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 th e influence of a range of anodic and cathodic corrosion inhibitors on patte rns of localized corrosion occurring on the intact zinc surface of galvaniz ed sheet steel. SRET spatially can resolve localized anodic and cathodic ac tivity occurring across the zinc surface and has highlighted some promising novel inhibitor species (i.e., rare-earth metal salts containing cerium [I II], lanthanum [III], and yttrium [III] cations). Conversely, anodic inhibi tor 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.