Indole and 5-chloroindole as inhibitors of anodic dissolution and cathodic deposition of copper in acidic chloride solutions

The effect of indole, IN, and 5-chloroindole, Cl-IN, on the anodic dissolution of copper in acidic sodium chloride solutions was studied using voltammetry on a rotating disc electrode (RDE). Both compounds used at 10(-3) M concentration act as strong inhibitors on the copper dissolution, but indole exhibits better inhibiting properties. The inhibitory action substantially increases with decreasing solution pH. The influence of these organic additives on the electrodeposition of copper on platinum was also investigated using RDE and electrochemical quartz crystal microbalance (EQCM) techniques. The EQCM measurements show that a sparingly soluble layer of the inhibitor is responsible for the protective effects observed in chloride solutions.