Metal member with chromate coat, spark plug with chromate coat and manufacturing methods thereof

摘要

A metal member 55 (with a zinc plating layer 56 for prevention of corrosion) having a sliding expected surface that is expected to slide with the other member is immersed into a chromating bath containing a mixture of trivalent chromium salt and a complexing agent for trivalent chromium. And a chromate coat 57 having a film thickness of 0.2 to 0.5 mu m and composed of trivalent chromium at 95mass% or more of chromium component contained is formed at least on the sliding expected surface. Thereinafter, its chromate coat 57 is subjected to the heat treatment at temperatures from 85 to 255 DEG C, thereby enhancing the sliding property of the chromate coat 57. As a result, the metal member 55 with chromate coat can be easily slid with the other member. <IMAGE>