Effect of TiO2 Coating Thickness on the Structure, Mechanical Properties, and Corrosion Behavior of AISI 304L Stainless Steel

TiO2 coatings of various thicknesses (100, 200, and 300 nm) are produced by ultrasonic spray on 304L stainless steel substrates for biomedical applications. The structural, morphological, and mechanical properties of TiO2 coatings were investigated using SEM, x-ray diffraction (XRD), Raman spectroscopy, and nanoindentation tests. Potentiodynamic polarization, electrochemical impedance spectroscopy, and Mott–Schottky analysis were used to study the corrosion performance of the sample in simulated body fluid. The results showed an anatase structure for all coatings with crystallite sizes ranging from 13.6 nm to 36.4 nm. The coating exhibited slightly higher hardness (H) and higher elastic modulus (Y) than those described in the literature for anatase. The results of the corrosion tests showed that the sample with TiO2 coatings deposited at 300 nm is more resistant to corrosion. TiO2 coatings can offer excellent corrosion resistance to 304L steel. The corrosion rate of the coated steel was found to be significantly lower when compared to the substrate, and these coatings had a protection efficiency of 90.3%. TiO2 is an n-type semiconductor, according to Mott–Schottky (M-S) tests.