Trivalent passivates need trivalent post-dips

The application of hexavalent chromium for conversion coatings reflects on a long and successful history in corrosion-resistant coatings starting in the early 1930s.1 Although chromium(III)-based conversion coatings date back as early as 1951,2 their industrial application was forced into practice by the European End-Of-Live-Vehicle (ELV) directive.' In addition, the RoHS4 and WEEE5 directives preclude chromium(VI) from being used in metal coatings in electrical and electronic equipment. Therefore, the use of hexavalent chromium is actually limited to a rather small number of remaining applications.