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 by ZrO₂ top coating and TiO₂ underlayers. Zirconium precursor solution was maintained constant, whereas, the content of TiO₂ solutions was varied. The phase composition, morphology and corrosion protective properties were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectroscopy (XRD) and atomic force microscopy (AFM). Hydrophobicity properties were evaluated by the measuring of the contact angle with Ramé-Hart automated goniometer. Potentiodynamic polarization technique was used to determine the corrosion resistance and protective ability of the coatings in a 5% NaCl solution. Two different types of polymers were added to titanium solution in order to study the effect of TiO₂ surface on the corrosion behaviour of multilayered structures. The polymer modification as compared to the non-modified titania layer has positive effect on the corrosion properties of the structures. Due to relatively dense surface morphology, amorphous structure of zirconia layer and low crystallized TiO₂ coating, all of the samples extend service life of low carbon steel in model corrosion medium. The feasibility of the sol gel deposition method make possible to prepare oxide coatings with appropriate dense surface, which ensure high corrosion resistance.