The increasing use of recycled materials for the production of aluminum alloys brings many advantages, but also challenges. One of these challenges is the behavior with regard to filiform corrosion of coated secondary AlSi7Mg0,3 casting alloys. Compared to primary alloys, they show poorer performance in filiform corrosion tests. In the present work, results from electrochemical measurements, standardized filiform corrosion tests, energy dispersive X-ray spectroscopy elemental mappings, and scanning Kelvin probe force microscopy studies on variations of secondary AlSi7Mg0,3 casting alloys are presented. In addition, two AW 6016 wrought alloys have been chosen for comparison. The alloys are compared with each other on the basis of chemical composition and resistance to filiform corrosion. They have been investigated to evaluate the influence of the contaminating alloying elements Fe, Cu, Mn and Zn on the tendency to form filiform corrosion.
The results presented show that no secondary casting alloy yet shows comparable resistance to filiform corrosion to the primary alloy. At the same time an increasing content of minor elements from secondary metal production is not necessarily associated with a lower resistance to filiform corrosion.