Electrodeposition of Bright Al-Zr Alloy Coatings from Dimethylsulfone-Based Baths

Electrodeposition of Al coatings from dimethylsulfone (DMSO2)-AlCl3 baths with the addition of ZrCl4 was studied. Although pure Al coatings electrodeposited from the bath without ZrCl4 are lusterless, bright and smooth coatings were obtained when the ZrCl4 content in the baths was 0.005-0.015 mol per 10 mol DMSO2. The Zr content in the coatings varied up to 3.5 at% in proportion to the ZrCl4 content in the baths. The bright Al-Zr alloy coating showed high reflectance of 50-80% in the wavelength range of 450-1000 nm, whereas that of the matte pure Al coating was 10-20%. Morphological observations confirmed a reduction in the grain size of Al and surface leveling caused by the addition of ZrCl4 to the baths. Moreover, a strong < 100 > preferential orientation of Al crystals was observed for the bright coatings. The bright coating containing similar to 3.5 at% Zr had a higher corrosion potential by 0.1 V than the pure Al coating. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.079204jes] All rights reserved.