Black fasteners on Japanese motorcycles: smart finish clues

Summary for black fasteners on japanese motorcycles Discussion

Black fasteners on Japanese motorcycles are discussed as likely being more than one finish, since older parts can start semi-gloss black and later turn olive-green while newer ones stay glossier and more stable. Barry asks about the black surface finish used on steel fasteners, brackets, and similar hardware on late-1970s to current Japanese motorcycles, especially for refinishing an old Yamaha DT and Honda CBX. The reply from Ted Mooney says that unless someone knows those exact motorcycles, any identification is partly a guess, but zinc or zinc-alloy plating with black chromates is very common. He suggests the older fasteners were probably zinc plated with a black silver-bearing chromate that discolors over time, while newer ones may be zinc-iron alloy plated with a black chromate that does not use silver and therefore does not discolor as much.