PRODUCTION OF ZN-NI ALLOY PLATED STEEL SHEET HAVING EXCELLENT CORROSION RESISTANCE, PRESS POWDERING RESISTANCE AND SURFACE APPEARANCE

摘要

PURPOSE:To stably produce the title plated steel sheet by using a plating bath of a low Ni concn. and combining temp., pH, boundary flow rate, removal of gaseous hydrogen and current density under specific conditions. CONSTITUTION:The Ni2+ concn. of the Zn-Ni alloy plating bath is adjusted to =10g/l, the Zn2+ concn. to =15g/l in addition, the molar concn. of the Ni2+ and Zn2+ is adjusted to 0.48-1.48, the pH to 0.5-4.5 and the bath temp. to =50 deg.C, then the gaseous hydrogen is removed. A plating liquid is supplied from a slit part 6 to a plating cell installed with electrodes 4 in parallel with the steel sheet 3 and is filled between the electrodes 4 and vats 5. The plating is executed at =40A/dm2 current density by setting the tangent flow rate of the plating liquid at the boundary of the steel sheet at =5m/min. The current is simultaneously cut by the vats 5 in the central part of the plating cell and the liquid pressure in this part is regulated to the pressure higher by =100mm in water column than the liquid pressure in the part of the electrodes 4. The Zn-Ni alloy plated steel sheet having the excellent corrosion resistance, press powdering resistance and surface appearance is obtd. in this way.