Traditionally, aluminium has been a material that has tended to be welded using a TIG welder. This is due to the fact that MIG welding puts a lot of heat into the metal. This is fine when welding steel, but when welding a metal with a lower melting point, like aluminium, it tends to cause distortion and burn throughs.
The Speed of TIG Welding vs MIG Welding
On the downside, TIG welding is a more complicated process and is significantly slower. These factors have led to the development of Pulsed MIG welding. Pulsed MIG welders use a pulsed current that is turned on when transferring material and turned off immediately afterwards. This gives the weld time to cool and helps prevent you from burning through aluminium. Also, because it's a MIG process, it can take a third of the time to complete a welding job when compared to TIG, which makes Pulsed MIG an attractive proposition for fabricators.
The Price of MIG and TIG Welding
For DIY welders, a pulsed MIG or a TIG welder might be out of their price range. If you have two pieces of aluminium that you'd like to join together and aren't too worried about accidentally wrecking them (for example, if they aren't a visually important section of your car's bodywork), then here's a few tips on how to weld aluminium with a MIG:
- Don't try to weld aluminium that is too thin. A TIG welder can weld aluminium foil - don't expect to be able to do the same with a MIG welder.
- Clean the surface very thoroughly to remove any aluminium oxide. A stainless steel wire brush can be used for this, but don't use one that has been used on steel before, as you may end up contaminating the surface. Also, brush in one direction to avoid rubbing the oxide into the aluminium.
- Use a brass heatsink. Unless you move your welding gun very quickly, which will inevitably make your welding messy, the heat from a MIG welder will blow holes in the aluminium. A brass heatsink that is clamped behind the aluminium will dissipate much of the heat and allow the aluminium to be welded at a reasonable pace. It is advisable to proceed in short bursts, much as you would for thin steel.