JPS6137972A - Method for covering aluminum clad material with dissimilar metal - Google Patents

Abstract

PURPOSE:To cover simply an aluminum clad material with a dissimilar metal, by forming a chemically formed film on Al surface of the clad material treated with high temp. demineralized water, electroless plating the surface other than Al surface, then bringing the Al surface into contact with halogenized metal, and heating said material. CONSTITUTION:The Al clad material W composed of one side of Al or Al alloy 2 and the other side of an iron 1 is dipped in >=80 deg.C demineralized water or aqueous soln. 3 for about 3-10min, to form the chemically formed film 4 made of dense boehmite. Next, the treated material W is dipped in an electroless Ni plating liquid 5, to form a Ni plated layer 6 on the iron 1 surfasce using said film 4 as masking. Thereafter, halogenized metal powder such as CuCl is adhered to the Al 2 surface through binder such as vaseline, and said material is heated to temp. in which a substitution reaction between Al and halogenized metal is caused. In this way, the film 4 is removed, and the Al 2 surface is coated with a metallic layer 7 such as Cu reduced and precipitated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of coating an aluminum-based cladding material with a dissimilar metal.

[Conventional technology]

For plating when element +4 is iron, copper, etc., use solvent cleaning 1.
．． Plating is performed after alkaline degreasing, water washing, pickling and water washing. On the other hand, the pre-plating treatment for aluminum is extremely complicated, and after degreasing,? It is generally connected to JU-sleeves, water washing, nitrofluoric acid etching, water washing, zinc replacement, water washing or nitric acid washing, water washing, and zinc replacement.

As described above, plating aluminum requires special pretreatment, and it is extremely difficult to plate both sides of an aluminum clad material such as aluminum and copper or copper alloy in the same process. Furthermore, plating on aluminum has problems in terms of adhesion of the coating metal.

On the other hand, as a method of coating a metal with a different metal, for example, copper chloride is brought into contact with the surface of an aluminum base material, and reduced to copper chloride by heating to form an interdiffusion layer of aluminum and a copper coating layer on the surface of the aluminum base material. A method for obtaining it is known, and its contents are well summarized in Japanese Patent Publication No. 58-7786. Such a diffusion coating process was invented because aluminum is a metal that is difficult to process with ordinary plating, as mentioned above.

In order to coat an aluminum-based cladding material with a different metal, diffusion coating is suitable for the aluminum surface, and plating is suitable for the non-aluminum surface.

Therefore, when each side of an aluminum cladding material is treated using a separate method, for example, when each side is treated with a different treatment method, or when the treatment method is the same but coated with different metals, the most important thing is masking technology. be.

or when applying only to the aluminum surface of an aluminum cladding material, apply masking tape to the non-treated side as disclosed in Japanese Patent Publication No. 58-42266, or weld two sheets as described in the same publication. Law and Special Public Service 1977-
As disclosed in Japanese Patent No. 8161, a method is known in which a binder such as vaseline is applied to the surface to be treated.

By repeating the two-piece welding process twice, it is easy to diffuse coat the aluminum side of the aluminum clad material and apply normal plating to the other side, but if the product requires complex forming, two Sheet welding method cannot be used. In other words, the two-piece welding method is effective when the product is made by simple processing such as pressing after coating with dissimilar metals, but if forming processing must be performed before coating with dissimilar metals, the welding process itself is effective. becomes impossible. Furthermore, in the two-piece welding method, it is not possible to treat the end faces of the cladding material.

On the other hand, the tape masking method requires that the aluminum cladding material be in a shape that allows the tape to be applied, and that the tape itself must be able to withstand high temperatures of 400 to 500°C. Even if a masking agent with excellent heat resistance and resistance to halides were developed, there would always be problems such as how to apply the masking agent and how to remove it after processing.
The aluminum side of the aluminum cladding material
When processed according to Publication No. 3-8161, when the copper chloride is in a molten state, the copper chloride wraps around the other surface, that is, the non-aluminum surface, and unless the material of the other surface is a material that can withstand halides, the other surface will be severely damaged. It will corrode. Furthermore, the aluminum halide gas generated during the reaction also contributes to corrosion of other surfaces.

In fact, it is difficult to coat aluminum-based cladding materials with dissimilar metals without employing complicated processes, and only when the metal that makes up the slightly non-aluminum surface has excellent resistance to halides. The method of diffusion coating the aluminum surface and then plating the entire surface according to Japanese Patent No. 43-8161 is the only method for coating the clad material with a different metal.

Medium [FJM-3 for Solving Problems The present inventor has invented a method of masking an aluminum-based cladding material by electroless plating in order to eliminate the drawbacks of the above-mentioned conventional methods.

That is, after applying a chemical conversion treatment to the aluminum-based cladding material, which is conventionally performed for the purpose of improving the corrosion resistance of aluminum,
When electroless nickel plating is applied, normal plating is obtained on the non-aluminum surface of the cladding material, but no nickel adheres to the aluminum surface. Furthermore, after applying copper chloride to the aluminum surface via a binder and heating it to 400-500"c, an aluminum-copper interdiffusion layer and a copper coating layer were obtained on the aluminum surface. At this time, the non-aluminum surface Since it is coated with corrosion-resistant nickel, it is completely unaffected by reactive gases and is not corroded by molten copper chloride.

The present invention is based on such research results, and its gist is that the first step is to immerse an aluminum-based cladding material in pure water or an aqueous solution at 80°C or higher to form a chemical conversion film on the aluminum surface. , Using the chemical conversion film as a mask, ``The second step is electroless plating on the non-aluminum surface, and the metal halide is brought into contact with the aluminum surface, heated to a temperature higher than the temperature at which a substitution reaction occurs between the metal halide and aluminum, and the aluminum surface is coated. The third step is to perform dissimilar metal coating treatment on
This is a method for coating an aluminum-based cladding material with a dissimilar metal, which is characterized by the following steps.

