Effect of alumina particle size on characteristics, corrosion, and tribological behavior of Co/Al2O3 composite coatings

Abstract

The electrodeposition technique was used to produce Co, Co/micro-Al2O3, and Co/nano-Al2O3 coatings. The effect of particle size on current efficiency, thickness, composition, morphology, and structure of the coatings was investigated. The potentiodynamic polarization technique and electrochemical impedance spectroscopy was used to study the corrosion behavior of the coatings. Tribological behavior of the micro/nano-composite coatings was also examined, and the results were compared to the pure Co and the steel substrate. The results revealed that the incorporation of alumina nano-particles decreased the current efficiency of Co electrodeposition. Although the weight percent of the co-deposited nano-particles was much less than the micro-particles under the same electrodeposition conditions, their effect on morphology was more pronounced. The Co/micro-Al2O3 coating had a higher hardness and corrosion resistance than the other samples. The incorporation of nano-particles decreased the hardness and polarization resistance of the pure Co by about 15 and 59%, respectively. Unlike the corrosion results, both the composite coatings had better wear resistance than the pure Co film. However, the volume loss of the Co/micro-Al2O3 coating was 1.6 times lower than the Co/nano-Al2O3 electrodeposit.