Corrosion resistance in artificial saliva of titanium anodized by plasma electrolytic oxidation in Na3PO4

• The anodizing of Ti consists of two steps: a classical one followed by a micro-arc one.
• The inner layer growth is mainly controlled by a classical anodizing mechanism.
• The corrosion resistance enhancement is fully due to the inner layer properties.

In order to improve the chemical and electrochemical resistance of titanium as well as its potential bioactivity, coatings were formed by using plasma electrolytic oxidation under galvanostatic conditions in a phosphate containing electrolyte. The grown anodized layers were characterized at different stages of the oxidation process, corresponding to different voltages. The structure and composition of the coatings were investigated by XRD, SEM-EDS and μ-Raman spectroscopy. The electrochemical behaviour of the coated materials was evaluated in acidified artificial saliva by using classical stationary methods and electrochemical impedance spectroscopy. Before the initiation of sparks, an inner layer is formed by a classical anodizing mechanism. This layer plays the role of barrier, improving the corrosion resistance of titanium in artificial saliva. As soon as the sparking phenomenon starts, a more compact overlayer grows. Due to the presence of large cracks, the corrosion resistance is no more improved.