Next, the present invention will be explained separately into a chemical conversion treatment process, an electroless plating process, and a metal coating process.

■Chemical conversion treatment process Chemical conversion treatment liquids that corrode aluminum-based craft materials should be avoided, and pure water is most preferable. When the chemical conversion treatment solution is heated to 80°C or more and the above-mentioned Cla-7-do is added, a reaction as shown in the following formula occurs regardless of the electrical method, forming a dense and protective boehmite film on the aluminum. be done.

28]+ 6 H,0→A11O,・nH2O+ (
3-n) If, 0+311, The lower limit of the processing time is determined by the masking effect in the subsequent electroless plating process, and the upper limit is determined by the etching effect of the metal halide during the substitution reaction between the metal halide and aluminum. Usually it is 3 to 1 minutes.

■Electroless plating process Electroless plating is used to withstand molten halide metal that wraps around non-aluminum surfaces in the subsequent metal coating process and aluminum halide gas generated by substitution reactions, and also to be used for Boehmite masking. The plating process does not require any special treatment.

■Metal coating process A halide such as copper, zinc, lead or tin is brought into contact with the aluminum surface of the aluminum-based cladding material, heated to a temperature above which a substitution reaction occurs between the aluminum and the metal halide, and then cooled to form a residue. remove. Through this step, the Hemai 1 film on the aluminum surface is removed by the etching action of the metal halide, and the substitution reaction between the metal halide and aluminum and the diffusion reaction between the metal atoms reduced and precipitated by the substitution reaction and the aluminum atoms. The metal coating is performed by At this time, the other side that has been electrolessly plated will not be corroded at all.

This includes other methods.

〔Example〕

An aluminum-based cladding material W (see Fig. 2 (A)) made of iron 1 and aluminum 2 that has been degreased and rusted is immersed in boiling ion-exchanged water 3 for 5 minutes to form a chemical conversion film 4 on the aluminum surface. (See Figure 2 (B)).

Next, the aluminum-based cladding material W is immersed in a 10% sulfuric acid solution for 3 minutes to activate it, and then immersed in an electroless nickel plating solution 5 at 60° C. shown in the following table for 5 minutes and taken out. C)), washed with water and dried, and nickel plating 6 was applied on the iron surface 1. At this time, nickel was not even scattered on the aluminum surface portion 4 that had been subjected to the chemical conversion treatment.

In addition, when the above-mentioned electroless plating is applied to the aluminum-based cladding material W which omitted the chemical conversion treatment process, and when electroplating is applied after the chemical conversion treatment process, plating crotches are also formed on the aluminum surface. However, the adhesion is extremely poor compared to ironwork plating.

Finally, apply petroleum jelly evenly and thinly to the chemically treated aluminum surface 4 of the aluminum cladding material W.
Cuprous chloride crystal IX &8'1 powder was sprayed and adhered to the coated surface, and then the cladding W was inserted into the furnace and heated for 45 minutes.
It is heated to near 0° C. to remove the chemical conversion film by etching, and at the same time, a substitution reaction occurs between aluminum and cuprous chloride as shown in the following formula.

AI+ 3 CuCl→3 Cu181c13 1st chloride
Five minutes after the copper melted, a product was obtained in which each of the cladding materials W was coated with nickel (see FIG. 2(D)).

〔Effect of the invention〕

As mentioned above, chemical formation automatically removed in the post-process = 10
- Applying a coating to the aluminum clad material to facilitate single-sided electroless plating, and further coating the aluminum with a different metal using the electroless plating as a mask, facilitates the dissimilar metal coating treatment of the aluminum clad material. Ta. Non-aluminum surfaces are protected by electroless plating and are not corroded by molten metal halide or aluminum halide gas. The product obtained according to the present invention can be made double-sided and can be subjected to surface treatment if necessary, and as shown in Fig. 2,
The end faces are also coated with different metals. This was not possible with the two-piece welding method.

The present invention is not limited to the above-mentioned embodiments, but can be widely modified without departing from the gist of the claims.

For example, electroless plating includes nickel, copper, cobalt, etc., alloy plating based on the above metals, and dispersion plating in which silicon carbide, alumina particles, etc. are dispersed, and the metal halides used in the metal coating process include: It includes copper halides such as cuprous chloride, cupric chloride, and copper bromide, tin halides such as tin chloride, and tin iodide, as well as halides such as silver, nickel, zinc, and titanium.

4. The simple explanatory drawings are explanatory drawings of the present invention, Figure 1 is a process diagram, and Figure 2 is a process diagram.
The figure is a diagram of an example.

1; Iron 2; Aluminum 3; Ion exchange permanent 4;
Aluminum surface portion 5 treated with chemical conversion film; electroless nickel plating solution

Claims (1)

[Claims] The first step is to form a chemical conversion film on the aluminum surface by immersing a cladding material (hereinafter referred to as aluminum-based cladding material) whose one side is made of aluminum or aluminum alloy (hereinafter simply referred to as aluminum) in pure water or an aqueous solution at a temperature of 80°C or higher. a second step of applying electroless plating to a non-aluminum surface using the chemical conversion film as a mask;
The third step is to bring a metal halide into contact with the aluminum surface and heat the aluminum surface to a temperature above which a substitution reaction occurs between the metal halide and aluminum to coat the aluminum surface with a different metal.
A method for coating an aluminum-based clad material with a dissimilar metal, the method comprising the steps of: