JP2857775B2 - Oxidation resistance treatment method for metal surface - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surface treatment method for preventing oxidative corrosion of a metal.

[Prior Art] As a treatment method for imparting oxidation corrosion resistance to a metal, there are known methods such as rust prevention treatment, chromate treatment, and resin coating by adsorption of an organic compound to a metal surface. However, depending on these methods, it cannot be expected that the metal treated at a high temperature such as 500 ° C. will exhibit a sufficient oxidation corrosion resistance.

On the other hand, it is known that by plating a metal with nickel, the treated metal can exhibit a sufficient antioxidant effect even at a high temperature such as 500 ° C. However, in this case, the surface of the plated nickel is oxidized and blackened, and not only the appearance is impaired, but also if it is kept at a high temperature for a long time, the oxidation of the nickel further progresses, and finally the plated metal is bent. Cracks occur on the metal surface due to the above-mentioned factors, and the nickel-plated surface layer peels off.

[Problems to be Solved by the Invention] Therefore, even at a high temperature such as 500 ° C., it is possible to sufficiently prevent oxidative corrosion of a target metal, and a plated layer or the like formed on a surface even after bending a treated metal is bent. It has been necessary to find an oxidation-resistant treatment method for a metal surface that does not peel off and fall off.

[Means for Solving the Problems] After forming a nickel plating layer on a metal surface, forming an indium plating layer, and then forming a nickel plating layer on the indium plating layer, the above-mentioned problems are solved. Could be solved. In this case, it is appropriate that the thickness of the indium plating layer is 0.05 μm to 5 μm. 0.
If the thickness is less than 05 μm, the effect of the above two-layer plating is not sufficient, and if the thickness reaches 5 μm, the effect is saturated, and if the thickness exceeds 5 μm, simply increasing the thickness merely increases the cost. is there. It is also appropriate that the thickness of the nickel plating layer provided on the indium plating layer is 0.05 μm to 5 μm. The reason is exactly the same as that described for the thickness of the indium plating layer.

The metal that can be surface-treated by the method of the present invention is not particularly limited as long as it can form a plated layer of indium or nickel stably, but is mainly copper, iron or the like. Indium can be plated directly on the surface of the metal to be protected and nickel can be plated on it.However, after forming an undercoat layer of nickel plating on the metal surface, an indium plating layer is formed, and nickel is further formed thereon. Plating provides an improved effect. The thickness of the nickel plating layer to be subbed is not particularly limited, but it is appropriate to set the thickness in the range of 0.05 μm to 5 μm for the same reason as described for the thickness of the layer plated thereon. .

[Operation] According to the present invention, as described above, a nickel plating subbing layer is provided on a metal surface, an indium plating layer is provided thereon, and a nickel plating layer is further provided thereon to form a three-layer protective plating layer. When formed, when a metal having a three-layer plating layer is exposed to a high-temperature atmosphere such as 500 ° C., thermal diffusion occurs between the indium plating layer and the nickel plating layer, and indium and nickel are formed at the interface between the two. It is understood that an intermetallic compound of the formula (1) is formed, and since this intermetallic compound exhibits excellent oxidation resistance, a coated metal having a sufficient antioxidant effect can be obtained even at a high temperature such as 500 ° C. The melting point of indium alone was as low as 156.6 ° C., but it was confirmed that the formation of the intermetallic compound formed a protective layer of an intermetallic compound having a high melting point which did not melt even at 550 ° C.

[Example] According to the present invention, as shown in FIG. 3 (a), after a nickel plating layer having a thickness of 2 μm was provided around a copper wire having a diameter of 5 mm, an indium plating layer having a thickness of 0.5 μm was formed thereon. Then, a nickel plating layer having a thickness of 0.5 μm was further provided thereon. Each of the plating layers was formed by an electroplating method.

On the other hand, for comparison, as shown in FIG. 3B, a nickel plating layer having a thickness of 3 μm was formed by electroplating around the same copper wire having a diameter of 5 mm as described above.

FIG. 1 shows the results of a test for evaluating the oxidation resistance of the two types of copper wires having different surface treatments. That is, the weight increase per 10 cm of each copper wire sample measured after holding each copper wire sample at 550 ° C. in the air for 5 days, 10 days, 15 days and 20 days, respectively, is as shown in the figure. It can be seen that the coated copper wire of the present invention plated with nickel on the plating has a smaller weight increase and a lower oxidation rate than the comparative coated copper wire simply plated with nickel. After holding at 550 ° C. for 20 days, when the copper wire sample was bent, the one treated by the method of the present invention did not peel off, but the copper wire sample of the comparative example had a part of the surface due to bending. Peeled off.

The pattern of the change in the resistance value of each copper wire sample measured after holding at 550 ° C. for 5 days, 10 days, 15 days and 20 days in the air atmosphere is as shown in FIG. It is clear that the copper wire sample treated with has a smaller increase in resistance and an improved oxidation resistance of the copper wire as compared with the copper wire sample for comparison. In FIG. 2, the resistance value is
Relative values are shown assuming that the resistance value before entering the atmosphere at 550 ° C is 100%. The resistance value was measured in an atmosphere at 25 ° C. after holding in an atmosphere at 550 ° C.

The results of the above comparative test clearly show that the copper wire surface-treated by the method of the present invention has a small increase in resistance and has an oxidation resistance.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the number of days that a copper wire sample was kept in an air atmosphere at 550 ° C. and the weight increase of the copper wire. FIG. 2 is a graph showing the relationship between the number of days when a copper wire sample was kept in an air atmosphere at 550 ° C. and the resistance value of the copper wire. FIG. 3 is a cross-sectional view of a copper wire covered with nickel, indium and nickel plating layers by the method of the present invention (a) and a conventional copper wire covered with only a nickel plating layer (b). .

Claims (2)

(57) [Claims] An oxidation-resistant method for a metal surface, comprising: forming a nickel plating layer on a metal surface, forming an indium plating layer thereon, and further forming a nickel plating layer thereon. 2. The indium plating layer has a thickness of 0.05 μm.
2. The method according to claim 1, wherein the thickness of the nickel plating layer is in a range of 0.05 μm to 5 μm, and the thickness of the nickel plating layer formed thereon is in a range of 0.05 μm to 5 μm.