ABSTRACT
Since the 1930s the ethyl-polysilicates have been used in prehydrolysed forms as binders for zinc-rich paints. They lead to the formation, but only on sand-blasted ferrous substrates, of inorganic coatings that provide a high protection against corrosion. The characterisation, by means of appropriate physico–chemical analytical techniques, of sol gel derived coatings, not zinc-loaded, has led us to propose a process allowing the formation of thick and adherent silica coatings even on polished supports. Despite the adhesion properties of coatings obtained by this process, it appears that they systematically suffer from cracking after ageing. Vibrational analysis by Raman microspectrometry of the starting solutions of the silicates and of their derived coatings has provided evidence of the considerable importance of the effect of the initial sol composition on the evolution of the morphology of the coatings with time.
