Corrosion and tribocorrosion protection of AZ31B Mg alloy by a hydrothermally treated PEO/chitosan composite coating

This study is aimed at the enhancement of the corrosion and tribocorrosion performance of AZ31B magnesium (Mg) alloys after plasma electrolytic oxidization (PEO) treatment. Some PEO-treated Mg samples were coated with chitosan (CS) film by dip-coated method, while others were subjected to hydrothermal treatment (HT) followed by CS film. The microstructure and chemical composition of coatings were investigated via X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. Corrosion resistance of the specimens was evaluated via electrochemical measurements (open circuit potential and electrochemical impedance spectroscopy) in simulated body fluid. The tribocorrosion performance was determined by simultaneously recording the variation of the friction coefficient and the open circuit potential with the sliding time. The results indicated that better corrosion and tribocorrosion performance were observed when CS layer is applied on hydrothermally treated PEO samples than on the bare PEO samples. Thus, fabrication of hydrothermally treated PEO surface coatings with chitosan is a significant approach to protect the Mg from corrosion and tribocorrosion, thereby increasing the potential application of Mg alloy as biological implants. •PEO coating with limited barrier properties is formed on AZ31B Mg alloys.•PEO coating is treated by hydrothermal treatment with dip-coated chitosan covering film.•Composite coatings decrease corrosion and tribocorrosion activity of the PEO-coated sample in SBF.•The mechanism of the corrosion and tribocorrosion protection of the composite coatings on Mg sample in SBF is revealed.