Effect of post-treated methods on corrosion resistance of MF-DC magnetron sputtering Al coating on TC4

Purpose This study aims to investigate the effect of post-treatment on anti-corrosion performance of Al coating on the surface of Ti-6Al-4V (TC4) fastener. Design/methodology/approach The Al coatings with different layer structures were prepared on TC4 by middle-frequency and direct-current combined magnetron sputtering. The cross-sectional morphology and surface roughness of coatings were characterized by scanning electron microscope and atomic force microscope. The corrosion resistance was evaluated by electrochemical method. The monolayer coating was post-treated by Alodine chemical conversion, Ar + bombardment and a combination of two methods above. Findings The results show that the interfaces in bilayer and trilayer coatings reduce the defects. Ar + bombardment reduces the corrosion current density, and Alodine chemical conversion leads to a higher pitting corrosion potential. The combined post-treatment has the highest polarization resistance. Originality/value The corrosion resistance of the Al coating is enhanced as the layer quantity increases. The combination of two post-treatments, Ar + bombardment and Alodine chemical conversion, could achieve an overall improvement in corrosion resistance of Al coating.