Effects of alloy types on the gloss of anodized aluminum

The effects of alloying elements, microstructures and coating thickness on the surface gloss of anodized aluminum panels were investigated. Three automotive aluminum alloys (AA5083, AA5657 and AA6111) were tested. The oxide film growth rates for the three alloys are all in the 0.46 to 0.49 mum/min (18.1 to 19.3 mu-in./min) range. The gloss of anodized AA5657 was the highest, followed by AA6111 and AA5083. For AA5657 and AA6111 alloys, the magnesium contents are about the same, but AA6111 alloy has much higher manganese, silicon and copper content, which contributed to the higher roughness and lower gloss. For AA5083 alloy, the grain size changes during forming did not effect the gloss changes during anodizing.