Studies of chromium plating from low concentration electrolytes

Chromium plating is generally carried out from electrolytes containing chromic acid along with a small quantity of sulphate in the absence or presence of fluorine compound. Normally fairly concentrated solutions with 250 to 400 g/l chromic acid are used. Such a high concentration of chromic acid leads to excess drag-out losses. And higher effluent treatment costs. These considerations have necessititated investigations abroad on the usefulness of low concentration solutions. In this paper the authors highlights the results of studies on low concentration electrolytes. Experiments were carried out with varying concentrations of chromic acid from 50 g/l to 250 g/l in the presence of 1% sulphate by means of Hull cell tests in order to determine the basic solution composition. Current efficiency and rate of build-up were also determined in the case of selected compositions. The effect of boric acid or lanthanum oxide were investigations in certain solution composition