Chrome plating using trivalent chromium solns - esp for ABS plastics, with greater covering power and easier effluent removal

摘要

A chromium plating soln. based on trivalent Cr contains 0.1-1.2M Cr (III), 0.01-1M Br-, >=0.1M NH4, >=0.1M borate, formate or acetate in the ratio 0.5:1-3:1 w.r.t. Cr, and opt. >=0.5M Cl- or F-, and =5M SO2-4. Pref. concn ranges are 0.2-0.6M Cr (III), 0.05-0.3M Br-, 1-3M NH4, 0.5-1M borate, formate or acetate 1:1-2:1 w.r.t. Cr, 1.5-5M cl1, 0.5-4M SO4, with total (SO4 + Cl) 2.5-3.5. The soln. operates with pH 1-4, pref. 2-3.5, at 15-30 degrees C using carbon anodes and the plating range is 0.5-110 A/dm2. A cation, e.g. Fe, which codeposits with Cr may be added. The soln. is suitable for plating on ABS; it has greater covering power and easier effluent disposal than Cr(VI) solns.