Tribological and Electrochemical Corrosion Properties of CNT-Incorporated Plasma Electrolytic Oxidation (PEO) Coatings on AZ80 Magnesium Alloy

Plasma electrolytic oxidation (PEO) coatings were carried out in silicate-based electrolyte embedded with various amounts of carbon nanotube (CNT) additives (0, 0.5, 1, 2 and 4 g/L) on AZ80 magnesium alloy substrate. Microstructure, tribological and electrochemical corrosion properties of the coated specimens were investigated. The results demonstrated that the increasing CNT additions into the electrolyte resulted in a gradual increase in the thickness of PEO-coating layer. The CNT addition to the electrolyte by 0.5 g/L resulted in a slight decrease in the roughness of PEO-coating above which it continually increased. Wear resistance of the PEO-coated specimens showed a gradual improvement with increasing CNT-incorporation within the coating. The electrochemical corrosion tests revealed that the best corrosion resistance was found after the CNT addition into the electrolyte by 0.5 g/L due to the better roughness values, more homogenous coating layers and less pore formation.