High speed chromium plating soln. - has defined sulphuric acid to chromic acid ratio and contains addns. of hydrogen peroxide

摘要

The cr plating soln. contains 40-500 g/l CrO3, a high concn. of sulphuric acid varying from 1-90 calcd. on the CrO3 content, and in add. Cr3+ formed by a reducing agent H2O2 used in an amt. of 40-200 g/l. The ratio of sulphuric acid to CrO3 in the soln. is 1 : 2 to 1 : 10 in the range of 40-100 g/l CrO3, or 1 : 10 to 1 : 80 in the range of 50-200 g/l CrO3, or 1 : 30 to 1 : 90 at 200-500 g/l CrO3, in the latter case the soln. contains in addn. 40-200 g/l 30% H2O2. The bath is used at a current density of 10-1000 A/100 cm2. Electrodeposition of a hard, bright or matt Cr coating is obtd. at an increased current yield, and high d. giving a saving in costs.