Material guide
Welding Aluminium: TIG, Spool Guns and the Oxide Problem
Aluminium welding is a cleaning job with welding attached: the oxide melts at 2000°C while the metal underneath melts at 660°C, and the pool gives you no warning before it falls through.
Process and filler selection
Default process: AC TIG for quality, MIG with a spool gun for speed, 1.6 mm+ only. Filler: ER4043 (general) or ER5356 (stronger, better on 5xxx alloys).
Preparation
Stainless brush the oxide layer off right before welding — it reforms within hours. Fit-up matters more than settings: gaps eat filler and heat control at exactly the wrong moment.
Heat management
Oxide melts at ~2000°c while the metal underneath melts at ~660°c — cleaning and ac balance are everything
Two routes: AC TIG vs MIG + spool gun
| Route | Best at | Needs |
|---|---|---|
| AC TIG | thin to ~6 mm, cosmetics | AC/DC machine, argon, ER4043/5356 rod |
| MIG + spool gun | 1.6 mm+ speed work | spool gun, argon, U-groove rolls |
Technique: hotter and faster than you think
Aluminium dumps heat into the job, so you need more amps per millimetre than steel — around 40–55 A/mm on TIG — and faster travel. Push the torch with a 10–15° lead angle. The pool hides under oxide: it looks dull until it's suddenly gone. Brush with a stainless-only brush right before welding; the oxide layer starts reforming within hours.
Frequently asked questions
Can you weld aluminium with a MIG welder?
Yes, with two conditions: the machine supports a spool gun or has an aluminium-capable drive, and you use 100% argon with aluminium wire (ER4043 or ER5356). Soft aluminium wire jams in long conventional MIG torch liners — that's what the spool gun solves. Thickness under ~1.6 mm belongs on TIG.
How to weld mild steel
To weld mild steel: use MIG or stick, gasless flux-core outdoors, filler matched to the parent metal (ER70S-6 MIG wire, E48xx stick rods, ER70S-2 TIG rod), and prepare properly — grind back to bright metal at least 20 mm each side of the joint. The key adjustment vs mild steel: baseline (40 A/mm MIG rule).
What filler wire or rod for mild steel?
For mild steel use ER70S-6 MIG wire, E48xx stick rods, ER70S-2 TIG rod. Matching filler to the parent grade is the rule — mismatched filler either cracks, corrodes or underperforms the base metal.
Best welding process for mild steel?
The best process for mild steel is MIG or stick, gasless flux-core outdoors — chosen for how the metal conducts heat and what contamination costs you.
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