JPH0312145B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for copper plating stainless steel. Copper plating has traditionally been applied to household goods and various other industrial products, but it is said that products made from mild steel and other iron alloys will rust when the copper plating wears out after long-term use. Due to these problems, attempts have been made to use stainless steel as the material. However, it is currently not put to practical use because direct electrolytic copper plating or chemical copper plating cannot be applied to stainless steel. On the other hand, in recent years, metal thermos flasks made of stainless steel have come into practical use in place of glass thermos flasks that have poor impact resistance. Stainless steel has the advantages of excellent corrosion resistance, strong mechanical strength, and low thermal conductivity, but it has a significantly high thermal emissivity.
Similar to glass thermos flasks, it has been reported, for example, in Japanese Patent Publication No. 57-22571 and Japanese Unexamined Patent Publication No. 57-57, that heat transfer due to radiation is reduced by forming silver mirrors on the walls of the inner and outer bottles that surround the vacuum space of stainless steel thermos flasks. −
This was proposed in Japanese Patent No. 75621, and the latter also discloses copper plating via nickel plating. A stainless steel thermos flask with a silver mirror layer exhibits sufficient heat retaining power for practical purposes, but since the cost of silver is extremely high, there is a problem in that the manufacturing cost of the thermos flask is extremely high. Additionally, a thermos flask with a copper plating formed with a nickel plating interposed therein also exhibits sufficient heat retention for practical purposes, but since the copper plating cannot be formed on the stainless steel base as it is, the nickel plating must be formed. Each member constituting the inner bottle and outer bottle, for example, a body member,
Since the neck member and the bottom member must be plated and then joined together, there is a problem in that the manufacturing process is complicated and requires a large number of man-hours. The purpose of the present invention is to solve these problems and provide a method that can easily form a homogeneous, adhesive, and high-quality copper plating on a stainless steel surface. A method for copper plating stainless steel, which is characterized by firing in an oxidizing atmosphere and then chemically copper plating the surface of the stainless steel. In other words, in the present invention, even if the stainless steel substrate is chemically plated with copper, if it occurs on the surface of the substrate due to the chemical reaction described below, the precipitation of copper will be inhibited by hydrogen, and even if it does precipitate, it will crack or peel. Therefore, it is impossible to achieve good copper plating, but when the surface of the stainless steel base is moderately oxidized, an oxide film consisting mainly of ferric oxide is formed, and this oxide film prevents copper precipitation. This was completed based on the knowledge that it is possible to accelerate the formation of a copper plating layer with good adhesion. The chemical reaction in alkaline divalent copper solution is as follows. Cu ⁺⁺ +2e ^- →Cu↓ 2HCHO+2OH ^- → 2HCOO ^- +2H ₂ O+2e ^- +H ₂ ↑ In a preferred embodiment of the present invention, in order to promote copper precipitation, after the oxide film is formed and before chemical copper plating, The surface of the oxide film is activated by immersing it in a solution containing palladium chloride as a main component. Further, instead of immersing in a solution containing palladium chloride as the main component, or after immersing in the solution, activation is performed by immersing in a solution containing stannous chloride as the main component. In another preferred embodiment, the firing process is performed at 250-550°C, preferably at 300°C, to ensure strong adhesion of the copper plating layer to the stainless steel surface.
It is preferable to carry out the reaction at a temperature of -450°C, and the time varies depending on the temperature, but it is usually 5 to 180 minutes, preferably 10 to 60 minutes. This is because if the firing temperature is less than 250°C, a sufficient oxide film will not be formed or it will take a long time to form, leading to an increase in manufacturing costs, and if the firing temperature exceeds 550°C, the stainless steel base will undergo transformation. be. In addition, the firing time can be set arbitrarily as long as it is within the above temperature range, but
If it is less than 5 minutes, it will be difficult to form a sufficient oxide film when the firing temperature is low, and if it exceeds 180 minutes, if the firing temperature is high, the firing process will be performed more than necessary, which will increase the energy loss and cause the copper to burn again. It is desirable to perform the firing within the above range because the precipitation of . According to the method of the present invention, copper plating on stainless steel is performed by first oxidizing the surface of the stainless steel by firing treatment, and then immersing it in a chemical copper plating bath, but the degree of oxidation changes after firing. It is preferable that the glossiness of the stainless steel surface is 10 to 50 lower than the glossiness of the polished surface before firing. This is because oxidation that causes a decrease in gloss of less than 10 cannot cause a copper precipitation reaction on the stainless steel surface, and excessive oxidation that causes a decrease in gloss of more than 50 cannot cause a copper precipitation reaction. This is because it becomes difficult. The cause of this phenomenon is
Although it is not completely understood, in unfired or similar conditions, sufficient ferric oxide, which contributes to copper precipitation, is not formed, and when oxidized excessively, there is no ferric oxide on the surface, and almost no ferric oxide exists on the surface. It is presumed that this is because only chromium oxide is present, which inhibits the precipitation of copper. Usually, as long as the firing is carried out under the above-mentioned firing conditions, the change in the glossiness of the stainless steel surface will fall within the above-mentioned range, so there is no need to particularly measure the glossiness after firing. Further, as the stainless steel, there is no problem with any of the austenitic, ferrite, and steanite stainless steels. Chemical copper plating on stainless steel with an oxide film can be performed as is, but in order to promote copper precipitation and form a practical copper plating film, one of gold, platinum, palladium, and silver is used. of precious metals for a short period of time, usually 5
It is preferable to immerse at room temperature for seconds to 5 minutes. Also,
Thereafter, it is preferable to activate it by immersing it in a bath containing stannous halide as a main component at room temperature for a short period of time. The chemical copper plating bath is not particularly limited as long as it is an alkaline copper bath, regardless of whether it contains additives, and any commercially available bath may be used. Examples of the present invention will be described below. Example 1 A 0.3 mm thick stainless steel (SUS 304) test piece (50 x 150 mm) was prepared, and after buffing it,
It was degreased using trichlene and acetone and then calcined in air at 350°C for 20 minutes. Next, it was immersed in an aqueous solution containing 0.1 g of palladium chloride for 30 seconds at room temperature, then immersed in an aqueous solution containing 10 ppm of tin chloride for 10 seconds at room temperature, and washed with water. This was immersed in a chemical copper plating bath prepared according to the following recipe at 22℃ for 10 minutes to deposit copper on the stainless steel surface, then washed with water and dried to form a smooth, high-quality copper plating with good adhesion. We were able to. (Formulation of chemical copper plating bath) After dissolving 170g of Lotusel salt in 1 water,
Dissolve 50g of sodium hydroxide and add copper sulfate.
The solution obtained by dissolving 35 g is called Solution A, while the 40 w/v% formaldehyde aqueous solution is called Solution B, and these are mixed at a ratio of 100:30 to prepare a chemical copper plating bath. In order to check the adhesion of the plating layer obtained in this way, I rubbed it strongly with my fingertips, but it did not peel off at all, and no abnormality was observed even after it was left in a high vacuum at 450°C for several hours. . The gloss of the surface of the test piece after buffing and degreasing was 122, and the gloss after firing was 101, which was 21 lower than before firing. This gloss value is
Based on the measurement method specified in JIS Z8741, a digital variable angle gloss meter (Model: UGV-) manufactured by Gas Test Instruments Co., Ltd.
4D), the incident angle is 60°, and the standard sample's glossiness of 91.1 is set to 22.8, which is 1/4. Comparative Example 1 Chemical copper plating was performed using the same method and conditions as in Example 1 except that the firing process was omitted.
A cracked copper plating layer was only formed here and there on the surface of the test piece, and most of it peeled off when pressed with a fingernail. Examples 2 to 7 and Reference Examples 1 to 3 Chemical copper plating was carried out in exactly the same manner as in Example 1 except that the firing conditions were changed to those shown in Table 1. These results were compared to the gloss level after firing and Comparative Example 1.
The results are shown in Table 1.

