Chromising of ferrous substrates in molten lead bath - using low chromium content to reduce roughness and porosity of coating

摘要

A ferrous-based substrate is chromised by diffusion coating from a molten alloy bath consisting mainly of lead and contg. 0.85% chromium based on the weight of Pb, Pb being the only transfer agent in the bath and Cr pref. being the only diffusing element. Reduction of the Cr content of the bath results in reduced Cr concn. in the coating, giving improved ductility and malleability while still imparting adequate corrosion resistance and reducing costs. In addition, the risk of producing a rough, porous coating, which can occur during cooling of the bath due to Cr precipitating out of soluion, is reduced.