Anode current effects in plasma electrolytic oxidation

During plasma electrolytic oxidation (PEO) processes, the factors, such as the shape of the specimen, the location of the cathode electrode, and others have a critical influence on the anode (specimen to be treated) current. This may lead to different oxidation dynamics at different locations on the samples resulting in the non-uniform coating thickness and surface properties. In this work, the current through samples made of 2024 aluminum alloy was monitored in a sodium silicate solution during plasma electrolytic oxidation. The experimental results demonstrate that the distance between the cathode and anode affects the anode current and the oxidation efficiency. The current flowing through the front surface (relative to the cathode) of the specimen is larger than that flowing through the back surface of the same specimen. The measured tribological properties and corrosion-resistance agree well with the effects of the current. The front surface exhibits more superior wear and corrosion resistance than the back surface.