Abstract:Worldwide trends and requirements from end-users to reduce carbon footprint increases demand on higher recycled content in new products. This can be challenging for aluminium products requiring high surface quality. New developments in scrap sorting technologies opens a possibility for strict control of chemistry of the alloys based on post-consumer scrap. However, despite the available advanced sorting technologies, one might expect that trace element levels in recycled materials will slightly increase.

As the increased concentration of these elements does not deteriorate mechanical properties of the final product, the areas of concern are mainly corrosion and anodizing quality. To develop technical expertise in this area few research projects were performed over the last few years. We will present studies on the alloy development, focusing on the effect of Cu and Zn in the alloy on surface appearance of anodized products. During normal alkaline etching prior to anodizing, one can experience that some grains are etched deeper than others, called “preferential grain etching” (PGE). The effect of Zn, Cu and Mn concentration in 6060 alloy as well as temper on PGE were studied in detail. In addition, the effect of chemistry of the etching bath will be discussed.