Features of passivation of galvanized steel with alkylphosphonic acids and octyltriethoxysilane

In the present work, the influence of the solvent nature in alkylphosphonic acid (CnPs) solutions, the structure of their molecules, namely the hydrocarbon radical length, on the protective and hydrophobic properties of thin films formed on the galvanized steel surface with different morphologies, including those formed by sequential passivation with octyltriethoxysilane (OTES), was studied. It was found that passivation of galvanized steel in ethanol solutions of dodecylphosphonic acid and OTES is more effective than in aqueous solutions of sodium dodecylphosphonate, both when applied alone and in layer-by-layer passivation together with OTES. The inhibiting ability of CnPs with nC=12 and 16 towards galvanized steel enhances with the increase of the hydrocarbon radical length. This regularity is observed both when using C12P and C16P separately and together with OTES. Pre-modification of galvanized steel surface by laser enhances protective and hydrophobic properties of thin films formed in CnPs and OTES solutions. Layer-by-layer treatment of galvanized steel in ethanol solutions of C16P and OTES with a laser surface pre-treatment is most effective for protection of galvanized steel from corrosion in various corrosive atmospheres, namely high humidity with condensation of moisture on the metal surface, in salt spray and in industrial-urban atmosphere.