JP2008019472A - Metal surface treatment method and metal surface treated body obtained by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inexpensive rust preventive machine parts without causing rust on the surface of steel. <P>SOLUTION: In the metal surface treatment method, a metal layer having an ionization tendency higher than that of iron is formed on the surface of steel, and the metal surface is provided with a treatment layer comprising a titanium phosphate based compound expressed by Ti(OH)<SB>x</SB>(PO<SB>4</SB>)<SB>y</SB>(HPO<SB>4</SB>)<SB>z</SB>(H<SB>2</SB>PO<SB>4</SB>)<SB>l</SB>(OR)<SB>m</SB>(R is a 1 to 4C alkyl group, and x, y, z, l and m are integers) or a condensation product thereof as effective components. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rust preventive property on a metal surface, a treatment for forming a rust preventive film free of hexavalent chromium on zinc and zinc alloy plating, and a method for forming a trivalent chromate film.

  Conventionally, as a rust preventive treatment for the steel surface, chromate treatment is generally performed on electrodeposited cations or electrogalvanized. However, the conventional surface treatment has a problem that it contains lead and hexavalent chromium which are environmentally hazardous substances. The use of lead and hexavalent chromium as a carcinogenic substance is regulated, and the use of ELV directive has been prohibited since July 2007.

  The above-mentioned rust prevention technology forms a film made of zinc or a zinc alloy, and further forms a chromate film harmful to the environment on the surface of the above film, thereby elution of zinc by a hexavalent chromium compound by its sacrificial anticorrosive action. It is a technology to prevent.

  In addition, mechanical parts using a plating process such as nickel plating or a stainless steel plate such as SUS440C or SUS630 as a noble metal from steel are known.

  However, the mechanical parts using the above stainless steel and non-ferrous materials have a problem in terms of cost, and the use places are limited. In contrast, mechanical parts that have been plated such as nickel plating do not have cost problems, but the bearings that have been subjected to the above nickel plating process tend to have pinholes in the nickel plating. Corrosion tends to occur from the part.

  On the other hand, the surface treatment by electrolytic treatment tends to occlude hydrogen in the steel member and causes problems such as delayed fracture such as delayed fracture. Furthermore, rust prevention treatment and cation coating with galvanized steel surface, when lead and hexavalent chromium, which are environmentally hazardous substances, are removed, rust is likely to occur and the function of machine parts is hindered.

  Therefore, an object of the present invention is to provide an inexpensive rust-proof mechanical component that does not generate rust on the steel surface.

The present invention, on the steel surface to form a large metal layer ionization tendency than _{iron, Ti (OH) x (PO} 4) on the metal surface _{y (HPO 4) z (H} 2 PO 4) l (OR) m ( R is an alkyl group having 1 to 4 carbon atoms, and x, y, z, l and m are integers). A metal having a treatment layer containing a titanium phosphate compound represented by the compound or a condensate thereof as an active ingredient The surface treatment method can solve the above problems.

In order to raise the level of rust prevention, the Ti (OH) _x (PO ₄ ) _y (HPO ₄ ) _z (H ₂ PO ₄ ) _l (OR) _m (R is an alkyl group having 1 to 4 carbon atoms, x It is effective to form the treatment layer containing, as an active ingredient, a titanium phosphate compound represented by the following formula: y, z, l, and m, together with a layer made of chromium oxide.

In particular, a layer of chromium _{oxide, Ti (OH) x (PO} 4) on the metal surface _{y (HPO 4) z (H} 2 PO 4) l (OR) titanium phosphate based compound represented by the _m Alternatively, it is effective to provide the treatment layer containing the condensate as an active ingredient.

  The titanium phosphate compound may comprise a compound obtained by reacting titanium tetrachloride with water, an alcohol having 1 to 4 carbon atoms, or a mixed solution thereof, and further reacting with phosphoric acid. Is possible.

  These are water-soluble liquids that can be coated and dried on the metal surface or chromium oxide surface, which has a higher ionization tendency than iron, and can be coated with a coating on the surface by dissolving in a water-soluble polymer. It can also be formed.

  A metal surface having a higher ionization tendency than iron can be produced by plating zinc or vanadium.

  Furthermore, this invention can provide the metal surface treatment body obtained by the method mentioned above.

  According to this invention, the chromium oxide compound (III) can be formed on the galvanizing without containing hexavalent chromium which is a carcinogenic substance, and the rust preventive power of the pulley can be achieved by the passivating effect of titania phosphate. Can be maintained.

