Electrodeposition of chromium with periodic reverse and pulsed current

Abstract

Abstract : The report covers an investigation of the effects of periodic reverse current and pulsed direct current on properties and metal distribution of chromium electrodeposits. The plating current was reversed for short periods of various lengths during deposition of chromium at various current densities and in baths at several concentrations of chromium trioxide or CrO3. Several chemicals were added to the standard bath in an effort to further improve deposit distribution during periodic reverse (PR) plating. Several of the chemicals tried as well as the lower bath concentrations were effective in improving distribution in addition to the improvement obtained with PR. Thickness ratios of less than one were obtained on some panels and screw threads were plated with a ratio as low as 1.3 using PR. Small but definite improvements in the distribution of chromium deposits were obtained using pulsed dc current with the most uniform thickness obtained in the dilute bath. Also, nearly all deposits from the dilute bath were bright over a range of pulse times.