US3355268A - Corrosive protected composite having triplated nickel deposits and method of making - Google Patents

Description

Nov. 28, 1967 H. DU ROSE ETAL 3,355,268

CQRROSIVE PROTECTED COMPOSITE HAVING TRIPLATED NICKEL DEPOSITS AND METHOD OF MAKING Filed July 22. 1964 CORROSION QHROMIUM PLATE m w BRl6HT NICKEL PLATE ,.R.9I;E'PMQ%*E%%%ZI \NICKEL PLATE 1 1 7 METAL BASE CORROSION CHROMIUM PLATE -BRI6HT NICKEL PLAT NICK EL-MANGANESE ALLOY PLATE (0. ol-az MIL, 02596-47. MANGANESE) NICKEL PLATE F162 METAL BASE CORROSION T\ /CHROMIUM PLATE +BRI6HT NICKELPLATE F-N ICKE L MANGANESE ALLov PLATE (0.0/ 0.2 M/L., 025-42; MANGANESE) \NICKEL PLATE METAL BASE FIG. 3

ARTHUR HDUROSE AND KARL 8.WILLSON,1NVENTORS Wag... M73

Ahy

Patented Nov. 28, 1967 3,355,268 CORROSIVE PROTECTED COMPGSITE HAVING TRiPLATED NICKEL DEPOSITS AND METHOD OF MAKING Arthur H. Du Rose, Euclid, and Karl S. Willson, Cleveland, Ohio, assignors, by mesne assignments, to Kewanee Oil Company, Bryn Mawr, Pa., a corporation of Delaware Filed July 22, 1964, Ser. No. 384,457 11 Claims. (Cl. 29-1965) ABSTRACT OF THE DISCLOSURE The process and the new product produced thereby comprising the steps of applying by electroplating, from a nickel-containing solution, a first nickel layer onto a metal substrate, then applying an intermediate layer on said first nickel layer by electroplating from a solution containing nickel ions and manganese ions, and then applying a third layer on said intermediate layer by electroplating thereon from a solution containing nickel and sulfur.

This invention relates to a composite coating of adjacently bonded layers of nickel and more particularly to a composite coating of three layers wherein an intermediate layer thereof comprises a thin nickel deposit containing a desired amount of manganese.

In recent years much work has been done to provide an article with a decorative plate of chromium over two or more underlying layers of nickel. The composition and electrochemical properties of these layers of nickel are designed to obtain as good protection of the base surface against corrosion as possible without compromising the decorative appearance.

When using three layers of nickel, the composition of the intermediate layer is adjusted so as to be anodic to both the upper and lower layers and preferably the composition of the upper layer is adjusted so as to be anodic to the lower layer.

By the use of some triple-layer systems, marked cor rosion protection was effected (see Knapp, Trans. Inst. Met. Finishing, 1958, 35, 139-165). In most cases, however, the metal corroded too rapidly causing blistering or scaling or staining or colored the decorative surface.

Within the last few years triple-layer systems have been made using a nickel-containing deposit for each layer. Relative potentials of the layers have been controlled by the amounts of sulfur deposited with the nickel. The sulfur may be controlled in the deposits by adjusting the contents in the bath of the various organic brightening additives comprising sulfur with or Without additional sulfur-containing compounds. Sulfur-free brighteners with sulfo-oxygen carriers also may be used to supply some or all of the sulfur in the bath and hence in the nickel deposit. Thus, control of the addition agents in the bath may ultimately control or partly control the amount of sulfur in the electro-deposits and thereby the relative potentials of the deposits.

Several problems have arisen in connection with the triple-layer system because sulfur as such not only provides differences in potential in electro-deposits of nickel but also affects other physical properties such as ductility and brightness and continuity of the deposit. For instance, if the proper potential is to be maintained between the intermediate layer and the top layer, the sulfur contents of each layer must be controlled. However, the sulfur content of sulfur-containing nickel is limited and the potential tends to level off at sulfur concentrations in the range of from about 0.2-0.3 percent by weight. Thus the degree in which the concentration of sulfur in the deposits may be varied in the nickel layer to adjust potential is very narrow. Moreover, if a plater prefers to deposit a lower layer of nickel from a sulfur-containing bath, he may have to increase the amounts of sulfur in the intermediate and upper nickel layers.

