Hard electroplated coating for metals, esp. steels - contains cobalt, tungsten and tungsten carbide, and is heat treated to obtain high corrosion resistance, esp. to sea water

摘要

A metal substrate is electroplated in a bath contg. the salts of Co and W, but no Cr; and particles of tungsten carbide are suspended in the bath. The hard coating thus obtd. is then heat treated so it is consolidated and bonds to the substrate; the coating thickness and the short heating times ensures that less than 2% of the substrate metal is on the surface of the coated prod. The substrate is pref. steel 100-C-6; or steel Z-100-CD; and the pref. bath contains CoSO4, CoC12, Na2WO4, and less than 300 g/l powdered W-C. The bath pH is pref. 4-5.5, obtd. by adding boric acid. The coating resists a variety of corrosive media without cracking, and is esp. useful for ball bearings exposed to marine atmos.