Investigation of structural evolution and electrochemical behaviour of zirconia thin films on the 316L stainless steel substrate formed via sol–gel process

In this paper, structural evolution of zirconia (ZrO2) thin films which are produced by a sol–gel dip coating process on the 316L stainless steel substrates were investigated at different temperatures. Microstructural features and phase transformations of the synthesized thin films were characterized by Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric/differential thermal analysis (TG/DTA), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The FT-IR, TG/DTA and XRD analysis results, in a good agreement, indicated that the adopted production route led to the formation of a surface tetragonal zirconia (t-ZrO2) film with high crystallinity at 700 °C. The formed tetragonal phase was transformed to monoclinic zirconia phase (m-ZrO2) at 900 °C. Corrosion performance of the heat treated ZrO2 films was evaluated through potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in 1-M H2SO4 solution at 80 °C. The results demonstrated that the treated thin film at 500 °C had the strongest corrosion barrier performance on the 316L stainless steel. The SEM images showed a crack-free uniform film with an average thickness of 155 nm on the surface can be obtained. Moreover, AFM investigations also showed that the average roughness of the coated films increased with the rising heat temperature.

Research highlights
► Zirconia thin films synthesizes via a sol-gel process.
► Roughness and corrosion manner changes, according to their heat treatment history.
► Measurement the thickness of zirconia thin film by SEM.