Environmentally-friendly anticorrosive layered zirconia/titania/low-carbon steel structures

Improved corrosion protection of low-carbon steel was achieved by barrier non-toxic sol–gel multilayered structures composed of a ZrO2 top coating and TiO2 underlayers. The zirconium precursor solution was maintained as constant, whereas the TiO2 solution composition was modified with two different types of polymers, which were added separately to the starting titanium solution. The phase composition, morphology and corrosion protective properties were analyzed by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Hydrophobicity properties were evaluated by measuring the contact angle with a Rame-Hart automated goniometer. The potentiodynamic polarization technique was used to determine the corrosion resistance and protective ability of the coatings in a 5% NaCl solution. Both polymeric modifications, as compared to the non-modified titania layer, demonstrated positive effects on the corrosion properties of the structures at conditions of external polarization. Due to the amorphous structure of the zirconia layer and its relatively dense, hydrophobic surface, all of the samples extended the service life of low-carbon steel in a model corrosion medium. The feasibility of the sol–gel deposition method makes it possible to prepare oxide coatings with appropriate surface properties, which ensures high corrosion resistance.