methods. Of the inventive coating is either as with electrolytic Duplex chrome treated zinc bond (electroplated

- 35 -009886/1974

JPS 7522

zinc on steel), galvanized steel or with zinc vapor clad steel, etc., as appears in each series of tests listed. In any case, they result for the electrolytic coating in'dem Olsen Button test, reverse impact test and the V-notch test experimental values obtained a clear improvement compared to other evaluated samples and especially compared to the commercially available ones Standard phosphate coatings used as a base for paints be used.

009886/1974

Tabel Physical test results determined by series

Marry

Metal and
treatment

Test- Olsen Button on- for paint coat crack formation cm (inch)

Zinc bond
(electroplated zinc
on steel)

Painting specification
(Eaintlok;
comparison

Galvanized steel

Untreated \ A zinc bond B

Chrome-plated in the laboratory arium by B dipping Zinc bond

Electrolytic A with duplex chrome B treated zinc bond

Commercially available A phosphat over B zinc electroplating

Untreated

With electrolytic A duplex B Chrome treated

(0.220)

CO ₁ ;

o, 56

0.65 (O; 250)

0.61 (O _? 240) O.76 + (O.300 +)

0.66 (0.260) 0.76+ (0.300+)

(0.230) (0, "

270)

0.56
0.69

0.53 (0.210 } 0.63 (0.250)

0.53 (0.210V 0.76 (0.300)

% Paint loss after wrapping a 7 »6 mm (0.300 inch) button impression

,
100

The other way around
Impact test for paint cracking
cm / kg (inchpounds)

68
23
68
34

68

68
23

23
23

23 (20)
46 (40)

V-notch test % loss when wrapping around the vertex of the notch

100 100

100

90

90 50

100 100

50 100

10 10

row

Metal and
treatment

co
co
co

Table V. (Continuation)

Test- Olsen Button% paint- reverse to- for paint loss after impact crack formation wrapping such as

of a 7.6 mm line crack

(0.300 inch) education

Button on

pressure

em (inch)

Treated with Parker A Phosphate. (Bonderit 37)

Zinc vapor on untreated A steel plat- zinc vapor B animals

In the laboratory arium phos- ■, B phated. , Zinc vapor

Zinc vapor on In the laboratory A steel plat-. d. Dipping treated with B tied chrome

• zinc vapor. 0.53 (0.21 OJ
0.66 (0.260)

0.48 (0.190)
0.71 (0.280)

0.71 (0.280)
0.76+ (0.30O ₊ .)

0.71
0.76

0.280)
0.300)

75 75

100 60

50

50

50 20

cm / kg (inch pounds)

23 34

46 (40) 23 (20)

46 (40) 23 (20)

68 34

V-notch test % loss when wrapping around the vertex of the notch

100 100

100 100

100 25

90 20

Electrolytically treated with duplex chrome
Zinc vapor

A 0.73 (0.290)
B 0.76 ^ (0.300+)

30 10

68 (60) 23 (20)

25 10

7522 Uq

Example 5

The following example serves to demonstrate the advantage of the duplex electrolytic chrome coating according to the invention when applied to zinc-plated steel * galvanized steel and zinc-vapor-plated steel (all according to Table III). This special duplex coating is evaluated comparatively with reference to such samples as, for example, otherwise treated zinc-coated steel and zinc coatings over steel that has been coated with phosphate or has been coated with Ohromat by immersion in order to prevent oxidative deterioration following the To prevent addition of the respective above-mentioned test paints to the test plate. The results of this evaluation are shown in Table VI. Part of the accelerated corrosion tests, the results of which are given in Table VI, is a 500 hour salt spray test which is evaluated for blistering the paint on the sample. This test is designated ASTM Standard Test D-714-. The same type of testing and evaluation is carried out for a similar test panel in a 500 hour humidity test where the test panel was exposed to humid air having a moisture content of 100 % relative humidity for 500 hours and then for the development of bubbles in the ASTH -Try - 56 was assessed in the prescribed manner.

The Salt Spray Test - This test is commonly used as a means of evaluating the corrosion resistance of painted panels that are exposed to a sharp instrument, e.g. Sharp scissors to cut through the coating on the base metal.

- 39 -

009886/1974

JFS 7522

Hi

Then the scratched plates are one through Air pressure compressed spray or mist on a 20% pure sodium chloride solution or a 5%. Sodium chloride solution containing the appropriate ion. This test will be done in a timely manner ranging from 150 to 500 hours of exposure, results obtained, whereby the test is considerably shorter than in the case of the moisture test - the salt spray test is trained to handle the amount and rapidity of the To measure the deterioration of the undercoat of the paint film in a corrosive atmosphere. After suspension |

be the scored plates with the edge of a flat one Knife or spatula scratched under a stream of water until the lugs or protrusions have been scraped off and vigorous scratching does not remove any additional paint. The salt spray test primarily evaluates the metal finish rather than the final organic coating itself as it is the Inability of the coating associated with the organic paint to reduce the spread of corrosion under the paint film.

The 500 hour moisture test - in the moisture test, the coated panels are divided into Λ two test series, one of which is scratched and the other test series is not scratched, but is evaluated with regard to the formation of bubbles (ASO) M D-735-62). The panels are exposed to an atmosphere maintained at 100 % relative humidity l) at 35 ° C (95 ° F). The saturated moisture atmosphere by atomized water at atmospheric pressure in a cell of such training ■ that Oi e may represent a Salzeprühzeile simultaneously maintained. When testing moisture, the permeability of the paint

0098 86/197 4

JFS 7522

films from the extreme against moisture-laden air Importance * Although the paint film is highly protective, it is reasonably permeable to Vasserdarapf. When moisture penetrates the paint film, it hits the coating associated with the paint. At this point it shows the quality of the surface preparation itself. A failure in the moisture test is essentially through the blistering appears, in the form of tiny needle point bubbles or more extensive, larger bubbles is present. The assessment applied to the panels, Scoring system consists of counting the size and the extent of these occurring on the paint film Bubbles according to ASTW D-714-56.

