Continuous hot dip coating of metal strip with metal - where another powdered metal is sprayed onto molten coating to form composite layer with increased corrosion resistance

摘要

Metal strip (a) is fed through a bath of molten metal (b) to form a coating (b). Before coating (b) has solidified, the strip is next fed through streams of gas contg. a metal powder (c), so that metal (c) enters coating (b) to form a composite structure (b,c) with better corrosion resistance than when only coating (b) is used. Coating (b) is pref. provided with 0.1-15%, esp. 0.5-3% of metal (c); and metal (c) pref. has a higher m.pt. than metal (b). Coating (b) is pref. Zn; a Zn-Al alloy; or a Zn-Fe alloy; whereas metal (c) is pref. Ni or its alloys. The pref. appts. includes nozzle boxes spraying powder (c) in a gas onto strip (a) leaving a bath of metal (b).