Silane films obtained from silane precursors 3-(trimetoxisililpropil) methacrylate and tetraethoxysilane with cerium ions addition: Influence of the curing process

In galvanized steel, the metal is protected by a zinc layer, but this layer shows poor adhesion to painting systems and low corrosion resistance. A very efficient way of protecting against corrosion is to utilize chromate layers which provide excellent anticorrosive properties and good adhesion, but this strategy is being abandoned since it employs hexavalent chromium which is carcinogenic. An environmentally-friendly alternative is the use of a sol-gel process to obtain organic-inorganic hybrid coatings. These films combine the properties of polymeric and ceramic materials, increasing density, flexibility and functional compatibility with organic systems and contributing to increase the strength and adhesion to the metallic substrate. In this context, galvanized steel was coated with a silane film obtained from a solution consisting of silane precursors 3-(trimethoxysilylpropyl) methacrylate (TMSPMA) and tetraethoxysilane (TEOS) with addition of cerium nitrate (0.01 mol.L(-1)). Different curing process (air, heat and UV) were used. The films were characterized by scanning electron microscopy (SEM), contact angle, open-circuit potential, potentiodynamic polarization, EIS and FTIR. The results showed that the cerium ions promoted coating deposition and did not alter the barrier properties. Besides, the particular curing process used, influenced the barrier effect of the silane film and therefore its corrosion performance.