ORiQiNALiNSPECTED

Zinc bond ■ base
(with zinc 'plated steel)

Painting specification
(Faintlok)
control

2? abe 1 1 e VI Results obtained by series of the "accelerated corrosion test3

Metal and 500 hours Salt pan test 500 hours ro
ro
Moisture . ■ ■ treatment test Bows ■ ■ '* To creep value d. Blistering Creep value Blistering struck Eitzung in (ASTH D-735-62) ν.d. meeting (ASTM D-714- ... 1.6 mm in 1.6 µ 56) , (in Sexteenths (Sixteenths of an lixch) of an inch) ■ ■ ■. . ■ or% Ver lust after Tape application

annealed »zinc bond

In the laboratory
Dip chrome treated ¹ zinc "bond

Electrolytic m.Duplex chrome treated ear zinc bond

Commercially available phosphated Zinc on steel

Entire coating film Entire coating film

7 6

Insurance 50% loss Deterioration $ 0% loss

OK (none) OK Blow (few) 10% loss

8 7

10 8

C none)
(no)

Alright ^
(no)--
Venous bubbles

Okay ^ • (none) .— " - 1% loss

75% loss 100% loss

Tight tight

Ok, mean co value

Okay (none) okay (none)

Venous bubbles Dense bubbles

Table VI

(Continued) 500 hour salt spray test

Legs

Metal and
treatment

Eriechwert v.d.

stroked tick in 1.6 mm (in sixteenths
of an inch)

500 hour humidity test

Blistering creep value (ASTM D-735-62) from session

in 1.6 mm (sixteenths of an inch) or % loss after tape application.

Blistering (ASTM D-714-56)

_o Galvanized untreated A ο Steel base B

to location

o & ■ .

ai Electrolytic A

^ m. duplex chrome B

-" * treated

• 4> He phosphates A

coated with zinc. B ζοgener steel

With zinc- Untreated with A vapor plat- Zinc vapor plat- B steel-plated
basis

Coated with zinc vapor B in laboratory A
phosphate!
Steel total paint film deterioration 100% loss film deterioration 100% total paint film loss

Few bubbles
Few bubbles

In order
In order

Total painting film

Overall paint film OK (none)
Okay (none)

Okay (none)
Okay (none)

Dense bubbles Dense bubbles

Okay (none) okay (none)

OK (none) medium number of bubbles

Deterioration 100% loss of density bubbles Deterioration OK Few bubbles

2 1 bubbles
blow

(no)

Alright ^

(no)

50 % loss

Okay ^ (none) - Dense bubbles

O? at el I e YI
(Continuation)

500 hour salt spray test

Rows

Metal and treatment

At- . Creeping eyelid.

stroked session in 1.6 m

(in Sixteenths of an Inch)

5ÖÖ hour humidity test

Blistering odor value (ASOJM D-735-62) y.d. scoring

in L, 6 mm (sixteenths of an inch). or % loss after tape application

In laboratoium A through diving B with chrome "treats vapor-deposited zinc

Electrolytically A treated with duplex B chrome! vapor-deposited zinc

4 2

2 2 bubbles
blow

Okay ^)
(no) -
Few bubbles

Blistering (ASTM D- 714-56)

OK (none *.) OK (none)

Alright (none) Alright (no )

Alright ^

(no)-

blow

Alright (none) Alright '(none)

. _Ur 2011773

JS ¹ S 7522 'T *

The accelerated corrosion test data in Table VI above shows the improvements in under-film corrosion resistance, and the paint adhesion properties brought about by the duplex chrome plating zinc deposition were markedly superior to those with phosphate coatings in terms of moisture and the same as these phosphate coatings in terms of moisture content Behavior in the salt spray medium.

While the foregoing examples and general description of the invention, duplex chrome coatings specifically have described that by using a sulfate ion activator, z. B. an activator derived from sulfuric acid, it is broadest Within the scope of the invention that other equivalent activator ions ζ. The chloride ion derived from hydrochloric acid or a water-soluble salt thereof, in a similar manner Way can also be used to the simultaneous Deposition of the duplex coating in connection with control of pH, current density and other parameters of the present process. Hence, when the term chromium activator substance is used in according to the claims that not only the sulfate activator material is used , but other equivalent functional materials, e.g. B. the chlorides and any other ' Ions that act in a similar manner include.

The following examples serve in particular to illustrate the use of the chloride ion or the JPluoroborate ion in the method according to the invention

009886/1974

JFS 7522 h

Be 1 s ρ i e 1 6

Using the chloride ion in place of the sulfate ion, an electrolytic treatment bath was prepared with chromic anhydride at a concentration of 30 g / l. The chloride activator material, e.g. B. hydrochloric acid, was added in proportions such that a ratio of chromic anhydride to chloride ion of 300: 1, 200: 1, 100 s 1, 50: 1 and finally a ratio of 25 % 1 was obtained. In each of the experiments the bath temperature was similar at room temperature and the acidity values at a pH value below 1.0 maintained at the corresponding proportions shown.

Zinc bond plates measuring 7 »6 cm (3 inches) wide χ 17 »8 cm (7 inches) in length, which is about 4, 6 ^ u (180 millionths of an inch) had zinc metal electroplated on each side were degreased in acetone, in dilute acid activated, rinsed in water and cathodically treated in each test bath. The treatment current density was at 50 A / 0.09 m- (amps per square foot) and the Bath immersion time was maintained at 4.0 seconds. This treatment is a treatment extent of 200 coulombs / 0.09 m (coulombs per square foot) of the treated ^ delta surface area equivalent.

The ghrome coatings deposited on the various test strips were with regard to their chromium components and their weights were analyzed and their ability to resist corrosion in the 5% salt spray test described above to withstand valued. Furthermore, these test strips were used as a basis for painting the Olsen Button test and the reverse impact test,, also rated as described above.

009886/1974

.JFS 7522 H ^

The values obtained as a result of this test showed suggests a duplex chrome plating with good protection against corrosive attack and excellent paint adhesion properties are equally good from a ghrome coating bath, the one chloride ion activator as well as the sulfate ion activator, used in the preceding examples of the method.

