Aluminum Is a Different Animal

Welding aluminum on an engine driven welder is common for trailers, boats,
irrigation pipe, vehicle bodies and repair work—but it behaves nothing like steel. It oxidizes
instantly, conducts heat fast, and loses strength as it heats, so the wrong setup produces a black,
porous, cracked mess. With the right process and settings, however, a field welder makes clean aluminum
joints anywhere there is no shop.

Which Process for Aluminum?

  • MIG with spool gun (most field-friendly): A spool gun feeds 4043 or 5356 wire
    right at the gun, avoiding the bird-nesting and feed problems of long aluminum wire runs. Needs a CV
    output on the engine driven welder.
  • MIG with push-pull gun: Better for long, thin wire; puller at the gun plus feeder in
    the machine keeps feed stable. Higher cost, less common in field kits.
  • TIG (GTAW): Best for thin sheet, cosmetic and code work; AC TIG with high-frequency
    start and balanced/unbalanced control. Slower but precise.
  • Stick (SMAW): Possible with special aluminum electrodes (e.g., E4043) but
    technically difficult and not for structural; limited to non-critical repairs.

Shielding Gas and Wire

  • Gas: 100% argon for TIG; argon or argon/helium mixes for MIG. Never use CO2 or
    steel-gas mixes—they contaminate aluminum.
  • Wire: 4043 for general welding and good fluidity; 5356 for higher strength and
    color match after anodizing. Match wire to base alloy.
  • Wire diameter: 0.8–1.2 mm for most field work; thinner for sheet,
    thicker for heavy plate.

Preparation Is Everything

  • Remove oxide: Aluminum oxide melts at ~2000 °C while the metal melts at
    ~660 °C. Wire-brush only with a stainless brush (steel brushes embed contamination) or
    degrease and lightly abrade just before welding.
  • Degrease: Oil, coolant and cutting fluid cause porosity. Clean with a proper
    solvent.
  • Fit-up: Tight, clean joints; aluminum’s high heat conductivity demands good
    contact to avoid lack of fusion.

Engine Welder Settings and Technique

  • CV mode for MIG: Set wire feed speed and voltage per the chart; aluminum needs
    slightly higher voltage than steel for the same wire.
  • Polarity: MIG is DCEP (electrode positive). TIG is AC.
  • Travel and angle: Push angle (10–15° from vertical) for MIG on
    aluminum; this keeps the shielding gas on the puddle and reduces oxidation.
  • Heat control: Aluminum shows no color change before melting; watch the puddle and
    avoid overheating, which collapses the joint or burns through thin sections.
  • Spool gun setup: Keep the gun cable straight, set proper tension, and purge gas
    before striking to clear air from the line.

Common Aluminum Problems and Fixes

  • Porosity: Contaminated base, oil, or insufficient gas coverage. Clean thoroughly
    and increase flow (18–25 L/min).
  • Lack of fusion: Too cold, wrong angle, or dirty surface. Raise heat, push the
    gun, clean better.
  • Cracked bead: Too much heat input, wrong filler, or restraint. Reduce amps, slow
    travel, use 5356 where appropriate.
  • Black, sooty weld: Wrong gas or gas loss. Confirm argon and check for leaks.

Field Tips

  • Use a wind shield or tent for outdoor MIG; argon is light and easily blown away.
  • Preheat thick sections (>6 mm) slightly to even out heat and reduce cracking.
  • Keep wire dry; aluminum wire absorbs moisture on the surface, causing porosity.
  • Practice on scrap of the same alloy before the real joint.

Conclusion

Aluminum welding on an engine driven welder is very achievable with a spool gun or
AC TIG, clean preparation and correct gas and filler. Master the prep, polarity and push technique and
you can weld trailers, boats and irrigation pipe in the field. Explore our aluminum
welding equipment and consumables to build a capable field kit.

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