It has now been discovered that in triple layer systems having manganese-containing intermediate layers, such manganese-containing layers are strongly anodic to nickel and can be used effectively as sacrificial layers in the three-layer group, nickel, nickel-manganese, nickel. Such layers may be deposited from any common nickel plating bath, such as a standard Watts type bath having the proper concentration of a water-soluble manganese compound.

In accordance with the present invention there is provided an improved composite coating comprising three adjacently bonded layers of nickel deposits, the lower layer being a conventional low-sulfur or sulfur-free nickel electroplate preferably 0.3 to 2 mils thick and having from 0 to about 25 percent, preferably from about .1 percent to about 25 percent, cobalt by weight alloyed therewith and a sulfur content preferably less than 0.01 percent; a top layer of a conventional bright nickel electroplate preferably 0.15 to 1 mil thick and having from 0 to 50 percent, preferably about .1 to about 50 percent cobalt alloyed therewith and preferably from about 0.03 percent to about 0.3 percent sulfur by weight; and an intermediate layer 0.01 to 0.2 mil thick which comprises a deposit of nickel having from 0 to about 25 percent, preferably from .1 to 25 percent cobalt alloyed therewith and containing from about 0.25 percent manganese to about 4 percent manganese based on the total weight of said intermediate deposit. Sulfur in the intermediate layer is not necessary but can be present in quantity such as indicated for the lower layer. The term alloy is used herein to include codeposit and the term alloyed is used to include codeposited. Preferably the manganese concentration is kept in the range of from about 0.50 percent to about 2.5 percent. It is not necessary to have a cobalt content in the nickel but it can be used and commercial nickel often contains it up to 0.5 percent or thereabout. Cobalt may be regarded as the equivalent of nickel up to the above stated percentages for the purposes of this invention.

The mechanism by which the triple-layer coating system of the present invention acts to protect a corrodible substrate is more easily understood by referring to the accompanying drawing in which:

FIG. 1 illustrates schematically a triple-layer system with a corrosion pit which has not yet penetrated the in- I termediate layer.

FIG. 2 illustrates the same triple-layer system with the corrosion pit where the pit has reached and has attacked the intermediate layer.

FIG. 3 illustrates the same triple-layer system with the corrosion pit widened laterally but Where the lower layer has not been attacked substantially. These figures represent what is believed a typical modus operandi for corrosion pitting.

The composite electroplate of the present invention advantageously is employed over various substrates and particularly metal substrates susceptible to corrosion. Iron, steel, copper, brass, aluminum, zinc and magnesium with or without a copper deposit, are substrates protected by the composite electroplates of the present invention.

The manganese present in the intermediate layer of the instant triple-layer composites provides good corrosion protection to the substrate covered by the system. The electroplate composites of the present invention are more efiective than those using sulfur in the intermediate layer.

Corrodkote is the name given to an accelerated test in which a synthetic roadsoilslurry is applied to the plated surface of an article and the article is then exposed to a warm humid atmosphere. A Corrodkote slurry formulation includes both soluble and insoluble elements and sufficient liquid to give proper spreading consistency. The slurry is applied to the surface being. tested by means of av paint brush, or similar device, to produce a fairly uniform coating, after which the coated specimen is exposed to specified humidity conditions.

A standard Corrodkote. mixture, effective in testing chromium-nickel combinations over steel, is:

Kaolin grams 30 Ferric chloride "gram" 0.165 Cupric nirate do 0.035 Ammonium chloride do 1 Water ml 50 The CASS test involves exposing the plated parts to a salt spray containing small concentrations of cupric chloride and acetic acid.

Both the Corrodkote and the CASS tests have been accepted by the industry as well established accelerated tests for corrosion. For a complete description of the tests see Plating, vol. 44. P. 763, 1957.