The following data listed in Table VII are used to illustrate the set of results obtained in the test procedures referenced in this example

- 4-7 -

009886/1974

origwal inspected

treatment

Table VII

of zinc bond test plates with a chromic acid bath (30 g / l) with variable chloride concentration

VJl tV)

Chrome bath

concentration

egg

CrO ₃ ZCl

relationship

Chromium coating weight mg / 0.09 m ^ "~~ (milligrams per Sq.Ft.) paint (metal) (oxides) (total) Samples coated with alkyd-based paint. '. ■■■" Plate 5% (DuPont 707 - 25 / i (1.0 mil)

• PnftWn 52 »-» 1 4t 04-ϊίτ »1> -ο. '

strength

Cr

3 + 6

CRT spray medium
z. Suction
v. 5% Eotrost d.
basis
hours

Olsen Button reverse % Loss in impact test

Tape application

■ 30/0 1/0 I. 30 / 0.10 300/1 30 / 0.15 200/1 3O / P, 3O 100/1 O 30 / 0.60 30/1 O
CO 30 / 1.2 25/1

1Λ
1.9
1.6

1.1
0.8

0.7

Ό, 9
11.6
16.4

27.9
34.0
22.0

2.3 13.5 18.0 29.0 34.8 32.7

light gray 135

gray 170

yellow brown 175

light gold 186

gold 171

gold 177

55
25th

15th
20th
20th
28

for ice formation * cmkg (inch, lbs)

68 (60)

68 (60)

68 (60)

68 (60)

68 (60)

68 (60)

Zinc bond comparison (no chrome coating) 35

23 (20)

JFS 7522 ^

From the data in the table above it can be seen that, in comparison with the control sample, a test sample treated with duplex chrome gives an improvement of 15 hours in terms of corrosion resistance when placed in a chrome bath with a ratio of chromic anhydride to chloride ions of 100: 1 has been treated. It is interesting that at a ratio of 300 parts of chromic anhydride to 1 part of chloride ion activator, the improvement in corrosion resistance is still very high, on the order of about 135 hours to deposit a mixed coating of chromium metal and chromium oxide, which results in a significant improvement in terms of corrosion protection compared with the control sample. From the test data that were obtained with regard to the adhesive bond strength tests, it can be seen that the percentage of paint _{loss in the #} Olsen Button test by using a chromium coating bath in the chloride ion activator in a concentration of only 1 part chloride ion to 156 parts hexavalent chromium ion or 300 parts chromic anhydride is present, goes back to at least half. It is also noteworthy that by using the duplex coating created by using chloride ions to aid the simultaneous deposition of metallic chromium under the pH conditions specified there, there is a significant drop in the percentage recorded by the Olsen Button test Loss results, taking samples consecutively with a 25 yU. (1.0 mil) thick coating of DuPont 707 alkyd based paint.

The following example serves to explain another one

'- 49 - · ■' ■ '■

009886/1974

JFS 7522 '

Embodiment of the invention, wherein the method is the Fluoroborate ion (BF ^ -) instead of either of the above sulfate ion or the chloride ion described as activator ions for the chromium coating.

B e is ρ ie I 7

A series of chrome plating baths at 30 g / l Chromic anhydride (CrO,) and various concentrations made of fluoroboric acid (HBEV) so that ratios from CrO, to BF ^ ranging from 300: 1 to 25 J 1 were obtained. ,

Zinc bond plates were degreased in the usual way, activated with an acid activator and with chromium at current densities of 50, 100 or 150 A / 0.09 πι (amps per square> foot) covered. The baths were kept at room temperature and at a pH below 1.0 operated. .

The test results of this procedure using of the fluoroborate ion as an activator substance indicates a successful operation of the method. The one in table VIII listed following data describe the composition of a duplex bicomponent coating, which is based on a Zinc bond was deposited from a bath, in which the ratio of chromic anhydride to fluoroborate ion at one Value of 25 J 1 is kept. The current density of the electrolyzing bath went from 50 A / 0.09 m to 150 A / 0.09 m (ampt per square foot) varies. With the high current density the oxide content of the coating decreases with respect to the amount, and the metallic content of the coating increases with respect to the amount, as can be seen from an examination of the results in the following data.

- 50 "

009886 / 197A

JFS 7522 '

6th 300 2.3 - 2O> 7 23.0 3 300 3.0 15.2 18.2 2 300 3.2 11.6 14.8

there would be VIII

Treatment of zinc bond plates with a chromic acid bath 30 g / l) with 1.2 g / l fluoroborate activator

Power handling Coulomb / ear coating weight

density ρ recovery time 0.09 m ² ^ mg / O, 09 m ^ (milligrams per

A / 0.09 nr seconds (per Sq.Ft.) '■

(amps per Sg.Ft.) (Metal; (Oxide; (Total) Sq.Ft.) Cr ° - Cr ^{5 + 6} Cr ¹

50 100 150

Example 8

The following example describes a series of pilot plant trials using 25.4 cm (10 inch) wide zinc-coated blasting strips and 0.61 mm (0.024 inches) thick cold rolled steel in the form of spirals, where each coil weighed about 900 kg (2000 lbs.) The temperature of the chrome plating bath was controlled at about tree temperature and the pH was adjusted to below 1.0. The concentration of hexavalent chromium was 15.6 g / L, and that ratio of hexavalent chromium ion to SuIfataktivator-dione was about 26: 1st

In a series of semi-technical experiments, zinc bond and cold rolled steel coils under various treatment conditions in the following Table IX chrome plated areas indicated. Samples of each coated material and for each treatment feed condition all showed satisfactory corrosion resistance,

009888/1974

JFS 7522

Paint adhesion and weldability. The following data were obtained:

T a b e 1 1 e IX

Conditions and values

Zinc Bond spirals area

Row speed 6 to

m / min (ff./min.) current densities.

A / 0.09 m2

(Amps per sq. Ft.) Treatment level

ΟομΙ. / Ο, Ο ^ ο « ¹ (coul./ft. ^D )

(20 to 50) 50 to

Cold rolled steel spirals

area

10.5 to (35 to 50Y

80 to

75 "to 500 115 to

, Ohromüb erζ ugswerte;

Total weight mg / 0.09M ² 4.0 to 20.0 4.0 to 12.0 (mg / ft.2)

Ratio 1/2 to 1/8 1/1 to 1/3 Cr ^{i + b} (0xid). .

Legal liability (DuPont 707) Weldability

good to good to excellent draws

excellent excellent

It was found that the properties of corrosion resistance and dye adhesion of ferrous and non-ferrous substrates by application of a composite Coating made of zinc-containing material, followed by a coating of tin-containing material, then a coating made of a chromium-containing material or a composite coating made of tin-containing material followed by a coating of chromium-containing material can be significantly improved. It was in particular good corrosion resistance to salt spray

- 52.-

009386/1974

Ji S ¹ 7522

achieved by adding a steel substrate with tin, subsequently was coated with duplex chrome and zinc, then with tin and then with duplex chrome. The zinc component is typically electroplated or hot dipped zinc. For example, the Tin component from stone or matte (matt) or re-flowing tin or tin alloys, such as Sn-Zn, Sn-Ni or Fe-Sn exist. It has been found that it is particularly beneficial to deposit a tin coating by replacing some of the underlying zinc with tin in a halogen bath. On the other hand are Hot upsetting or electroplating of tin suitable, e.g. the deposition of tin alloys from common alloy electrolytes, such as tin-nickel, tin-zinc and tin-iron. The chrome or duplex chrome components of the composite coating may be commercially available from by the duplex chromium deposition technique noted above standing tin-free steel baths, conventional chrome baths or a conventional chrome bath with a subsequent chemical immersion or plating treatment.

