Gold Passivation in Aqueous Alkaline Cyanide

Abstract

The behavior of gold electrodes in alkaline cyanide solution was studied using potentiostatic and potentiodynamic techniques. The results showed that the three anodic current peaks found in both steady‐state and potential sweep experiments resulted from passivation of the gold cyanide dissolution reactionPotential pH measurements showed that the passivating reactions were dependent on the hydroxyl ion concentration. The potentials at which passivation occurred closely corresponded to the formation potentials of gold oxide and suboxide surface species. It was concluded that the most anodic dissolution reaction (peak 3) was passivated by the formation of gold (III) oxide. The less anodic gold dissolution peaks, peaks 1 and 2, were passivated by the formation of gold (I) hydroxide according toFrom the remarkable similarity between the location of the gold dissolution peak in alkaline cyanide solution and the location of the oxide and suboxide peaks in cyanide‐free alkaline solution, it was concluded that peaks 1 and 2 corresponded to gold dissolution and subsequent passivation predominantly on the (100) and (111) crystal planes, respectively; whereas peak 3 corresponds to gold dissolution and subsequent passivation over the complete electrode surface.