PURPOSE: To obtain a rust preventive steel sheet thin in coating weight and excellent in corrosion resistance by forming a Ni-P based alloy plated layer containing a specific quantity of P on the surface of the steel sheet, heat treating to form a diffused alloy zone mainly containing Fe-Ni-P on the boundary and further zinc electroplating.
CONSTITUTION: The diffused alloy zone mainly containing Fe-Ni-P is formed on the boundary between the bare surface of the steel sheet and the plated layer by forming Ni-P based plated layer containing 8-15% P or a Ni-P based alloy plated layer containing ≤15% one or more kind of W, Mo, Cu on at least one surface of the cold rolled steel sheet and heat treating the steel sheet in a non-oxidizing atmosphere. the steel sheet is zinc electroplated. As a result, the rust preventive steel sheet thin in coating weight and excellent in corrosion resistance is obtained.
ABE MASAKI
WATANABE TOYOFUMI
SHIOBARA YUKIMITSU