The following table lists the hours up to 10% hot rust formation for various coatings on a steel base.

- 53 - - "■■■ -

009886/1974

O? a b el 1 e X

-

CD OO 00

Substrate (steel base)

+ Duplex chrome

+ 0.11 kg (1/4 Ib.) Stone pewter (38 cm χ 10 " ⁶ ,

15 microinch.es)
4 · Duplex chrome

+ 0.11 kg (1/4 Ib.) Re-flowing tin

(38 οιη. Χ 10-6, 15 microinches) + Duplex chrome

+ electroplated zinc (102 cm χ 10,

40 microinches)
+ Duplex chrome

or

+ tin coating applied by immersion for 2.0 seconds (halogen bath) + Duplex chrome

+. hot-dipped zinc (1020 cm χ 10 ", 400 microinches, regular tinsel) + duplex chrome (5.0 mg / 0.09 m ² )

or

+ tin coating applied by immersion for 6.0 seconds (halogen bath) + duplex chromium (10.0 mg / 0.09 m ² )

Hours until 10 % red rust forms

2 - 5,

2-3 200

2-3 200

-

4.5 200

127

295

JFS 7522 SX ',. ,

The first entry in the table is duplex chrome directly over a steel base, and the number of hours it took for 10 % red rust to form ranged between 2 and 3 hours. As noted above, it has been found that the time to reach a given percentage of red rust for a duplex chrome plating directly over steel does not vary significantly with plating thickness. The second item in the table shows that a steel base coated with tin (perforated or stone tin in its pure form or as it is) provides approximately the same protection up to 10% rust formation. If the. Tin plating is followed by a duplex chrome plating, but the corrosion resistance is considerably improved, and it has been found that the protection is over. Tin alone has been improved by about 200 hours.

The next entry in the table shows that refluxing a Tin (initially deposited stone tin, which is used to form an alloy, then flows again) the same amount in protection against red rust results in like stone pewter. In turn protection against red rust formation is provided by applying a duplex chrome coating in the tests carried out considerably increased to about 200 hours.

It was found that electroplated zinc directly over steel gave about 4x hours of protection to the formation of 10 ~ % red rust. However, when the electroplated zinc is coated with duplex chrome, the protection has been found to extend from about 25 to 65 hours. If the electroplated zinc is coated with tin, the protection against red rust formation is not increased significantly. However, if a duplex chrome coating is applied after the tin coating, it has been shown that the protection against the formation of liotrost is significantly increased

- 55 -

009886/1974

Ji ¹ S 7522 b ? \

to 200 hours before a red rust formation of 10 % occurred.

As can be seen from the last information in the table, hot-dipped zinc over steel provides protection up to the formation of 10 % rust for 93 hours. Duplex chrome over hot-dipped zinc extends protection to 127 hours. On the other hand, tin over zinc extends the protection to only ψν hours. It should be noted, however, that when duplex chromium is deposited over tin, which in turn is deposited over zinc, the protection against hot rust formation extends to 295 hours, a substantial and extraordinary increase.

The above table shows that a steel substrate coated with tin and duplex chromium or zinc plus tin plus duplex earpiece is considerably improved in terms of protection against rust formation.

For β ρ i el 9..

Samples of 0.11 kg (1/4 lb.) stone and reflowing tin (38 cm 10, 15 microinches thickness) are cathodic in a NagCO ^ solution at about 30 A / 0.09 m of the substrate cleaned for about 10 seconds. The cathodically cleaned samples are rinsed and immersed in a hydrochloric acid rinsing bath for about 2 to 3 seconds. The samples are then rinsed and squeezed and then in a duplex chrome coating solution (30 g / l -CrO ,, 0.3 g / 1 SO ^) at 100 A / 0.09 m ^{2 of} the substrate for 2.4 seconds electroplated. The samples are then pressed, rinsed with HCl (including rinsing with hot HCl) and then dried in hot air. The samples are then subjected to the usual salt spray test.

009886/1974

INSPECTED

JFS 7522 S "? ...

pulled. No 10% concentration occurred in the tests carried out Red rust formation on until after 216 hours of exposure to salt spray.

The above example shows the effectiveness of tin duplex chromium over steel substrate for salt spray resistance.

Samples made with zinc (electroplated and hot dipped) coated steel plates were degreased and placed in a

Pickled, rinsed and squeezed off with a hydrochloric acid solution. The samples were then immersed in a standard halogen bath (typically containing tin chloride, sodium fluoride, Containing sodium bifluoride and sodium chloride), in the case of zinc electroplating it becomes a single Dip used for 2 to 5 seconds, while in the case of hot dipped zinc, six 1 second dips be applied. The immersed samples are rinsed and squeezed, and then with an electrolytic Duplex chrome treatment machined as described above. Following the electrolytic duplex ghrome treatment the samples are rinsed and squeezed off and subjected to the salt spray test. How out

™ of Table X above, tests have shown that these treatments significantly improve the corrosion resistance.

-57-

009886/1974

GBSGINAL INSPECTED

JFS 7522

Treat unp; s device

Figs. 1 to 4 show a treatment device for Implementation of the method according to the invention. The device shown is particularly for "coating" Strips suitable, e.g. B. Steel strips that have a starting zinc coating exhibit on it. The strip is designated 10 and is shown moving over a first contact roller 12, which is arranged to rotate about a shaft 14, is guided * The strip moves around the roller 12 and extends downward between electrodes 32a and 32b into a treatment chamber or tank 16 in which an electrolytic solution 18 is included. A lowering or The dip roller 20 is near the bottom of the tank 16 and is mounted for rotation about a shaft 22. The shaft 22 is held by supports 24a and 24b, which in turn are mounted in a frame structure 26a and 26b are. After revolving around the sink roller 20, the strip 10 migrates upwards between the electrodes 34a and 3 ^ b of the chamber 16 and partially around a contact roller 28 which is rotatably arranged around a shaft 30.

