Corrosion Resistance of Cerium doped silica sol gel coatings on AISI 304 substrates

A. PEPE,; M. APARICIO,; A. DURÁN,; S. CERÉ

Los Angeles, USA

Congreso; International Sol-Gel Meeting; 2005

AISI 304 Stainless Steel is widely used in different industrial fields because of its mechanical and corrosion properties. However, the tendency to corrosion in presence of halide ions limits its applications. One strategy to improve the corrosion resistance is the use of coatings with the incorporation of corrosion inhibitors. Cr (VI) compounds, mainly chromates, are among the most common substances used, and their high efficiency/cost ratio has made them standard corrosion inhibitors. Chromates have been applied in different ways: incorporated into conversion coatings, as an additive in anodising baths and as pigment in painting primers. However, these compounds are highly toxic, and an intense effort is being undertaken to replace them. The aim of this work was to study the influence of the incorporation of cerium ions in silica sol-gel coatings deposited on AISI 304 stainless steel substrates as potential replacement of chromate treatments. This system should combine the “barrier protection” effect of silica coatings with the “corrosion inhibitor” effect of the cerium ions inside the coatings. Silica coatings used as barriers prevent contact between the metal surface and corrosive species. Active protection with cerium would imply that corrosion is inhibited by cerium ions that migrate through the coating to the site of the attack (a defect in the coatings) and then react to passivate the site.