Electrochemical assessment of characteristics and corrosion behavior of Zr-containing coatings formed on titanium by plasma electrolytic oxidation

Commercially pure (CP) titanium was treated by plasma electrolytic oxidation in phosphate and zirconate electrolytes. The microdischarge behavior and corrosion properties of plasma electrolytic oxidation coatings containing zirconium on CP-Ti prepared in electrolytes containing various additive concentrations under different duty cycles were studied by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Electrochemical corrosion tests indicated that the PEO coating formed in zirconate solution under an appropriate duty cycle showed a much superior stability during the corrosion tests and provided an efficient corrosion protection. Relationships are drawn between PEO applied duty cycle, electrolyte concentration and corrosion performance. The protective coatings treated at lower duty cycles had higher corrosion resistance during long time immersion in sodium chloride solution due to more compact microstructural features. The EIS analysis of the PEO coating provided information about the evolution of internal structure of the coating with duty cycle of the process.