In some instances neither the Corrodkote test nor the CASS test are absolutely reliable in predicting service life of plated parts on cars. Where some plated panels are rated good by the Corrodkote test, the same panels are less highly rated by the CASS test and the reverse would be observed with the other plated panels. Therefore the test results set forth hereinafter to show the advantages of the present invention are obtained by submitting the sample panels to 3 or 4 Corrodkote cycles, and instead of using more Corrodkote cycles, further submitting the panels to the CASS test. Controls or panels for comparison are always employed. A representative test would be 3 or 4 Corrodkote cycles plus 48 hours of CASS exposure.

The advantage of using the triple-layer composite systems to protect a corrodible substrate becomes significant when reference is made to FIGS. 1-3 of the drawing. These figures illustrate in sequence the progressive corrosion ofa three-layer composite according to the invention. As a corrosion pit is formed in the top nickel layer as shown in FIG. 1 (through a pore or other defect in the chromium decorative coat), the pit progressively enlarges hemispherically. This corrosion site continually enlarges until it reaches the more anodic intermediate layer.

In FIG. 2 the corrosion pit has attacked the intermediate layer, progressed until the pit has become substantially cylindrical rather than hemispherical and has undercut the intermediate layer slightly below the top layer of nickel. Because the lower layer is more noble than the two upper layers of nickel, the lower layer remains relatively free from corrosion.

In FIG. 3 there is shown a plate with the corrosion pit widened with the lower layer of nickel being attacked only very slightly. The rate of corrosion of the lower layer in relation to the intermediate layer is' very low.

In the triple-layer system the intermediate layer acts as the sacrificial anode primarily, while the top layer provides theb right surface for the decorative chromium; the composition of the intermediate layer need not be controlled as rigidly as the composition of the top layer in a duplex system.

As mentioned hereinbefore, the triple-layer system is most effective when the intermediate layer is anodic to the lower layer and the upper layer and wherein the lower layer is cathodic to the upper layer. The intermediate layer acts as a primary sacrificial anode and the upper layer acts as a secondary sacrificial anode, protecting the lower layer. The use of manganese as the alloying constituent with nickel in the preparation of the intermediate layer provides higher potentials than those in deposits prepared by the use of sulfur as the alloying constituent with nickel.

In order to carry the present invention into effect, the substrate is plated first with a lower layer of nickel and then with the intermediate layer of nickel and the upper layer of nickel. Any solution of nickel ions designed for electroplating nickel may be used.

The solutions should contain at least one of the following salts; nickel sulfate, nickel chloride, nickel fiuoroborate and nickel sulfamate, wherein the solution is adjusted to an operating concentration of nickel. Included among the various baths useful in carrying out the present invention are (l) the various barrel plating baths generally comprising nickel sulfate and nickel chloride as the source of the nickel ion and buffer systems comprising boric acid alone or in conjunction with magnesium sulfate or ammonium chloride, (2) the all-chloride bath designed for use where a high current density is desired, comprising nickel chloride as the source of nickel ion and boric acid' as the buffer, (3) the fiuoroborate bath comprising nickel fluoroborate as the source of nickel ion and free boric acid as the buffer alone or in combination with fluoroboric acid, (4) the common Watts-type bath designed for all purpose nickel plating and generally comprising nickel sulfate and nickel chloride as the source of nickel ion buffered with boric acid, (5) the all sulfamate bath comprising nickel sulfamate including boric acid as the buffer, (6) the chloride-sulfamate bath comprising nickel chloride and nickel sulfamate with boric acid as the buffer, and (7) other nickel baths made from nickel salts and complexing agents.

After the desired thickness is obtained for the first or lower layer of nickel, the manganese-containing intermediate layer of nickel is deposited. A manganese-supplying compound is added to one of the above named baths, the bath is adjusted to the appropriate concentration and a thin layer of manganese-containing nickel is deposited directly on the surface of the first or lower layer of nickel.

The composite is then completed by plating a third deposit of nickel directly on the surface of the intermediate plate. Normally this plate is fully bright to provide an optimum surface for the decorative chromium plate. The decorative chromium layer advantageously is from about 0.005 mil to about 0.2 mil thick. Each of the above layers of nickel may be deposited using more than one step such as, for example, by interrupting the plating cycle.

