On the real effectiveness of experimental silicon alkoxides based pre-treatment as adhesion promoter for different painted metals

Abstract Silicon alkoxides sol-gel pre-treatments act as coupling agents between metal substrates and organic coatings. This kind of metal finishing is widely studied pre-treatment, but relatively little study is done on the effect of this sol-gel pre-treatment on the durability and on the corrosion protection properties of the complete protection system which consist of a pre-treated and, subsequently, painted metals. In this paper the performance of a sol-gel layer produced from a mixture of silicon alkoxides precursors was applied on different metals (galvanized steel, copper, aluminum) as a pre-treatment prior the application of an organic coating. The effect of the sol-gel pre-treatment on the durability of the painted metals was investigated evaluating the dry and wet adhesion of the organic coating to the substrate as well as the corrosion resistance in the salt spray chamber and the resistance to cathodic delamination. The laboratory testing proved that the experimental sol-gel layer provides the three different painted metals with an improved corrosion resistance, thus leading to a reduced extent of delamination of the coating from the substrate after the accelerated tests.