Behavior of Salicylaldoxime and 8‐Hydroxyquinoline at a Copper Electrode

Effects of salicylaldoxime (SAO) and of 8‐hydroxyquinoline (HQ) on the anodic dissolution of copper were studied by using a potentiokinetic polarization method and phase‐selective a‐c polarography at a rotating copper disk electrode at various p H values. At p H 1.5, where cupric ions do not precipitate as the chelates of SAO and HQ, the anodic dissolution of copper was retarded slightly by these additives. At p H 2.8 and 5.0, where SAO precipitates cupric ions quantitatively, the anodic dissolution of copper was markedly retarded by SAO, especially from the rotating disk electrode. The anodic polarization curves of copper in the SAO solutions were similar to those obtained in the passivation of iron. A thin protective chelate film was formed on the copper electrode. At very positive potentials, the chelate film ruptured and the anodic dissolution of copper started. On the other hand, HQ chemisorbed strongly on the copper electrode from p H 2.8–5.0, where HQ also precipitates cupric ions, and the copper dissolution was retarded markedly. The Cu‐HQ chelate did not act as a barrier for the copper dissolution in this p H range.