In its preferred form the composite coating of the present invention comprises a first or lower layer of duetile sulfur-free nickel. This preferred plate is deposited from a typical Watts-type or fluoroborate-type bath containing an effective amount of a sulfur-free leveler such as coumarin or the like. The top layer of nickel preferably being fully bright is deposited from one of the above baths using a brightener of the first class (sulfo-oxygen carrier) and a brightener of the second class. Where the top layer is high in sulfur content (0.1 to 0.3 percent) the lower layer also may be deposited from a bath containing in addition to a brightener of the first class (sulfo-oxygen compound) small amounts of a brightener of the second class. The baths disclosed in US. Patent 3,090,733 are useful for preparing the upper layers of nickel in the composite disclosed and claimed therein may be used to deposit the upper layers of nickel for the present invention.

As indicated hereinbefore, the lower and top layers of nickel may be deposited from baths of conventional compositions and in the baths there may be present one or more brighteners of the first class. These compounds generally comprise an aryl ring, a substituted aryl ring of an unsaturated aliphatic chain with a sulfur-containing radical in the form of s-ulfonic acids, sulfonates, sulfonamides, sulfimides, sulfinic acid and sulfones. The aryl ring advantageously may be derived from benzene, naphthalene and the like, the substituted aryl ring may be derived from toluene, xylene, naphthylamine, toluidine, benzyl naphthalene and the like and the alkylene chain may advantageously be derived from vinyl compounds or allyl compounds and the like. Examples of sulfo-oxygen compounds of the" above described type and which are useful particularly in the instant nickel plating baths are found in US. Patents 2,757,133 and 2,766,284.

Almost uniformly, the top layer of nickel is deposited from baths containing, in addition to brighteners of the first class, brighteners of the second class including organic compounds such as the various ketones, aldehydes, carboxylic acids, some proteins (gelatin) and the like; compounds such as the alkylenic carboxylic esters, the alkylenic aldehydes, the aromatic compounds such as the aryl aldehydes, the sulfonated aryl aldehydes, allyl and vinyl substituted compounds, coumarin and its derivatives, and the like; those compounds having acetylenic radicals (C C) including the acetylenic alcohols, nitrogen heterocyclics having an N-substituted acetylenic radical and the like; those compounds such as the azine, thiazine and oxazine dyes, the triphenyl methane dyes, the quinidines, pyrimidines, pyrazolcs and imidazoles, the pyridinium and quinolinium compounds, and the like; those compounds such as the nitriles, thionitriles and the like; and those compounds having the thioureide radical (N-C=S) such as the cyclic thioureides and thiourea.

Compounds considered useful as brighteners of the second class include the water-soluble acetylenic compounds set forth in US. Patent (Kard-os, et a1.) 2,712,522; the aryl, alkylene and arylalkynoxy sulfonic acids set forth in US. Patent 2,800,442; the alkylnoxy sulfonic and caiboxylic acids having the triple bond separated fromthe acid radical by at least one oxygen atom set forth in US. Patent 2,841,602; and the nitriles set forth in U. S. Patents 2,524,010, 2,647,866, 2,882,208, 2,978,391 and 3,093,557.

Where cobalt is desired as an alloying constituent in the nickel layers, the instant bath may be adjusted by adding any of the cobalt salts Well known to those skilled in the art. For example, the halides of cobalt are particularlymseful including cobalt chloride, cobalt bromide, and the like. Cobalt sulfate may be used also.

Nickel electroplating baths particularly useful in combination with these brightener systems include the Wattstype and fluoroborate-type baths having increased nickel content. Such baths are designed for use with organic brighteners in general; they may be operated at the higher current densities desirable for the effective use of the organic brighteners. The preferred Watts-type bath essentially comprises an overall nickel content ranging from 70'to 115 grams per liter provided by 270 grams per liter tdabout 450 grams per liter of nickel sulfate and from about 20 grams per liter to about 90 grams per liter of nickel chloride with about 30 to 40 grams per liter of boric acid as the buffer and the preferred fiuoroboratetype bath essentially comprises an over-all nickel content ranging from 75 to 110 grams per liter with about 30 grams per liter of boric acid as the buffer.

