| 摘要 |
PROBLEM TO BE SOLVED: To provide a highly corrosion resistant nickel-gold plating realized in high corrosion resistance without so sacricifying its cost and productivity. SOLUTION: In a layer structure in which the surface of a base metal 1 is provided with nickel plated layers, and further the surface is provided with a gold plated layer 4, the nickel plated layers are composed of two layers i.e., upper and lower layers, and the lower first nickel plated layer 2 has a corrosion potential nobler than that of the upper second nickel plated layer 3. In this way, the first nickel plated layer 2 is protected by the sacrificial corrosion inhibition effect of the second nickel plated layer 3 even in the corrosive environment. Thus, the corrosion rate of the first nickel plated layer 2 by pitting corrosion is slow, and sufficient durability is attained without thickening each plated layer so much.
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