Effect of abrasives on the glossiness and reflectance of anodized aluminum alloys

Blasting can eliminate or change the surface texture of as-rolled aluminum alloy by indentation to roughen the alloy's surface. We investigated the effects of the blasting conditions on the glossiness and reflectance of Al1050-H16 and Al5052-H32 alloys in this study. As-rolled sheets were blasted at various pressures, and then removed for sequential cleaning, chemical polishing, and anodizing steps. After each step the samples were measured by micro-TRI-gloss meter and spectrophotometer to compare the effects produced by the abrasive powders and processing variables. Polyhedral alumina and round iron powders were used as the blasting media. The glossiness (Gs(60°)) decreased as the root mean square roughness (Rq) increased, regardless of the shape of the abrasive powders. The abrasives powders could cause wear and/or fracturing during the blasting process as well as fine debris, which could become embedded in the blasted surface. When an aluminum alloy was blasted with iron powders, the glossiness value after alkaline etching and chemical polishing was greater than that after being blasted with alumina; while the anodized Al5052-H32 alloy's surface became more yellowish in color.