Anyone ever had problems welding material that has been cut with a plasma. I'm having problems tig welding outside corners on aluminum that has been cut with a plasma. I file off the edge and then hit it with a stainless brush. When I try to weld it its almost like trying to weld cast aluminum. When I cut it with a band saw or with a disk it welds just fine. Should I grind it smooth after I cut it with the plasma? Any ideas?