Use of the Scanning Reference Electrode Technique for the Evaluation of Environmentally Friendly, Nonchromate Corrosion Inhibitors

The scanning reference electrode technique (SRET) has been used to study the influence of a range of anodic and cathodic corrosion inhibitors on patterns of localized corrosion occurring on the intact zinc surface of galvanized sheet steel. SRET spatially can resolve localized anodic and cathodic activity occurring across the zinc surface and has highlighted some promising novel inhibitor species (i.e., rare-earth metal salts containing cerium [III], lanthanum [III], and yttrium [III] cations). Conversely, anodic inhibitor systems containing tungstate (WO42−) and molybdate (MoO42−) anions have been shown to induce severe pitting corrosion accelerating perforation of the zinc coating and exposing the steel substrate.