The effect of zinc oxide coating morphology on corrosion performance of Ti-6Al-4 V alloys

•Increasing temperature and potential enhanced thickness and roughness of ZnO layer.•Porosity of ZnO layer was depending on coating morphology and hydrogen evolution.•Spherical and worm-like ZnO morphologies provided the higher corrosion performance.•The higher roughness of ZnO coating resulted the lower corrosion performance.•Different wettability was obtained by various morphologies of ZnO coatings. The release of aluminum and vanadium is one of the major issues affecting the service life of permanent orthopedic devices made of Ti6Al4V. This study aims to improve the corrosion resistance of Ti6Al4V using electrodeposited zinc oxide coatings. Moreover, the effects of bath temperature and applied potential on the morphology, roughness, porosity, wettability, and corrosion performance of zinc oxide coatings were evaluated. The results showed that by controlling the process parameters, zinc oxide coatings with various morphologies including spherical, worm-like, irregular porous network and flower-like were created. The coating changed the hydrophilic nature of Ti6Al4V substrate (wettability of ~46°) to a hydrophobic one. The wettability of the zinc oxide films varied from ~83° for the spherical to ~67° for the flower-like morphology. The long-term corrosion performance of the zinc oxide coatings was estimated in phosphate-buffered saline solution using electrochemical impedance spectroscopy. The results revealed that the spherical morphology provides higher corrosion performance at the initial stage of immersion, however, the corrosion behavior of both spherical and worm-like morphologies became the same after 4 weeks. On the other hand, zinc oxide coating with an irregular porous network of nanoflakes and flower-like morphologies reduced the corrosion performance of Ti6Al4V substrate.