ABSTRACT
When a voltage is applied between metallic electrodes immersed in an electrolyte, that is, a solution containing dissolve ions, a variety of electrochemical processes, including the coating of the electrodes, may occur at the electrode–electrolyte interface. A particularly interesting scenario arises when the voltage exceeds a certain critical value, corresponding to the dielectric strength of the coating. When this occurs, the layer is no longer able to insulate the voltage, and tiny electric arcs, so-called microarcs, moving over the electrode surface begin to form. The energy released by the microarcs causes local heating of the substrate fostering several processes including punctual melting of the coating and the substrate. This fused material can react with species in the electrolyte and be redeposited on the substrate. In this way, it is possible to produce chemical, structural, and morphological modifications on the surface of a material without affecting its bulk properties. In this chapter, some fundamentals of this technique, frequently referred to as plasma electrolytic oxidation (PEO), are discussed. To emphasize the versatility of PEO and its ability in improving the performance of biomaterials, results obtained with the treatment of titanium and tantalum are presented.
