HIGH CORROSION RESISTANT STEEL SHEETS WITH TWO LAYER BEING OF ALLOY METAL AND PROCESS FOR MAKING

摘要

A high anticorrosion alloy electroplated steel plate consists of (1) the lower electroplated surface layer comprising with zinc electroplated layer, having the thickness of at least 10 g/m2 on one side of steel plate and (2) the upper layer comprising with Fe-Zn-Mn alloy electroplating layer which contains 5-30 wt.% zinc, 0.1-10 wt.% manganese and the residual iron, having a thickness of 0.5 g/m2. The bilayered alloy steel plate is electroplated by controlling and applying to the following conditions: (a) the total metallic concentration has the range from 0.5 mol/l to the critical solubility, (b) the mount of zinc ion and manganese ion in this concentration is 1-40 mol.%, (c) the ionic concentration of chloride is 5.0-1.0 mol, and the pH of chloride is 1.0-4.0, (d) the current density in the chloride bath is 250 A/dm2 and the relative flow velocity is 20-200 m/min.