Mounted within the container 16 is a first anode structure made up of anode members 32a and 32b disposed on opposite sides of the strip 10 at the entry zone of the strip into the coating tank. A second anode structure JA- from-the anode elements 34a and 34-b is arranged in the tank at an exit zone from which the strip 10 emerges from the tank. The outlet anode elements 34a and 34b are also arranged on opposite sides of the strip 10.By attaching the anode elements to both sides of the strip, both sides of the strip can be

-58 -

• 009886/1974

JI ¹ S 7522

be pulled. The anode members 32a and 34a are mounted in the tank by mounting and insulating members $ 6 and 38. Similar mounting and isolating elements 40 and 42 are used to attach the anode elements 32b and 34b to the brackets 24a and 24b. The mounting and isolating elements 38 and 42 at the bottom of the anode elements also serve as a cover to prevent the flow of current to such parts of the strip in FIG the bath which are not adjacent to the anode elements. Additional cover members 43a and 43b (Figures 2 and 3) are used between the anode structures 32 and 34 to prevent bipolar action and current leakage that can occur when cladding one or both anode structures.

Each anode element is designed to be separate with positive current from a direct current source, not shown is supplied. The negative current from the same source is passed to the strip 10, in a special way the contact rollers 12 and 28 out. Thus, the strip 10 serves as an electrical cathode in the plating system, during one or more of the anode elements 32a, 32b, 34a and 34b serve as an electrical anode.

The above described in connection with the examples, electrolytic solution fills the tank 16 to the level indicated in the drawings. The extent to which the Immerse inlet and outlet anode structures 32 and 34, determines the effective coating length of the bath. The line 50 serves as a drain.

One of the anode elements, e.g. B. the anode element 32a reproduced in FIG. 4. It has mounting brackets 32a-1

- 59 -

009886/1974

JFS 7522 ';

and 52a-2, by the anode members on the mounting members 56 defining the anode structure are attached.

A pair of nip rollers 54a and 54b are arranged above the exit zone of the coating tank in order to remove excess Remove coating liquid from strip 10 as it exits the tank.

In operation, the strip is fed through the tank in order to to make a coating on it. One or more anode | elements are operated to produce the desired coating. In particular, one or both of the anode elements 52a and 54a connected so that the electroplating current flows from there when it is desired to coat the underside of the strip 10. One or both of the anode members 52b and 54b are energized to derive electroplating current therefrom, if the top of the strip is to be coated.

In some cases it has proven to be useful to energize only one or both anode elements either at the entry zone to the tank or at the exit zone from the tank, but not λ in these two zones. If only one or both of the entry anode elements 52a and 5 ^ b are energized, portions of the strip will be electr plated once they are immersed in the coating solution. Portions of the strip, once past these entry anodes, actually receive no electroplating current. These parts of the strip are thus electroplated after the first immersion, after which the immersion is continued with practically no further electroplating. Some dew coating of the strip may occur during this immersion process.

.60 -

Q09886 / 1974

JFS 7522 ΦC

which is different from the electroplating process.

On the other hand, if only one or at.de of the exit anode elements 34a and 34b are energized become parts of the strip is first immersed in the coating solution, continuing the immersion until finally electroplating takes place when these parts pass through the exit zone past the anode elements 34-a and. 3 ^ -b wander. That prior immersion prior to electroplating may introduce some dip coating.

It was found that the coating on the * strip with respect to the thickness and color will vary depending on whether the electroplating is on the entry zone or on the Exit zone of the tank takes place. Steel strips 25 cm wide, both in the uncoated state and in the with Zinc coated condition, were treated in the device according to FIGS. 1 to 4. The total effective plating length between the inlet and outlet anodes was about 0.6 m Anodes, changes in the bath volume only change the path length that is available for electroplating · In a number of experiments conducted, the effective electroplating length has been found to be from 0.15 m (0.5 feet) to varied to a maximum of 0.6 m (2.0 feet), giving a clad length to immersion length ratio of 1: 8 until 1: 2 was set. It was found that on a steel plate coated with zinc there was a ratio a plating length to immersion length of about 1: 4 along with delayed wiping off excess over- ' pull solution from the strip and rinse the solution off of the treated surface, an increase in the weight of the oxide component of the chromium coating and a change in the Color of the coating from gray to brown. In the event of

- 61 -

009886/1974

JFS 7522 *

Changes in current density from 50 to 200 A / 0.09 m (amperes per square foot) of the strip and in the case of a

samtbehandlung up to 300 coulomb / 0.09 m (coulombs per square foot) weighed on the ER-coated steel with zinc

Chromium coatings A produced up to 22 mg / 0.09 m (mg per square foot) and contained a weight ratio of chromium metal to oxide of 1: 2 to 1: 8. These coatings were found to provide good corrosion resistance and good paint adhesion.

Another set of tests performed on uncoated steel showed that the order of electroplating and immersion affected the composition of the chromium plating constituents and color. Duplex coatings with a 1: 4 weight ratio of chromium metal to chromium oxide of bluish color were produced using only entrance anodes 32a and 32b and the strip was run through the solution past exit anodes 34-a and 3 ^ b, which remained without electricity (sequence! immersion and simultaneous electroplating with subsequent immersion without electroplating). It was found that after reversing this procedure, namely by leaving the inlet anodes 32 and 32b de-energized and the electroplate. n ^ was carried out only with the exit senodes 34-a and yVo-- (sequence! first immersion, then later electroplating), bright metallic gray coatings with a weight of 4 to 12 mg / 0.09 m were obtained, which had a weight ratio of Chromium metal to chromium oxide of about 1! 1. All of the coatings produced in this way in this test series had good paint adhesion. It should be pointed out that in the case of duplex coatings over zinc, bluish and gray colors were obtained in the same corresponding sequence as stated above.

JFS 7522 W .- ■ '".

Improved welding performance

A series of tests carried out showed that, when duplex chromium coatings were used according to the invention, the life span of welding electrodes in the welding equipment used for welding of steel, the cast made with such coatings, ⁿ over those without such coatings significantly increased was. In particular, in an experiment carried out, over 7000 individual resistance welds were carried out with welding electrodes without any noticeable deterioration in the electrodes. In this experiment the welded steel was coated with a zinc electroplating which had a duplex chrome top coating. A weld force of 181 kg (400 pounds), a weld time of 10 cycles, and a weld current of approximately 11,000 amps were used.

Relationships of the process parameters

Figures 5 through 12 contain curves resulting from the analysis of the coatings produced according to the invention developed data, ' in particular with regard to the change in various process parameters, graphically.

