Effect of TiO2 nano-particles on corrosion behavior of Co-Cr alloy coatings in simulated body fluid

Co-Cr and Co-Cr/nano-TiO2 coatings were electrodeposited from Cr(III) based baths. The effect of TiO2 nano-particles incorporation on the morphology, structure, crystallite size, and preferred orientation was studied. Corrosion behavior of the composite coating was also investigated by means of polarization and electrochemical impedance spectroscopy techniques in Hanks’ simulated body fluid, and the results were compared to the unreinforced Co-Cr film. SEM micrographs revealed that the TiO2 nano-particles have been distributed uniformly within the Co-Cr matrix. Co-deposition of these particles insignificantly changed the nodular morphology of the Co-Cr film. Both the coatings had hcp-Co structure with the highest relative texture coefficient (RTC) for the (100) peak. According to the corrosion results, corrosion potential of the Co-Cr/TiO2 was nobler than the Co-Cr film and its corrosion current density was about 0.75 of that for the unreinforced alloy coating. The charge transfer resistance of the Co-Cr coating in Hanks’ solution was increased from 73.6 to 127.9 kΩ cm2 by incorporation of TiO2 nano-particles. However, the double layer capacitance of the Co-Cr film was about 3 times higher than the Co-Cr/TiO2 coating.