Reinforcement of CuZn coatings obtained by electrodeposition from a free-of-cyanide alkaline solution containing Al2O3 hard particles

Abstract

An alkaline free-of-cyanide electrodeposition solution using sorbitol as complexing agent was employed for obtaining metal-matrix-composite coatings of CuZn-Al 2 O 3 . These coatings consisted of CuZn as metal matrix and hard micrometric alumina (Al 2 O 3 ) particles as the dispersed phase. These composite coatings could be employed in protection of metallic pieces subjected to erosion-corrosion, since they will combine corrosion resistance of the CuZn matrix and mechanical resistance given by the hard Al 2 O 3 particles. It is shown that these coatings could be obtained from the proposed solution, but only in high electrodeposition cathodic current densities (i g ), for ½i g ½> 15 mAcm -2 . Vickers microhardness (MH) of the composite coatings was significantly increased when comparing with pure CuZn coatings for i g . The increased microhardness is due to occluded Al 2 O 3 , since it was not observed grain refinement due to Al 2 O 3 . Based on these results, CuZn-Al 2 O 3 composite coatings have prospects for erosion-corrosion protection.