Cr-α-Al₂O₃ Composite Electrodeposition Technology

The Cr-α-Al2O3 composite coatings were prepared.The effects of Al2O3 concentration,mixing speed and temperature on thickness and Al2O3 content in the coating were studied.The morphology, bonding strength and corrosion resistance of the coating were tested.The results show that the adhesion between coating and substrate was good.With the increase of Al2O3 particle concentration the composite coating thickness and the particle content increased firstly and then decreased.The effect of mixing speed on the thickness was smaller than that of the particle content.The Al2O3 content showed an extreme value when the mixing speed reached 220 r/min. The thickness and Al2O3 content of the composite coating declined with the increase of temperature.Compared with single metallic chromium coating,the cracks of Cr-α-Al2O3 composite coating were finer obviously.The corrosion resistance of Cr-α-Al2O3 coating was the best in the NaCl solution,next in the NaHCO3 and worst in the H2SO4.