  In a preferred embodiment of the present invention, the method of forming a layer made of chromium oxide on the surface of the galvanized metal layer having a higher ionization tendency than iron does not contain hexavalent chromium unlike conventional chromate, Only trivalent chromium oxide is used.

A conventional chromate film is formed by the following reaction.
Zn + 2H → Zn ²⁺ + H ₂ (1)
2Cr ⁶⁺ + 2Zn + H ₂ → 2Cr ³⁺ + 2Zn ₂ ++ 2H ⁺ (2)
Cr ³⁺ +3 (OH) ⁻ ⇔Cr (OH) ₃ (Cr ⁶⁺ eutectoid: hazardous substance) (3)

In addition, since the formation of the trivalent chromium oxide does not include hexavalent chromium ions, only the following reactions (4) and (5) occur.
Zn + 2H → Zn ²⁺ + H ₂ (4)
Cr ³⁺ +3 (OH) ⁻ ⇔Cr (OH) ₃ ... (5)
Chromium hydroxide generates mono-, di-, and tri-hydroxides depending on the number of waters provided from the nature of the ions, so Cr (OH) ₃ is a hydrated oxide structure, so It becomes a hydroxide structure.
[Cr (H ₂ O) ₅ OH] ^{3 +} · + 1H ⁺
[Cr (H ₂ O) ₄ OH] ³ ++ 2H ⁺
[Cr (H ₂ O) ₃ OH] ³⁺ + 3H ⁺

  On the other hand, by applying or spraying the titania phosphate compound solution and bringing the oxygen and water in the air into contact with the surface of the dried object skin, a surface reaction occurs and trivalent ozone and divalent oxygen are generated. .

This oxygen is unstable and undergoes a redox reaction between trivalent and divalent. O ^- ₂ produced by the reduction of oxygen is added to the oxidation reaction intermediate to form a peroxide, and through hydrogen peroxide, it becomes a hydroxyl radical (.OH) that has a stronger oxidizing power. Strong effect to passivate.

The hydroxyl group-OH of these hydroxides is crosslinked to form a dimer or trimer. If silica colloid is present here, the effect of accelerating the crosslinking is expected due to the high production rate of Cr (OH) ₃ .

(Function)
According to the present invention, the zinc anticorrosion technology, which is a chromate replacement process using harmful hexavalent chromium, has no influence on the environment because hexavalent chromium is not used.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
The mechanical component which is the object of the method according to the present invention is a power steering pump, idler, water pump, air conditioner, alternator, or auto tensioner bearing which applies tension to the belt connecting them, which operates with the driving force of the engine shown in FIG. A pulley that fits into the case was taken as an example.

  An example of pulley engagement is shown in FIG. The pulley 1 is fixed to the bracket 8 with a shaft 4 and a nut 3 by fitting a bearing 2. In fixing, the collar 5 and the dust cover 6 are simultaneously fixed to the bracket 8 by the shaft 4 and the nut 3. The bracket 8 is fixed to a fitting portion in the engine room by a bolt 7 and forms a mechanical element capable of transmitting engine driving force by a belt in the arrangement shown in FIG.

  A film layer 9 was formed on the surface 11 of the pulley 1. The coating layer 9 is formed on the entire surface of the pulley-1. This has the purpose of preventing rust of the pulley 1 and preventing the bearing 2 from generating rust. Although pulley 1 which fits a bearing was shown as an embodiment, it is not limited to these in particular.

  The surface 11 of the pulley 1 may be either a steel surface press-formed from a steel plate, or a steel surface that has been ground or polished.

  Further, as shown in FIG. 3, the steel surface may be configured by forming a zinc coating 12 on the surface of the pulley base material 11 and forming a chromium oxide layer 13 on the surface of the coating 12. It doesn't matter.

  When the zinc coating 12 is applied, it is a coating made of zinc or a zinc alloy, and examples of the zinc alloy include tin-zinc, iron-zinc, nickel-zinc and the like. As a method for forming the film, a method by plating is preferable.

  In the method of galvanizing the pulley base material 11, first, the pulley is supported by a conductive rack, and pretreatment such as water washing, pickling, degreasing and the like is performed. Then, using a zinc metal plate for the anode, the pulley base material 11 is immersed in a plating bath in which a predetermined amount of zinc cyanide, sodium cyanide, sodium hydroxide, and zinc oxide is dissolved, and connected to the cathode. Next, galvanization is performed by passing electricity. After galvanization, the electrode is removed and immersed in 1% nitric acid solution to activate the galvanized surface.

