I know that there is an aluminum type welding rod that is claimed that you can weld and repair with a propane or mapp gas torch. I've never tried it so I can't truthfully comment on how well it works. But one property of aluminum that makes it, as some welders say "difficult", is that it gives little to no clue as to when it's at the proper temperature to be welded. One minute you may be heating up a crack and the next, you are looking at a silver dollar sized hole where the crack used to be and wondering what the £?@× just happened?  And as with welding any metal, oxygen contamination is a real issue. For this reason, I prefer TIG welding aluminum because of the shielding gas. And although I have personal preference to the Miller & a few Lincoln welding machines, I cannot stress enough to stay far away from the Harbor Freight crap welding machines.