By Susan Kristoff, Updated Mar 24, 2022
Aluminum alloys pose a unique challenge compared to steel. Their lower melting point and higher thermal conductivity can cause burnthrough, especially in thin sheets. Additionally, the softer feeder wire can tangle in the machine.
For most aluminum work, TIG (Tungsten Inert Gas) welding is the method of choice. TIG delivers precise heat control, essential for preventing overheating and burnthrough. It can handle both thin sheets and thick plates. Since TIG uses a separate filler rod, selecting a rod that matches the alloy of the base metal is crucial for a strong, clean joint.
MIG (Metal Inert Gas) welding works well on aluminum, especially when using a spray‑arc or pulse technique. Pulse welding requires an inverter power supply, while spray‑arc can be performed with constant‑current or constant‑voltage machines. MIG is best suited to thinner gauges because it generates more heat. For optimal results, use 100% argon as the shielding gas and choose a filler wire alloy that closely matches the base material.
A gas‑fed torch can weld aluminum, but it demands a high level of skill. Precise heat control is harder to achieve, increasing the risk of burnthrough. Torch welding is best reserved for experienced welders who can manage the torch and filler rod with confidence.
Regardless of the welding method, a clean surface is paramount. Aluminum oxide has a significantly higher melting point than the base metal; any remaining oxides become inclusions that weaken the weld and mar its appearance. Workpieces should be cleaned either chemically (etching) or mechanically (wire brushing) before welding.
