Abstract: Excessive evolution of hydrogen in electrolytic deposition of metals on a cathode substrate can be controlled by using a pulsed reverse current. Reverse current pulses interposed between the forward current pulses consume at least some of the nascent hydrogen and prevent the local pH at the cathode surface from becoming excessively alkaline. Control of hydroxide ion concentration by pulsed reverse current alleviates problems caused by reaction of metal-bearing-ions with hydroxide ions generated near the cathode by evolution of hydrogen. The method is useful in depositing functional chromium coatings on electrically conductive substrates from plating baths comprising aqueous solutions of trivalent chromium salts. In such a method the current comprises forward pulses having a duty cycle of from about 50% to about 90% and reverse pulses having a duty cycle of from about 5% to about 30%, and a frequency of from about 5 Hz to about 700 Hz.

Abstract: Metal salts are removed from solution in an electrolyte by subjecting the solution to electrolysis in a cell having an anode that has an anion exchange membrane closely associated therewith which sequesters the anion of the salt. The cathode may also be provided with a closely associated cation exchange membrane that sequesters, at least partially, the cation of the salt. A metal salt solution can be regenerated by reversing the polarity of the electrodes and conducting an electrolysis using fresh electrolyte.