Mig welding aluminum

One thing I learned about welding aluminum using ANY method is that the aluminum must be clean!! Not just buffed off but CLEAN. Any oil, paint, oxides, etc can contaminate the weld at best yielding and ugly weld; at worst, no fusion. We even had grinders, wire wheels, and other such tools that were designated "AL" only. After a year or so of trying to maintain a "clean" aluminum area in a usually steel welding shop, the weld techs and engineers figured that it was the iron oxides floating around in the shop that was causing quality issues in spite of our efforts to keep rust contamination away from the aluminum area and had to set up a shop in a separate building for aluminum product only.