Effect of Concentration and Voltage on the Corrosion Resistance of Commercially Pure Titanium Plasma Electrolyte Oxidation-coated in Mixed Electrolyte System

Titanium and its alloys are ideal for applications with high levels of reliable performance due to its high strength, low weight ratio, and outstanding corrosion resistance. However, titanium’s corrosion resistance depends on the thin oxide layer naturally forming on the surface, which can easily be damaged and subsequently reduce its corrosion resistance. Plasma electrolytic oxidation is an electrochemical technique that can create protective coatings on metals. The synthesized coatings can provide high hardness, excellent corrosion resistance, and wear resistance. Voltage and electrolyte parameters are some of the factors that can affect coating properties. In this study, the voltage and electrolyte concentration of a mixed electrolyte (aluminate, phosphate, and silicate) were varied in the plasma electrolyte oxidation of commercially pure titanium. The morphology, thickness, composition, and corrosion resistance of the synthesized coatings were characterized by scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffractometer, potentiodynamic polarization, and electrochemical impedance spectroscopy. The electrolyte concentration and voltage affect the coating composition, morphology, and thickness. These properties affect the corrosion resistance. Lower electrolyte concentration increased the effect of aluminate and silicate on the coating morphology and composition. Low concentration settings produced looser and more porous coatings with high Al2TiO5 content. Increasing the voltage increases the rutile-to-anatase ratio and the coating thickness. Overall, the thicker and denser coating, and high rutile to anatase ratio exhibited the best corrosion resistance. The high electrolyte concentration and high voltage settings produced the most corrosion-resistant coating.