' For purposes of the present invention, boric acid is preferred as the bufferas an additive to maintain the desired pH. However, acetic acid, borax (sodium tetraborate), formic acid, the fluoroborates, and other compounds commonly known to have utility as buffers, may be used with the baths of the present invention with no apparent undesirable effects.

.Illustrative examples of wetting agents which may be employed in the baths for carrying out the present invention include a great number of the anionic surfactants. The sulfate type particularly may be used. Included among this type are certain of the akylsulfates, aralkylsulfates, alkylsulfonates, and aralkylsulfonates. I

The use of wetting agents in baths used in carrying out the present invention is desirable but optional; acceptable deposits are often obtained from baths having no wetting agent therein.

The preparation of the manganese-nickel plating baths advantageously is carried out by adding from about 0.25 gram per liter to about 200 grams per liter or more up to saturation, and preferably 1.0 gram per liter to 20 grams per liter of a manganese-supplying compound to any one of the above described baths used for depositing nickel. The optimum amount of the particular manganese-supplying compound necessary to impart an optimum amount of manganese in the nickel deposit varies with each compound; and, of course, the temperature of the bath and cathode current density vary the deposits. Moreover, many manganese-containing compounds which could be used to impart manganese into the nickel deposit are not very soluble in water and this limits the amounts which can be used.

Preferably, the operating temperature of a typical bath (Watts-type) is in the range of from about F. to about F. This range is not critical, however, and good deposits may be obtained at temperatures as low as 50 F. or as high as F. or even at the boiling point of the electrolyte. When the Watts-type bath is employed, current densities ranging from about 10 to 50 amperes per square foot are preferred. The pH should be in the range of from 1.5 to 5.5 and preferably in the range of from 4 to 5.

Trivalent manganese salts (MnCl etc.) hyldrolyze in contact with water to form manganous Mn++ ions. Thus, while manganic salts could be added to the plating bath, they would serve only as a source of Mn ions, and we prefer to add the Mn++ ions directly as a manganous salt.

Manganates, manganic acid, permanganates and permanganic acid, or other compounds containing manganese in a higher valence state than two (as present in manganous salts) may be added to the plating bath, provided the compounds are reduced by action of reducing agents or reducing agents or hydrogen liberated in the bath to produce manganous Mn++ ions.

Compounds such as manganese sulfate, either manganous sulfate or, less desirably, manganic sulfate; manganese chloride, either manganous chloride or, less desirably, manganic chloride; manganese carbonate, manganous carbonate or, less desirably manganic carbonate; manganese hydroxide, either manganous hydroxide or, less desirably, manganic hydroxide; manganese acetate, manganese borate, manganese formate, manganese propionate, may be used. Other such compounds yielding the Mn++ ion in solution are manganese bromide, manganese fluoride, manganese iodide, manganese ammonium arsenate, manganese benzoate, manganese hypophosphite, and manganese selenate. Other compounds useful in forming the intermediate layer are the manganese salts of the aryl sulfonates, aryl sulfonamides and arylsulfimides, including the manganese salts of any of the various sulfo-oxygen compounds common in the art of electroplating.

As a further feature of the present invention a sulfooxygen compound or brightener of the first class is added to the manganese-containingbath in small amounts. The manganese may be present in any form which will provide Mn++ ions. The sulfo-oxygen compound acts to provide a semi-bright deposit of enhanced lustre. The concentrations of the sulfo-oxygen carrier useful in forming the deposits are from about 0.5 gram per liter to about 2 grams per liter of the sulfo-oxygen compound, but amounts outside this range are useful also. -It has been found that relatively small amounts of sulfur are imparted into the deposit by these compounds, an amount which is much less than is obtained in the deposit from a fully bright nickel bath containing a brightener of the second class.

