PRODUCTION OF ZINC-CHROMIUM ALLOY ELECTROPLATED STEEL SHEET

摘要

PROBLEM TO BE SOLVED: To provide an industrially stable production method of a zinc- chromium alloy electroplated steel sheet having excellent corrosion resistance and corrosion resistance after coating. SOLUTION: A zinc-chromium alloy layer is formed by intermittently applying an electric current while suppressing production of polynuclear complex of a hydrated complex of chromium ion. As for an org. additive, a polyoxyalkylene deriv. comprising an ethylene oxide group having <=15 additional molar number and a hydrocarbon group of <=20 carbon number having an aromatic group of 4m+2 (m=1 or 2)π-electrons or a satd. hydrocarbon group having 2 to 10 carbon number is used. The current is applied in such a manner that the energizing time is 0.15 to 4.5sec with >=0.10 energizing ratio. Plating is carried out by controlling the flowing velocity of the plating liquid to >=30m/min.