The degree of purity of an aluminum casting alloy is one of important selection criterias. With the increasing purity of a casting alloy family, the corrosion resistance and ductility of the casting parts also increase; the selection of pure ingot for making casting alloys, however, will cause the costs to rise.
Due to the high purity, casting alloys made from primary Aluminum display the best corrosion resistance as well as high ductility. For example, Silumin-Beta with max. 0.15 % Fe, max. 0.03 % Cu and max. 0.07 % Zn can be mentioned.
In many countries, the Silumin trademark has already become a synonym for Aluminum- silicon casting alloys.
Casting alloys made from scrap are, with regard to ductility and corrosion resistance, inferior to other casting alloy groups due to their lower purity.
So it is important to control the ingot purity before casting in order to get the good casting parts.