The following Table A sets forth specific compositions of baths useful for depositing the lower layer in preparing the triple-layer composite electroplate of the present invention:

showed that the coatings according 'to this Example I of this invention developed only a few rust spots (less than TABLE A Borie Bath Nickel Salts, g./l. Addition Agent, g./l. Other Additives, g./. Wetting Agents, g./l. BAtgd pH u or g./l.

1o. NlSO4.6HzO, 300; Sodium lauryl sulfate, 0.02-- 37 3. 5

NiClz.6Hz0, 37. 2a Ni gtgnmo, 300; Coumnrin, 0.2 Formaldehyde (40%), 0.1 ce./l.. do 37 4.0

i 12.6112 37. 3a NlSOmfiHgO 300; Nickel Formate, 4.5 Formaldehyde, 0.5 cc./l. 30 2. 5

NlClfllfiI'IiO, 45; COSO4.6H90, 30. NlSO4.6H2O, 150; 3 Bromocoumarin, 0.2"- 3O 4.

NlC1g.6HzO, 15 NiSO .6H1O, 300; Butynediol, 0.1 Chloral, 0.05 30 4. 0

NlCl'fiHgO, 30. NlSO .GEl5O, 300; Coumarin, 0.1 Formaldehyde 0.1 cc./l.; Sodium oetyl sulfate, .1 35 4. 0

NiChfiHzO, 30. Saceharin, 1.0. Ni(BF 300; NiClz.6I-Iz0, Coumarin, 0.2 Chlorul, 0.05 .do 3.5

The following table B sets forth specific compositions of baths useful for depositing an upper layer or top layer in preparing the triple-layer composite electroplate of the present invention:

ten) whereas deposits using the same type top and bottom layers (same total thickness) of nickel Without the intermediate layer developed from 38 to above a hundred rust spots per panel.

TABLE B Borio Ex. No. Nickel Salts, g./l. Organic Suite-oxygen epd., g./l. Brighteners, g./l. Wetting Agents, g./l. Bmtzfid pH u or g./l.

1b NiSOi.6Hz0(,)300; Naphthalenedisulionic acid, 4. Reduced fuchsin, .007-.." Sodium lauryl sulfate, 0.03 37 3. 5

NlCl2.6H 37. 2b NiSO4.6HzO, 300; Saccharin, 1; Allyl sulionate Butynediql, 0.2; do 37 4, 0

NlCh.6HgO, 37. 0.5. C0umar1n, 0.1. 3b NiSO4.6HgO, 300; Dibenzenesulfonimide, 3 Allylpyridnnurn do 37 4, 0

NiClmHzO, 37. br0n1l1e, 0.0o. NiSO4.6H O, 300; p,p xoy-bis(dibenzenesulion- B,B thiodipropionitrile, Sodium octyl sulfate, 0.1 27 4.0

NlClz.GHzO, 37. amide), 3. 0.003. NlSO4.6HzO, 150; Saceharin, 2, Allyl sulionate, 1.. ...d0 do..- 37 3,5

Nionemo, 150. 6b Ni[(NH )SO ]z, 400; Same as 2b Same 08 2b... Same as 1b 37 4.0

NiClzfiHzO, 15. 7b NiSO .6H O, 300', Benzenesullonaimdc, 2 Same as its 37 3.5

NiCl2.6H2O. 40.

Example 11 Following are examples of tests of the invention:

A Example 1 Using bath 2:: from Table A, a 0.5 mil layer of nickel was deposited on steel panels. The coated panel was rinsed with water and a 0.1 mil layer of nickel was deposited from the next following bath at a cathode current density of 20 a.s.f. The bath was kept at a temperature of about 140 F. and a pH of about 5.0.

Constituents: Grams per liter NiSO .6H 0 300 Nichol-I 0 Boric acid (B 130 45 MnSO .4H O 46 (NHQ SQ, 20

Water to make 1000 ml.

This example varies from Example I mainly in that the manganous sulfate concentration is reduced from 46 to 10 g./1.

Constituents: Grams per liter NiSo .6H O 300 NiCl .6H O 45 Boric acid 45 MnSO .4H O 10 (NH )2SO 20 Temperature 140 F. pH 5.0 CD, a 5.1 20

Water to make 1000 cc.

