[GRX]

I'm a machinist not a welder, but knowing how to weld is an essential part of that trade. Or at least it used to be. Well anyway, maybe I can give you a few pointers.

Did someone mention the Aluminum must be clean? Yes. Think they did! Use a type of Acetone for this. Brake cleaners & the like can give off bad fumes. As well as leave residues. Also, get yourself a stainless brush & use it ONLY for Aluminum.

Pre-heating the Aluminum before welding can be a huge help. Make sure you have a clean oxidizing flame for this.

One important thing to be aware of is that Aluminum has a more narrow melting range than Iron/Steel. In other words, not much a temperature difference between the liquid and gaseous (burning) states. Therefore one cannot as easily rely on watching how the work piece & puddle glow.

Welding Aluminum definitely takes a bit more finesse than Steel. Hats of to the man (or woman) who can lay a perfect row of dime shaped beads with their MIG.

Hope that helps.