【table】

[Table] As is clear from the above description, according to the present invention, high-quality copper plating with good adhesion can be obtained by the simple operation of chemical copper plating after firing, unless conventional nickel plating or the like is used. Things that are impossible become possible. Furthermore, when the method of the present invention is applied to the production of high-vacuum insulation containers such as stainless steel thermos flasks, it is possible to sinter the inner and outer bottle components without requiring the complicated process of intervening conventional nickel plating. After assembling the heavy-walled structure, it is only necessary to apply chemical copper plating, which improves work efficiency.Moreover, copper plating has the same thermal emissivity as a silver plating layer, so it is possible to create a high-vacuum insulated container with excellent heat retention. It has excellent effects such as being able to be manufactured at low cost. In addition, in the process of firing the inner and outer bottles, there is also a degassing effect from the stainless steel, which has the effect of shortening the evacuation time.

Claims (1)

[Claims] 1. A method for copper plating stainless steel, which comprises firing the stainless steel in an oxidizing atmosphere, and then chemically plating the surface of the stainless steel with copper. 2. The method of claim 1, wherein the fired stainless steel surface is activated with an aqueous palladium chloride solution prior to chemical copper plating. 3 Stainless steel in an oxidizing atmosphere at 250-550℃
3. The method according to claim 1 or 2, wherein the method is performed by firing with.