The manganese containing deposit contained about 0.5% manganese as against about 0.8% in Example I.

Example III Example IV Varying the cathode current density, it was found that at a current density of a.s.f. the potential of the inter mediate deposit (measured in millivolts against a saturated calomel electrode in sodium chloride solution pH 3.0, adjusted with acetic acid) is more electronegative than the two-layer deposit described in Example III, which two layer deposit has a potential of about 350 mv. versus a saturated calomel electrode.

Example V At 5 a.s.f. the potential of the deposit is more electronegative than that of the two-layer deposit described in Example III (-350 mv.).

Example VI At a.s.f. the potential of the deposit is about -400 to 500 mv. depending upon concentration of the MnSO, in the solution.

Example VII At a.s.f. the potential of the deposit is about 500 to -560 mv. depending upon the MnSO concentration in the solution.

Example VIII At 80 a.s.f. the potential of the deposit is about 500 to 560 mv., varying but little with the concentration of the solution in respect to MnSO At 20 g./l. and higher concentrations of M1150 the potential changes but little.

Use of ammonium sulfate in the plating solution from which the intermediate layer is deposited is desirable but optional and limits are not highly critical. The ammonium sulfate addition aids in preventing burning at the edges of the panels. With increasing manganese sulfate concentration in the bath (above about 40 g./l.) increasing the ammonium sulfate concentration up to about 35 g./l. may be very helpful.

The present invention also includes composites or laminates of nickel having more than three layers of nickel and composites or laminates wherein the manganese-nickel layer is sandwiched between layers of nickel which will have relative potentials equal substantially to each other and more cathodic than the intermediate layer.

Examples of composites according to the present invention include composites in addition of those already described, including in addition to the intermediate, manganese-containing layer, (1) a sulfur-free lower layer and a sulfur-free upper layer, (2) a bright lower layer and a bright upper layer and (3) a sulfur-containing lower layer and a sulfur-containing upper layer. The lower layer may contain from 0 to about 0.15 percent sulfur and the upper layer may contain from 0 to about 0.4 percent sulfur. Higher amounts of sulfur can be obtained in the nickel deposits but there is no advantage in using amounts of sulfur above about 1.0%.

While specific examples of the invention have been set forth hereinabove, it is not intended that the invention be limited solely thereto, but to include all of the variations and modifications falling within the scope of the appended claims.

What is claimed is:

1. A firmly bonded laminated corrosion-protective composite coating on a metal base susceptible to atmospheric corrosion comprising as its essential layers three adjacently bonded layers of electrodeposits, the lower layer of which consists essentially of an electroplate selected from the group consisting of nickel electroplate and nickel-cobalt alloy electroplate containing at least about nickel, the intermediate layer of which is a manganese-containing electroplate selected from the group consisting of nickel electroplate and nickel-cobalt alloy electroplate containing at least about 75% nickel, said manganese being present in said intermediate layer in suflicient quantity to render said intermediate layer anodic to its adjacent, layers, and the upper layer of which consists essentially of an electroplate selected from the group consisting of nickel electroplate and nickel- 10 cobalt electroplate containing at least about 50% nickel.

2. A coating in accordance with claim 1 wherein said intermediate layer contains about 0.25 to about 4% by weight manganese.

3. A coating in accordance with claim 1 wherein said lower layer has a thickness of about 0.3 mil to about 2 mils, said intermediate layer has a thickness of about 0.01 mil to about 0.2 mil, and the upper layer has a thickness of about 0.15 mil to about 1 mil.

4. A coating in accordance with claim 3 wherein said intermediate layer contains about 0.25% to about 4% manganese.

5. A coating in accordance with claim 1 wherein said intermediate layer contains about 0.5% to about 2.5% manganese.

6. A coating in accordance with claim 3 wherein said intermediate layer contains about 0.5% to about 2.5% manganese.

7. A coating in accordance with claim 2 wherein said upper layer is electroplated with a chromium deposit having a thickness ranging from about 0.005 to about 0.2 mil, and said lower layer being bonded to a substrate of the group consisting of iron, steel, copper, zinc, aluminum, magnesium and alloys thereof.

