PROCESS FOR PRODUCING STEEL STRIP ELECTROPLATED WITH ZINC ON BOTH SIDES IN CHLORIDE BATH.

摘要

Chloride bath precess for two-sided plating of steel strip in two plating stages with an intermediate wetting stage uses a wetting soln. with a Zn concn. of 0.1-50 g/l in the wetting stage. Wetting soln. temp. is normally 20-50 deg. C, its pH is pref. 3-6, and its components other than Zn are pref. the same as in the compsn. system used for the plating baths. In an example 20 g/m2 per side, two-side plating with a plating bath temp. of 55 deg. C and pH of 5.0; wetting bath temp. of 40 deg. C and pH of 4.5; line speed of 50 m/min and current density of 50 A/dm2 was effected using (1) a plating bath compsn. contg. 180 g/l ZnCl2 and 300 g/l NH4Cl and a wetting soln. with a Zn concn. of 4.6 g/l and contg. 10 g/l ZnCl2 and 20 g/l NH4Cl. (2) A plating bath compsn. contg. 220 g/l ZnCl2 and 350 g/l NaCl and a wetting soln. with a Zn concn. of 36 and contg. 75 g/l ZnCl2 and 100 g/l NaCl. This treatment gave a covering degree o of 100% in both cases and a glossiness degree of 50.3% and 44.6%.