An investigation of the characteristics of Al2O3/TiO2 PEO nanocomposite coating

Plasma electrolytic oxidation (PEO) was employed to obtain Al2O3/TiO2 nano-composite coatings. The process was carried out in a silicate base electrolyte in the presence of 0-4 g L-1 TiO2 nanoparticles. ADC power supply was used to apply 150 mA cm(-2) current density for 60 min on aluminum samples. XRD analysis on the coated samples revealed that gamma-alumina and Mullite were formed in all cases, while TiO2 detected just by the incorporation of TiO2 nanoparticles. Surface and cross-section elemental maps of composite coatings implied that the nanoparticles were uniformly distributed in coatings upper parts. Coatings possessed about 25 and 10% porosity in the absence and presence of nanoparticles, respectively. This showed that the denser coating was formed in the presence of nanoparticles. Electrochemical measurements also revealed that adding nanoparticles increased the corrosion resistance of the coatings by decreasing the corrosion current density to about 3 times. Nano-indentation test results showed the increase of Hardness, Young's modulus, Stiffness and Fracture toughness of Al2O3/TiO2 nano-composite coatings. (C) 2015 Elsevier B.V. All rights reserved.