The fluxing compounds present in Submerge Arc Welding and Shield metal Arc Welding scavenge and cleanse the molten weld deposit of oxides and gas-forming compounds. Such fluxing slags are not present in GMAW. This place premium on doing a through job of pre weld and inter pass cleaning. This is particularly true for aluminum, where elaborate procedures for chemical cleaning or mechanical removal of metallic oxides, or both, are applied.