Process for increasing alloying rate of galvanized coating on steel

A process of providing a zinc-iron alloy surface coating on a zinc hot-dip coated ferrous metal strip without requiring heating the strip after withdrawing said strip from a hot-dip coating bath comprising;

• applying a coating of metallic copper to a clean lateral surface of a ferrous metal strip, heating said strip in a reducing atmosphere to a temperature between about 704.degree. C. and about 927.degree. C. (1300.degree. F.-1700.degree. F.) to effect diffusing a portion of said copper into said strip while leaving a film of metallic copper on the surface of the strip, immersing said strip in a hot-dip zinc coating bath to provide thereon a metallic zinc coating over said film of metallic copper, controlling the thickness of said metallic zinc coating to a maximum thickness of about 0.1 mil as said strip is withdrawn from said bath, and allowing the zinc coated strip to cool to ambient temperature without further heating said strip;
• whereby all the metallic zinc remaining in said coating forms a zinc-iron alloy as said strip is allowed to cool to ambient temperature.

A process of increasing the zinc-iron alloy growth rate when hot-dip galvanizing a ferrous metal strip comprising;

• applying a coating of metallic copper to a clean lateral surface of a ferrous metal strip, heating said strip to a temperature between about 704.degree. C. and about 927.degree. C. (1300.degree. F.-1700.degree. F.) in a reducing atmosphere to effect diffusing a portion of said copper into said strip while leaving a film of metallic copper on the surface of said strip, thereafter immersing said strip in a hot-dip zinc coating bath to provide a metallic zinc coating over said film of metallic copper, heating said strip to alloy all the zinc applied over said film of metallic copper and thereby provide a zinc alloy surface coating on said ferrous metal strip.