One of several advantages of gas shielded arc welding of aluminum alloys over other methods of fusion welding is that the need for flux is eliminated, thus removing a potential source of corrosion. Other advantages are that welding can be accomplished in all positions; there is better visibility and greater speed. Sound, pressure-tight joints with high strength and low distortion can be produced. Because of these advantages, the inert-gas-shielded processes are the predominant methods of fusion welding aluminum alloys.
Relatively easy to perform, gas tungsten arc welding (GTAW) uses non-consumable tungsten electrodes, alternating current, and argon or helium shielding gas. When filler material is needed, it can be fed automatically or manually. Aluminum as thin as 0.6 mm (0.025 in.) can be welded, but production welding is more easily controlled when thickness is 1 .O mm (0.040 in.) or greater.
Gas metal arc welding (GMAW), employs aluminum wire as both electrode and filler metal, uses direct current, and a shielding gas of argon or helium, or a mixture of these. The filler wire is fed automatically into the welding zone at a speed compatible with the arc length and welding current, resulting in higher welding speeds than possible with the gas tungsten arc method. Because the heat zone on each side of the weld is narrower, GMAW produces welds of superior strength. A further advantage is that metal of considerable thickness can often be welded without preheating because of high current densities and the concentrated heat of the arc.