Figures 5 (A and B) show the effect of stripe speed, current density and the ratio of CrO,; SCL. Part A of Figure 5 gives the weight of the chromium oxide component. partly in mg / 0.09m (mg per square foot) against the ratio of CrO,: SO ^ for different current densities, which results from the curves. The curves in Part A all relate to a total coulomb treatment height of 200 coulombs / 0.09 m (coulombs per square foot) of the substrate and a strip speed in the coating

- 65 -

009886/1974

JFS 7522 ^ S. -

solution of 15 m / min (50 feet per minute). In the tests carried out, coated strip samples were each bent into the shape of a cylinder, which in the solution at a predetermined peripheral speed during of the coating process.

Part B of Figure 5 contains a series of curves developed in the same way as the curves in Part A except that in this case the strip speed in the coating solution is 90 m / min. (300 feet per minute). A comparison of parts A and B Λ shows that if all other process variables

si ^ ch
remain constant, an increase in the strip speed will result in an increase in the weight of the chromium oxide component deposited in the coating. For example, at a strip speed of 15 m / minv (50 feet per minute), a ratio of CrO,.: SO ₂ ^ of 100: 1 and a current density of 100 A / 0.09 m, about 4 mg of chromium oxide component per 0.09 m (square foot) of substrate as shown in Part A. With reference to Part B, for the same process conditions with the exception of an increase in speed of 90 m / min (300 feet per minute), approximately 8.5 mg of oxide component are deposited per 0.09 m (square foot) of the substrate " ™

• » ^: ■ - ■

The effects of varying the current density are in each the curve inserts of part A and B of FIG. 5 reproduced. For example, it is assumed from the curves in part A. a ratio of CrO: SO ^ of 100; 1 can be seen, that when the current density goes from 300 to 200 to 100 to 50

ο yourself

A / 0.09 m is reduced / the resulting chromium oxide components increase in the coating accordingly from about 1.9 to about 2.7, 4.0 or 5.4 mg / 0.09 m of the substrate,

• i ■

- 64-

009886/1974

JFS 7522

Both sets of curves of parts A and B of Fig. 5 also show the dependence of the relationship between the chromium oxide constituents in the coating on the ratio of CrO 1: SO 1, with all other factors remaining constant. For example, in part B the curve showing the relationship for a current density of 50 A / 0.09 m ² shows that the chromium oxide components of about 17 mg / 0.09 m with a ratio of CrO,: SO ^, varied from 50: 1 to about 7 mg of oxide components per 0.09 m of substrate at a ratio of 200: 1.

The curves of parts A and B of FIG. 5 show that the Oxide constituents in the coating increase with (1) increasing the stripe speed, (2) decreasing the current density and (3) lowering the ratio of CrO,:

The curves of Figure 6 illustrate the relationship between the ratio of caustic soluble to caustic insoluble chromium components as a function of current density for various chromic acid: sulfate bath ratios. The curves give a total coulomb treatment ^{height of 200 coulombs / 0.09 m 2 of the} substrate. The curves of Part A in Figure 6 were developed for a strip speed of 15 m / min (50 feet per minute) during the coating process, while the curves of Part B for a strip speed of 90 m / min (500 feet per minute) - were developed. As can be seen from a comparison of Parts A and B, the ratio of coating ingredients soluble in caustic agents to insoluble in caustic agents increases as the strip speed is increased, with all other process conditions remaining constant.

- 65 -

009886/1974

JFS 7522

For example, with a ratio of GrO, J ^ of 50 i 1 and a current density of 100 A / 0.09 m, the curve of part A, which shows a strip speed of 15 m / min. (50 feet per minute) represents that the ratio of ingredients soluble in caustic agents to ingredients insoluble in caustic agents was about 1.9. For the same conditions, except for a strip speed of 90 m / min (500 feet per minute), the ratio resulting from Part B was about 5-60. Each of these series of curves for parts A and B shows that as the current density increases, the ratio of chromium components soluble in caustic agents to insoluble chromium constituents in the coating decreases.

7 contains curves which show the influence of the Coulomb treatment level on the deposition of the chromium components. The curves were for a ratio of CrO ₂ . : SO ,, of 50: 1 at two different current densities of 50 and 100 A / 0.09 m ^{c of} the substrate. The upper curve, showing a solid line, gives the total weight of the soluble chromium constituents (C.

in the substrate in mg / 0.09 m (mg per square foot) against the treatment height for a current density of 50 A / 0.09 m. The lower, formed as a continuous line, gives the weight of the insoluble chromium component (Cr ⁰ ) for the same current density. The two dashed curves against the weights of the soluble and insoluble chromium components at a current density of

100 A / 0.09 m again. It should be noted that if the total Coulomb treatment level drops, so do the weights of the soluble and insoluble coating ingredients go back. It is assumed that a treatment height e of 20 coulombs / 0.09 m of the substrate a practical minimum

_ 66 -.

Q09886 / 197V

It

JFS 7522 represents the dest-Coulomb treatment height.

Since the current density is constant for each curve in FIG. 7, the coulomb height at any point in the _A curve is the treatment time and hence the coating thickness

2 2

equivalent, since A / m χ time in seconds equals Goulomb / m is. Examination of the curves in FIG. 7 reveals that, ■ as the goulomb height increases and the coating becomes thicker at the same time, the speed increases both Components does not change significantly. About the same ratio of soluble component (oxide) to insoluble constituent (metal) is present in all Coulomb values. This shows "that for all-Coulomb values both oxide and metal are deposited, thus creating a mixed duplex coating is, in contrast to a coating of discrete, separate layers of oxide and metallic material.

Figure 8 gives the weights of the chromium components in the coating (ingredients soluble in caustic agents and insoluble in caustic agents) as a function of Ratio of CrO,: SO ^ for different chromic acids

(CrO,) concentrations again. The curves marked with Gr ⁺ ^ represent the constituents soluble in caustic agents (chromium oxides), while the ^{curves marked with Cr 0} represent the constituents insoluble in caustic agents (chrome metal). It can be seen from Fig. 8 that the insoluble chromium constituents remain pretty much the same with variations in the ratio of CrO,: SO ^, from 300: 1 to 25 sec. These curves also show that for a given ratio of CrO,: SO ^ the deposition

009886 / 197A

JFS 7522 QfH ■■ '.' ■

effectiveness of those insoluble in caustic agents and soluble chromium components from 15 to "40 g / l solution increase while the chromium oxide deposition is in the range of ^ about 3 »5 to about 7> 5 mg / 0.09 m ■ for the same increase the CrO ^ concentration.

