Clean aluminum pieces more thoroughly. Aluminum reacts more readily with oxygen than steel and it's therefore more important to ensure that there are no contaminants on the surface of the metal. Hydrocarbons from dirt and oil can form aluminum oxide, which will weaken the weld.
Use argon as the shielding gas for aluminum. Aluminum should almost always be welded with 100 percent pure argon, since argon does not react with other elements. The shielding gas for steel typically includes a small amount of carbon dioxide to achieve the desired weld penetration.
Select aluminum electrodes. Aluminum is a much softer metal than steel so the electrodes must be thicker to keep them bending while they are being fed through the welding gun. Aluminum electrodes will generally have a composition that's similar to the base metal.
Use drive rolls that are designed specifically for aluminum. In the case of consumable electrodes, the drive roll delivers the electrodes through the welding gun. Drive roll tension is a much more critical factor for aluminum and it must be set high enough to provide even feeding but low enough so that it doesn't deform the electrode.
Push the weld, rather than pulling it. You should push the welding gun away from the weld puddle to avoid overheating the metal. Aluminum welding should be performed more quickly than steel welding.