Surface treated steel strip with minimal plating defects and method for making

Abstract

In connection with a process of implementing galvanizing and galvannealing on steel strips containing highly oxidizable elements such as Si, Mn, P, Ti, Nb, Al, Ni, Cu, Mo, V, Cr, and B, after annealing in a continuous line or implementing electroplating after annealing, the present invention provides a method for restraining non-plating at low cost in a stable manner and a surface treated steel strip having minimal non-plating. By applying on at least one surface of a steel strip a Fe plating having a coating weight of 0.1-10 g/m.sup.2 and an oxygen content of 0.1-10 wt %, followed by annealing and then zinc or zinc alloy plating, there is obtained a surface treated steel strip having minimal plating defects which includes a Fe plating layer immediately below a zinc or zinc alloy plating layer and a steel alloying element concentrated stratum immediately below the Fe plating layer. The Fe plating may be formed using an electroplating bath which contains 0.1-10 g/l of Fe.sup.3+ and a carboxylic acid or an alkali metal salt thereof.

Dependencies are inferred from the claim text.