The curves of Figure 9 show the effect of bath temperature on the weight of the coating components. The curves were

• 2

at a treatment value of 200 coulombs / 0.09 m and at two different ratios of CrO,: SO., of 50: 1 and 100: 1. The curves of parts A and B relate to a coating bath ratio of 50: 1 and accordingly represent the coating weight versus the current density of the constituents soluble and insoluble in caustic agents. The curves in parts C and D refer to a ratio of CrO,: SO ^ of 100: 1. The curves in each part of the figure show the relationship of the weight of the component versus the current density for two different bath temperatures, namely 66 ° C (150 ° F) and room temperature. It is evident that the bath tempera generally has a greater effect on the constituents insoluble in caustic agents than on the constituents soluble in caustic agents. The curves of parts A and G of Fig. 9 are generally close together at different bath temperatures, while the curves of parts B and D are quite far apart for the different bath temperatures. For example, at a current density of 100 A / 0.09 ra and a bath ratio of 50: 1, the constituents soluble in caustics are roughly in the vicinity of 5 mg / 0.09 m for two different bath temperatures, as shown in Part A. However, the caustic-insoluble constituents of agents at the same current density and the same bath ratio in the area of 5 1/2 mg / O, 09 m at a bath

JFS 7522

To

temperature of 66 ° C (150 ° F) and at a lower

Value of rand 3 mg / 0.09 m at room temperature.

The curves in FIG. 10 show the influence of the current density on the coating components. The one solid line The curve showing the coating weight in mg / 0.09 m of constituents soluble in caustic agents versus the current density, while that as a dashed line The curve shown shows the relationship for the coating constituents which are insoluble in caustic agents. Be it notes that in the area a current density of

6 A / 0.09 m, both parts of the coating should fall off. It it is assumed that the lowest practical current density,

which can be used in the area of 6 A / 0.09 m lies.

Fig. 11 shows the influence of pH on the weight of the coating components. The one from the solid line existing curve gives the relationship between weight and pH for those soluble in caustics Coating constituents again, while the curve shown as a dashed line shows the relationship for those in caustic Agent reproduces insoluble constituents. It should be noted that the weight per unit area both the soluble and the insoluble constituents fall sharply with increasing pH. It is believed that a pH of about 2.0 is a practical upper limit for any duplex chrome plating process.

All of the curves listed above generally show the relationships between the various parameters of the coating process. As indicated above, it is generally believed that the level of pH is below about 2.0

- 69-

009886/1974

JFS 7522

must be kept. At a pH above about 2.0 there is practically no deposition of the caustic Agent of insoluble chromium component (chromium metal). The pH limit on the lower side is determined by the Determined concentration of chromic anhydride. It is believed that maintaining the pH below about 1.5 is preferable.

As also stated, the current density should be above about

P-

6 A / 0.09 m of the substrate. The minimum current density is determined by the deposition voltage of the caustic Means insoluble constituents (chromium metal) regulated. The current density has no real upper limit. at Current densities were up to 600 A / 0.09 m. In practice, the upper limit with regard to the current density is determined by considerations, z. B. electrical contact roller capacity, line speed (line speed), bath movement and tank size determined. Although it is not believed that there is an effective limit on the Coulomb value, it is a minimum coulomb treatment value of about 20 coulomb /

0.09 w- of the substrate is considered appropriate.

The temperature can be varied over a wide range and is set at any suitable level, e.g. B. kept below 38 ° C (100 ° i ¹ ).

The concentration of hexavalent chromium ions in the coating solution should generally be above about 2.6 g / l be held in order to make the bath sufficiently conductive, so that no excessively high voltage is required for operation. There is no real upper limit as to the concentration of hexavalent chromium ions in the Solution, except for a limitation caused by the solubility

-70 -

009886/1974

of the material supplying the hexavalent chromium ions is determined. In technical operations, for example, higher chromic acid concentrations make the coating solution stronger viscous and increase the drag-out losses. Relatively high concentrations of 300 g / l of chromic anhydride were used in experiments.

The ratio of hexavalent chromium ion to chromium activator ion can vary over a wide range. At relatively high conditions, e.g. For example, over about 260 s-1, the deposition weight per coulomb electricity generally begins to decrease and the deposition efficiency may drop to an unusable level. At the lower end of the range, e.g. E.g., below about 5 > 1i, some kind of dip coating may take place in the event that a substrate is immersed in the solution which is not subjected to the electroplating action. The direct reaction that can take place between substrate and solution generally results in a sharp increase in the caustic solubles (oxide) and in the production of a colored coating. In experiments carried out, the ratio of hexavalent chromium ion to activator from a low value of about 1 s Λ up to a high value of about 520: 1 varies, 'and acceptable coatings were generated.

The duplex plating process is versatile and can be used to deposit a good quality chrome plating which can contain chromium components soluble and insoluble in caustic solution and in any desired weight ratio, preferably in the range of about M- : 1 to about 1:30 , contains.

The chrome coating weight and composition are given in

- 71 -

009886/1974

JFS 7522 &quot; ^

Relationship with the quality characteristics, e.g. B, weldability, corrosion resistance, abrasion resistance, paintability and the like. Coatings with a ratio of insoluble to soluble constituents of about 2: 1 to about 1: 15 with good overall properties can be produced over a wide working range. In order to obtain an improvement of a specific quality of the individual weights of the chrome components can be controlled to the desired ratio of insoluble to get to soluble component, by the bath composition and working conditions (typically current density and overall x g speed), depending on Need to be changed.

It was for example found that a duplex Ghromüberzug, the corrosion resistance is particularly suitable in terms without fiücksicht to the ability to apply a paint, the weldability or the abrasion resistance can be obtained when the weight ratio of Chrommetall- to Chromoxidbestandteilen in. The range of about 1: 30: 1 to about. 1 A coating which is particularly suitable with regard to the ability to apply a paint can be obtained when the weight ratio of metal to oxide is in the range from about 4: 1 to about 1: 5. A buplex chrome coating which is "particularly suitable with regard to weldability" can be obtained if the weight ratio of metal to oxide components is in the range from about 4: 1 to about 1:15 can be obtained when the weight ratio of metal to oxide is in the range of about 4: 1 to about 1: 2.

