THE ALTERNATIVE ELECTROCHEMISTRY OF GOLD

摘要

Metal corrosion reactions in aqueous media are often considered in terms of standard electrode potential (or Pourbaix) data; however, it is demonstrated that, after appropriate electrode activation (precathodization or severe thermal pretreatment, which are not uncommon) gold surfaces in aqueous media undergo significant oxidation at ca. 0.5 V (RHE), i.e. at ca. 1.0 V lower than the E° value for oxidation of this electrode system. On the basis of this and earlier work with other metals it is suggested that these systems exhibit two types of electrochemistries, namely, conventional electrochemistry and active metal/hydrous oxide, or anomalous, electrochemistry. The implications of the type of anomalous electrochemical behaviour in question here with regard to the breakdown of passivating oxide films and localized corrosion is briefly outlined.