8. A method of making a triple layered, laminated coating on a metal substrate comprising electrolyzing between said substrate and an anode a solution comprising, in addition to water, nickel sulfate and nickel chloride, to form a first layer of nickel on said substrate; electrolyzing between said first coating and an anode a solution comprising, in addition to water, nickel sulfate, nickel chloride and a soluble manganese compound, to form a second layer of nickel containing manganese, said manganese being present in said intermediate layer in suflicient quantity to render said intermediate layer anodic to its adjacent layers; and electrolyzing between said second layer of nickel and an anode a solution comprising, in addition to water, nickel sulfate, nickel chloride and a soluble sulfur compound to form a third layer of nickel on said second layer.

9. The invention as defined in claim 8 wherein the intermediate layer is deposited from a solution containing ammonium sulfate.

10. A method of making a triple layered, laminated coating on a metal substrate comprising electrolyzing between said substrate and an anode an aqueous solution comprising nickel sulfate, nickel chloride and a buffer compound to form the first of said layers on said substrate; electrolyzing between said first layer so deposited and an anode a solution comprising nickel sulfate, nickel chloride, a manganous compound and a buffer to form said second nickel layer containing manganese, said manganese being present in said intermediate layer in suflicient quantity to render said intermediate layer anodic to its adjacent layers; and electrolyzing between said second layer and an anode a solution comprising nickel sulfate, nickel chloride, a buffer and a soluble sulfur compound to form said third layer of nickel.

11. A method of making a triple layered, laminated coating on a metal substrate comprising electrolyzing between said substrate and an anode a solution containing nickel to form on said substrate a first nickel layer substantially free of sulfur; electrolyzing between said first nickel layer and an anode a solution containing nickel ions and manganese ions to form on said first layer an intermediate nickel layer containing manganese; and electrolyzing between said intermediate layer and an anode a substantially sulfur-free solution containing nickel to form a third and substantially sulfur-free nickel coating.

References Cited UNITED STATES PATENTS 3,090,733 5/1963 Brown 29-194 X HYLAND BIZOT, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,355,268 November 28, 1967 Arthur H. Du Rose et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Columns 7 and 8, TABLE B, sixth column, line 4 thereof, for "27" read 37 Signed and sealed this 7th day of January 1969.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

Claims (1)

1. A FIRMLY BONDED LAMINATED CORROSION-PROTECTIVE COMPOSITE COATING ON A METAL BASE SUSCEPTIBLE TO ATMOSPHERIC CORROSION COMPRISING AS ITS ESSENTIAL LAYERS THREE ADJACENTLY BONDED LAYERS OF ELECTRODEPOSITS, THE LOWER LAYER OF WHICH CONSISTS ESSENTIALLY OF AN ELECTROPLATE SELECTED FROM THE GROUP CONSISTING OF NICKEL ELECTROPLATE AND NICKEL-COBALT ALLOY ELECTROPLATE CONTAINING AT LEAST ABOUT 50% NICKEL, THE INTERMEDIATE LAYER OF WHICH IS A MANGANESE-CONTAINING ELECTROPLATE SELECTED FROM THE GROUP CONSISTING OF NICKEL ELECTROPLATE AND NICKEL-COBALT ALLOY ELECTROPLATE CONTAINING AT LEAST ABOUT 75% NICKEL, SAID MANGANESE BEING PRESENT IN SAID INTERMEDIATE LAYER IN SUFFICIENT QUANTITY TO RENDER SAID INTERMEDIATE LAYER ANODIC TO ITS ADJACENT LAYERS, AND THE UPPER LAYER OF WHICH CONSISTS ESSENTIALLY OF AN ELECTROPLATE SELECTED FROM THE GROUP CONSISTING OF NICKEL ELECTROPLATE AND NICKELCOBALT ELECTROPLATE CONTAINING AT LEAST ABOUT 50% NICKEL.

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