Investigation of the Effect of Electrolyte on Microstructure and Morphology of the Plasma Electrolytic Oxidation Coatings on Ti

  The porous ceramic layers of TiO2 were synthesized on Titanium through Plasma Electrolytic Oxidation (PEO) process, using three different electrolytes including hydroxide-based, acetate-based, and phosphate-based solutions. The effects of utilizing different electrolytes on the phase arrangement and microstructural characteristics of the ceramic coatings were then studied using X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results showed that utilizing a KOH-based electrolyte can lead to a heterogeneous structure while the layer that is formed during the PEO process in the acetate-based electrolyte can provide large homogeneous pores in the matrix of rutile-TiO2 and CaTiO3 phases. Using the phosphate-based electrolyte could cause an optimum porous layer consists of anatase-TiO2. The results of cross-section of the samples showed that utilizing the acetate-based electrolyte can lead to formation of the PEO coating including two sublayers. The formation mechanism and microstructural outcome of using phosphate-based electrolyte were finally discussed and graphically illustrated.