ZINC-NICKEL ALLOY PLATED STEEL SHEET HAVING EXCELLENT ADHESION PROPERTY TO CHROMATE FILM, GOOD SURFACE APPEARANCE AFTER CHROMATE TREATMENT AND ORGANIC RESIN COATING TREATMENT AND EXCELLENT CRATERING RESISTANCE AFTER ELECTRODEPOSITION COATING AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To improve the adhesion property to a chromate film, in particular, surface appear ance after a chromate treatment and org. resin coating treatment, etc., of a Zn-Ni alloy plated steel sheet. ;SOLUTION: This Zn-Ni alloy plated steel sheet comprises a first layer consisting of a Zn-Ni alloy plating film which has 10 to 16 wt.% Ni content, a second layer consisting of a Zn-Ni alloy plating film which is distributed substantially uniformly with Ni over the entire part of the surface thereof and is a thin coating weight and a third layer consisting of a Zn-Ni-P composite film which is distributed substantially uniformly with Ni and P over the entire part of the surface thereof and is an extremely thin coating weight. This process for producing the Zn-Ni alloy plated steel sheet consists in subjecting the steel sheet to a surface reforming treatment comprising subjecting the steel sheet to a first electroplating treatment by the conventional method of a current density exceeding 40A/diameter², then subjecting the steel sheet to a second electroplating treatment at a low current density of 10 to 50% at the time of the first electroplating treatment and immersing the steel sheet into an aq. phosphate soln. of a pH above 3.;COPYRIGHT: (C)1999,JPO