Characterization of Cr-α-Al2O3 Composite Coatings Electrodeposited from Cr(III) Plating Bath

Cr-alpha-Al2O3 composite coatings were prepared by direct current deposition experiments from Cr(III) plating bath and the thickness of composite coatings could be up to 14 mu m. The obtained Cr-alpha-Al2O3 coatings and Cr coatings were characterized by means of EDS, SEM and microhardness measurement. Results revealed that Cr-alpha-Al2O3 coatings exhibit fine-grained structure with uniform surface and the highest microhardness values(692 HV) when the alpha-Al2O3 content of coatings was 15g/L, although some pores and defects are still present in the coatings. Analysis of Tafel curves indicated that the presence of alpha-Al2O3 in the Cr coatings show better features in the corrosion resistance both in H2SO4 and NaOH solution than those prepared from the bath without alpha-Al2O3.