The color of the coating can also be determined by the ratio of Metal to be regulated to oxide in the plating, Sa was fixed-

- 73-

0098 «S / 197i BAD ORIGINAL

JFS 7522 MT

found that coatings directly over steel are a light, metallic gray color when the weight ratio from metal to oxide is about 1: 1 and that they are generally bluish in color when the wt ratio is about 1: 4. On the other hand, wise Duplex coatings over zinc coated steel a gray one

Color on when the oxide weight is less than about 7 mg / 0.09 m and the weight ratio of oxide to metal in the coating is less than about 2.5. If these coatings over zinc coated steel have an oxide weight above about 7 mg / 0.09 m and if the weight ratio from oxide to metal is above about 2.5, the color of the coating is blue-brownish to brown.

It is thus evident that the duplex coatings of the Invention over a wide range of properties can be varied to any number of quality standard values by changing any number of To meet process parameters.

Synergistic effect of zinc and chrome metal-chromium oxide coatings "

Figure 12 plots data showing salt spray life (hours of coating in salt spray medium before 5% hot rust is obtained) as a function of coating thickness. The lower curve in the figure shows the performance of a zinc electroplated steel plate. The upper curve in the figure shows the performance of a steel plate which is initially coated with zinc (electroplated) and then with a top coating of chromium metal-chromium oxides according to FIG. The one in Fig. 12 with "Duplex-Chrom

The point marked over steel "shows the jJotrostverninderode

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009886/1974

JFS 7522 '^

Performance of a duplex chrome plating directly over steel. It has been found that regardless of the chrome coating thickness, the time to reach 5 % red rust for a duplex chrome coating directly over steel is about 2 hours. One might expect that a duplex chrome plating over zinc would simply add a fixed fraction of the time to the protection provided by zinc alone. However, this is not the case, as can be seen from the curves in FIG. The difference between the upper and lower curves is not a fixed partial amount (of only 2 hours); rather, it varies from about 55 hours for a zinc thickness of 102 10 "cm (40 χ 10" inch) "to about 135 hours for a zinc thickness of 4-57 x 10" cm (180 χ 10 ^ "inch These curves explain the facts which were found in the tests carried out, namely that there is a synergistic rust-resistant effect of zinc and duplex chrome coatings.

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Claims (1)

7522 June 26, 1970 * Claims > j Process for depositing a corrosion- and abrasion-resistant, weldable and paint-adhesive Duplexr chrome plating on a metal substrate, thereby marked that (a) the substrate in a liquid solution, the ions containing hexavalent chromium and chromium activator ions of sulfate, chloride and / or fluoroborate ions, is immersed and (b) the solution with a direct current electroplating through the immersed substrate at a current density of at least about 6 A / 0.09 m (amperes per square foot) of the substrate, while keeping the pH of the solution below about 2.0 j for the deposition of a protective duplex chrome coating electrolyzed from chromium metal and one or more chromium oxides on the metal substrate. 2 · The method according to claim 1, characterized in that the chromium activator ions are supplied by sulfuric acid will. 5. The method according to claim 1, characterized in that the chromium activator ions are supplied by hydrochloric acid. 4. The method according to claim 1, characterized in that the chromium activator ions are supplied by fluoroboric acid will. Method according to Claims 1 to 4, characterized in that - 75 - ' 009886/1974 Ji ¹ S 7522 ^ '· that a liquid solution 'is used, which the hexavalent chromium containing ions at a concentration contains at least about 2.6 g / L solution. - 6. The method according to claim 1 to 5, characterized in that that the hexavalent chromium-containing ions by chromic anhydride in a concentration of at least about 5 g / l solution can be delivered. 7. Method according to claim 1 "to 6, characterized in that that a stream of holes in the range from about 25 to "about. ί 600 A / 0.09 m (amperes per square foot) of the substrate is applied. 8. The method according to claim 1 to 7 »characterized in that the electroplating current for a sufficient period of time to induce a treatment. of at least about 20 coulomb / 0.09 m (coulombs per square foot) of the substrate is supplied. . 9. Method according to claims 1 to 8, characterized in that the duplex chrome coating is deposited over zinc, tin or cadmium. M. 10. The method according to claim 1 to 9 »characterized in that the substrate during the coating process by the solution is moved. . · The method according to claim 10, characterized in that substrate movement in the range of about 6 to about 150 m / min (20 to 500 feet per minute) is applied. 12. The method according to claim 1 to 11, characterized in that a ratio of hexavalent chromium ent- - 76 - 008886/1974 JFS 7522 holding ions to chromium activator ions in the range of about 260: 1 to about 5 s 1 is applied. 13 · The method according to claim 1 to 11, characterized in that a ratio of hexavalent Chromium-containing ions are applied to chromium activator ions in the range of about 520: 1 to about 1: 1 will. Method according to Claims 1 to 13, characterized in that that the duplex chrome coating is uniform at a coating weight of about 0.5 "to about 65 mg / 0.09 m (mg per square foot) of the substrate is deposited. 15 · The method according to claim 1 to 13 »characterized in that the duplex chrome metal and oxide coating deposited on the substrate has a chrome metal content in the range from about 4 to about 80 % 16. The method according to claim 1 to 13, characterized in that the duplex chrome metal and oxide coating deposited on the substrate has an oxide content in the range from about 96 to about 20 % . 17. The method according to claim 1 to 13, characterized in that the duplex chrome metal and oxide coating deposited on the substrate has a weight ratio of chrome metal to oxide of about 4: 1 to about 1 »30 .. 18. The method according to claim 1 to 17 » characterized in that the substrate practically simultaneously 009 886/197 * JFS 7522 * "" * with the initial immersion L of the substrate in the Coating solution is electroplated with the substrate in the coating solution for a time after the electroplating has stopped remains immersed. 19 · The method according to claims 1 to 17t, characterized in that that the substrate is first in the coating solution • is immersed and remains in the solution for a predetermined period of time, and that after that Time to electroplate the substrate Removal of the substrate from the solution takes place. 20. Process for improving corrosion resistance a metal substrate, characterized in that that Ca) a zinc-containing coating is applied to the substrate, Cb) a tin-containing coating on the zinc-containing coating is applied and Cc) a chromium-containing coating is applied to the tin-containing coating. 21. The method according to claim 20, characterized in that steel is used as the substrate. 22. The method according to claim 21, characterized in that that as a zinc-containing coating. Zinc is used. 23- method according to claim 22, characterized in, that tin is used as the tin-containing coating. 24. The method according to claim 23, characterized in that that the tin coating is applied by replacing zinc in a halogen bath. - 78 - 009886/1974 JFS 7522 * 25 · The method according to claim 24, characterized in that that the chrome-containing coating is a duplex chrome coating, the chromium metal and one or more chromium oxides is applied. - 79 - 009886/1974