  By spraying titania phosphate onto the steel surface or zinc or zinc alloy film surface by the above-mentioned manufacturing method, the surface reaction occurs when oxygen and water in the air contact the fully cured object skin surface. Produces monovalent ozone and divalent oxygen. This oxygen is unstable and undergoes a redox reaction between trivalent and divalent. A peroxide is formed by adding to an oxidation reaction intermediate produced by reduction of oxygen, and a hydrogenated radical is converted into a stronger hydroxyl radical (.OH) to form a passivated layer on the surface. This passivating layer has a uniform film thickness of 1 μm or less.

Examples of the titanium phosphate compound include Ti (OH) (H ₂ PO ₄ ) ₂ (OR), Ti (OH) (PO ₄ ), Ti (OH) ₂ (H ₂ PO ₄ ) (OR), Ti (OH) (HPO ₄ ) (OR), Ti (OH) (HPO ₄ ) (H ₂ PO ₄ ), Ti (OH) ₂ (H ₂ PO ₄ ) ₂ , Ti (OH) ₃ (H ₂ PO ₄ ), Ti (OH) ₃ (OR), and the like.

  Although the present invention has been described based on the preferred embodiment, it goes without saying that other modifications can be appropriately made without departing from the gist of the present invention.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not restrict | limited by these Examples.

  The pulley base material 11 (steel) was hung on a rack, and washed with water, pickled, and degreased. The pulley base material 11 subjected to the above treatment was immersed in a zincate galvanizing bath to form a galvanized layer 12 through electricity. FIG. 3 shows a configuration diagram of the processing layer.

An aqueous solution of titania phosphate was prepared by the following procedure, and the passivation layer 14 was formed by dipping treatment.
Ti (OH) _x (PO ₄ ) _y (HPO ₄ ) _z (H ₂ PO ₄ ) _l (OR) _m (R is an alkyl group having 1 to 4 carbon atoms, x, y, z, l and m are integers) Soaked in an aqueous solution containing The aqueous solution can be prepared by the following method. For example, titanium tetrachloride was reacted with alcohol. An alternative to alcohol may be water. The composition is not particularly limited, but may be any of water and alcohol, or a mixed aqueous solution thereof.

  The amount of titanium tetrachloride added was 15 vol%, and the reaction temperature was 25 ° C. The addition amount of titanium tetrachloride may be 10 to 30% by volume, and the reaction temperature only needs to keep the solution liquid.

  The pH of the produced aqueous solution is acidic and 5 or less. The phosphoric acid was added to these and the said titanium phosphate type compound 14 was produced.

  The reaction solution was diluted 20 times with a solvent such as water or alcohol. If it is less than 10 times, even if a small amount of phosphoric acid is added, it tends to become cloudy. The cloudy liquid has a high activity effect such as antibacterial, but the product to be used is discolored or white powder appears on the surface, but there is no problem in forming the passivating layer.

  The addition amount of phosphoric acid may be 8 to 500 parts by volume with respect to 100 parts of the reaction solution, and may be in an acidic state.

  The present invention can be applied by a method of immersing the target product.

  In this way, the pulley shown in FIG. 3 was manufactured. The thickness of the coating layer 9 was about 5 to 13 μm for the zinc coating (12) and about 0.7 μm for the reaction layer (14) of titania phosphate.

As shown in FIG. 4, the pulley base material 11 is formed in the same manner as in Example 1 with the galvanized layer 12 and the yellowish white chromium oxide (III) layer 13 by the galvanizing method as in Example 1. A pulley was made. The thickness of the coating layer 9 is the same as in Example 1. The zinc plating bath at this time is a zincate, a salt bath, and a cyan bath. ZT-44
Three types were formed with 1SR.

The pulley was immersed in the reaction solution containing the above-described _{Ti (OH) x (PO 4} ) y (HPO 4) z (H 2 PO 4) l (OR) m. After soaking, it was taken out in the air and dried at 70 ° C. for 30 minutes to form a titania phosphate compound layer 14.

