In this study, the influence of different coatings and filter materials on the removal of iron from secondary aluminum-silicon alloys was investigated. Based on three chemical compositions with different initial contents of iron (≈1.2 and 2.0 wt% Fe), manganese (≈0.35 and 1.2 wt% Mn) and chromium (≈0.05 and 1.2 wt% Cr), a two-stepped procedure consisting of (1) conditioning in order to bond Fe in primary Fe-containing intermetallic particles and (2) metal melt filtration using a laboratory filtration apparatus to remove these particles was applied.^[1] Four ceramic foam filter (CFF), consisting of aluminum oxide (Al₂O₃), Al₂O₃ with a coating of Disperal (AlOOH), carbon-bonded (C) Al₂O₃ filter, and C-bonded Al₂O₃ with MgAlON coating, were tested.^{[2, 3]}

For determining interaction effects between the Fe-containing intermetallics and the filter materials, the overall microstructure after filtration was analyzed by optical light microscopy. Scanning electron microscopy (SEM) with energy dispersive spectroscopy was performed to obtain the elemental distribution on the filter cake and the filter interior. Electron backscatter diffraction was conducted for phase identification of Fe-rich intermetallics at the filters interfaces. Whereas the intermetallic β-phase preferentially attached to the dispersal-coated filter surfaces, a favorable adhesion effect was revealed for intermetallic α-phase at the interfaces of the C-bonded Al₂O₃ and MgAlON coated filters. The Fe content was reduced by about 80% due to the multi-functional filter coatings.