Effect of CoSO 4 on the corrosion performance of Ti6-Al4-V plasma electrolytic oxidation coatings

Abstract

To investigate the impact of CoSO₄ on Ti6-Al4-V titanium alloy plasma electrolytic oxidation coatings and their erosion resistance, plasma electrolytic oxidation was performed in electrolytes with varying CoSO₄ concentrations. Scanning electron microscopy, XRD, XPS, electrochemical workstations, and corrosion testers were used to study the effects of CoSO₄ on the morphology, phase composition, corrosion resistance, and erosion properties of the coatings. Results indicated that increasing CoSO₄ concentration led to higher oxidation voltages, fewer micropores and microcracks, and a more uniform and dense surface. The coatings mainly consisted of Ti, Anatase, Rutile, and CoO phases. The best overall performance was achieved with 0.8 g L⁻¹ CoSO₄, where the self-corrosion current density decreased from 1.04 × 10⁻⁷ A cm⁻² (substrate) to 2.21 × 10⁻⁸ A cm⁻², indicating enhanced corrosion resistance.