Effect of electrolyte on surface properties of pure titanium coated by plasma electrolytic oxidation

The present study investigated the surface characteristics of pure titanium subjected to a plasma electrolytic oxidation (PEO) process using two different electrolytes containing either potassium pyrophosphate or potassium triphosphate. For this purpose, a series of PEO coating were carried out at ambient temperature with a current density of 200 mA/cm(2). The surface structures of the oxide films were observed via scanning electron microscopy and the volume fractions of constitutive phases were determined based on X-ray diffraction analysis. The surface roughness of the PEO-coated sample in the electrolyte with potassium pyrophosphate was more complicated than that with potassium triphosphate. The volume fraction of metastable anatase phase in the sample coated with potassium pyrophosphate was relatively higher than that with potassium triphosphate, which was mainly attributed to different electrochemical reactions between the substrate and electrolytes during PEO coating. It was also found that the oxide film coated in the potassium pyrophosphate containing electrolyte showed the easy formation of biomimetic apatite in a simulated body fluid solution. (C) 2011 Elsevier B.V. All rights reserved.