In the present invention, effective reagents for forming a layer made of chromium oxide include those shown below.
EBARA Eugleite Co., Ltd .: Trivalent process 100, 200, 300, 400, 500
Dipsol Co., Ltd .: ZT-441SR, 444Y, 444A, B, C (3 liquid type)
Nippon Surface Science Co., Ltd .: Triner Process TR-173, 174, 175, 170
YUKEN INDUSTRY Co., Ltd .: Metas Process YFE, YFA
Murata Co., Ltd. (SurTec Co.): chroming method SurTec 680 555 555S as required
Canning Japan Co., Ltd .: Tripas ELV Blue, Tripas Ultra Blue, Tripas Blue, Tripas XL, Chromac ELV
Okuno Pharmaceutical Industry Co., Ltd .: ES Coat 606, ES Coat 701, ES Coat, ES Coat 30, ES Coat Black Atotech Japan Co., Ltd .: Eco Tri, Eco Tri Blue Ultra, Meltex Co., Ltd. UNIQLO 920, Power Coat 903, Power Coat 903Y, Power Coat 910 manufactured by Taiho Corporation
Mihara Sangyo Co., Ltd. Raster-M-200, Raster-M-100, Raster-MY-200, Raster-M-300, Raster-M-400

  The corrosion resistance test was evaluated based on the presence or absence of rust generated on the outer peripheral surface of the pulley in a salt spray test according to JIS Z 2371 by fitting the bearing to the pulley. The test time at this time is 36 hours and 96 hours.

Further, as Comparative Example 1, a pulley having only a sacrificial anticorrosive surface on which a film made of zinc or a zinc alloy was formed on the surface of the pulley and a hexavalent chromium-containing chromate film formed on the surface of the film were prepared. This surface contains 40 mg / m ² or more of harmful hexavalent chromium.

  Table 1 shows the effect of each example.

  In Comparative Example 1 in which the zinc as a specimen was electrogalvanized from zincate, cyan, and salt plating baths, white zinc oxide was generated on the entire surface 36 hours after the start of spraying salt water.

  On the other hand, in the specimen in which the surface layer of electrogalvanizing shown in Example 1 was immersed in an aqueous titania phosphate solution, white rust of zinc oxide did not occur even after 36 hours from the start of salt spraying.

  Furthermore, as shown in Example 2, a white rust of zinc oxide was applied to a test piece in which a commercially available trivalent chromium oxide was applied to the surface layer of electrogalvanized as a rust prevention treatment and phosphoric titania was formed on the resurface. Did not occur.

In the pulley which is a specimen of Comparative Example 2 containing 40 mg / m ² or more of harmful hexavalent chromium, no zinc oxide was observed after 36 hours, but white zinc was observed over the entire surface after 96 hours. Oxide was generated.

  This invention can form chromium oxide compound (III) on zinc plating without containing hexavalent chromium which is a carcinogenic substance, and maintains the antirust ability of pulleys by the passivating effect of titania phosphate. It has industrial applicability in that it can be used.

The use figure of the drive transmission pulley as a machine component used as the object of the method according to the present invention. FIG. 3 is a cross-sectional view of a configuration of a pulley as a machine part that is a target of the method according to the present invention. The outline sectional view of the metal surface treatment object containing the galvanization layer and phosphate titania compound layer concerning the present invention. The outline sectional view of the metal surface treatment object containing a galvanization layer, a chromium oxide layer, and a phosphoric acid titania compound layer concerning the present invention.

Claims (4)

The steel surface to form a large metal layer ionization tendency than _{iron, Ti (OH) x (PO} 4) on the metal surface _{y (HPO 4) z (H} 2 PO 4) l (OR) m (R is the number of carbon atoms A metal surface treatment method comprising providing a treatment layer containing a titanium phosphate compound represented by 1 to 4 alkyl groups, x, y, z, l and m as integers) or a condensate thereof as an active ingredient. Ti (OH) _x (PO ₄ ) _y (HPO ₄ ) _z (H ₂ PO ₄ ) _l (OR) _m (R is an alkyl group having 1 to 4 carbon atoms, x, y, z, l and m are integers. 2. The metal surface treatment method according to claim 1, wherein the treatment layer containing a titanium phosphate compound represented by (2) or a condensate thereof as an active ingredient is formed together with a layer made of chromium oxide.   The titanium phosphate compound comprises, as an active ingredient, a compound obtained by reacting titanium tetrachloride with water, an alcohol having 1 to 4 carbon atoms, or a mixed solution thereof, and further reacting with phosphoric acid. Item 3. The metal surface treatment method according to Item 1 or 2.   The metal surface treatment body obtained by the method in any one of Claims 1-3.

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