Corrosion resistance of the surface layers formed on titanium by plasma electrolytic oxidation and hydrothermal treatment

This study is concerned with the modification of titanium surface by plasma electrolytic oxidation (PEO) and hydrothermal treatment. The samples were oxidized in an electrolytic solution that contained calcium beta-glycerophosphate and calcium acetate. Then, the specimens were hydrothermally heated at a temperature of 220 degrees C for 4 h using an autoclave. The chemical composition of the surface layers was examined by XPS. The morphology of the surface was observed by SEM-EDS. The crystalline phases were identified by XRD. The corrosion resistance was determined by the electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 degrees C after various times of exposure in SBF. The oxide layers formed by PEO were porous, highly crystalline and enriched with Ca and P. After hydrothermal treatment, hydroxyapatite crystals precipitated on the surface. The results of electrochemical examinations show that the surface modification by PEO and hydrothermal treatment decreases the corrosion resistance of titanium. (c) 2005 Elsevier Ltd. All rights reserved.