AC amperage, balance, tungsten and gas by thickness
Aluminium behaves very differently to steel under a TIG torch — it conducts heat away fast, needs AC output to break up its oxide layer, and punishes bad settings with a dirty, sooty-looking weld. Getting the balance and amperage right for the thickness in front of you matters more here than with almost any other material.
| Thickness | Tungsten | Filler | Amperage | Gas |
|---|---|---|---|---|
| Up to 1.6mm | 1.6mm Pure/Zirconiated, AC | ER4043, 1.6-2.4mm | 40-70A (60-70% EN) | 100% Argon, 12-15 CFH |
| 1.6-3mm | 2.4mm Pure/Zirconiated, AC | ER4043/ER5356, 2.4mm | 70-120A (60-70% EN) | 100% Argon, 15 CFH |
| 3-6mm | 3.2mm Pure/Zirconiated, AC | ER5356, 2.4-3.2mm | 120-170A (60-70% EN) | 100% Argon, 18-20 CFH |
| 6mm+ | 4mm Pure/Zirconiated, AC | ER5356, 3.2-4mm | 170-220A (60-70% EN) | 100% Argon, 20-25 CFH |
EN balance controls the mix between cleaning (oxide-removal) and penetration — more EN cleans better but adds less heat into the joint. 60-70% EN is a solid starting point for clean, unpainted aluminium; thicker or dirtier material can need slightly more.
Working with mild steel or stainless instead? Get MIG, Stick and plasma settings for all three metals.
Use the parameter calculator →Almost always contamination or gas coverage. Clean with a dedicated stainless brush (never one used on steel) and acetone right before welding, and check your cup size and flow rate are giving full coverage.
Balance is set too far toward penetration (too much EP). Increase the EN percentage so the AC wave spends more time cleaning the oxide layer.
Usually hydrogen from surface contamination (oil, moisture) or inadequate gas shielding. Clean thoroughly, check for hose leaks, and increase flow slightly if welding near any draft.
Aluminium's high thermal conductivity means heat spreads fast — use a smaller tungsten and lower amperage than your instinct suggests for thin sheet, and consider a chill bar behind the joint.
See the full calculator for MIG, Stick and plasma settings on aluminium, mild steel and stainless, or check the MIG mild steel settings guide if you're switching processes.