Aluminum Is a Different Animal
If you need aluminum welding (a boat repair, a trailer fix, a custom fabrication project) don't assume every welder can do it. Aluminum welding is a specialized skill that many otherwise-excellent welders don't offer.
Why Aluminum Is Harder to Weld
Oxide layer. Aluminum forms an oxide layer that melts at 3,700°F while the base metal melts at 1,200°F. The oxide must be cleaned off or it contaminates the weld.
Thermal conductivity. Aluminum conducts heat 5x faster than steel. Heat dissipates so quickly that the welder must work fast and use higher amperage.
No color change. Steel glows red when it's hot, giving the welder visual feedback. Aluminum doesn't change color: it just suddenly melts. There's no warning.
Porosity. Aluminum is highly susceptible to hydrogen porosity (tiny gas bubbles in the weld) if the metal or filler rod has any moisture contamination.
Warping. Because of thermal expansion, aluminum distorts and warps much more easily than steel during welding.
TIG vs. MIG for Aluminum
TIG (GTAW) is the precision method. Uses a tungsten electrode and AC current. Produces the cleanest, strongest welds. Preferred for:
- Thin material (under 1/4")
- Visible/cosmetic welds
- Critical structural joints
- Boat hulls and marine work
MIG (GMAW) with spool gun is faster but less precise. Uses a spool gun to feed soft aluminum wire without bird-nesting. Preferred for:
- Thicker material (1/4" and up)
- Production work
- Structural fabrication where appearance is secondary
What to Ask Before Hiring
- Do you weld aluminum regularly? Not "can you" but "do you, often."
- What process do you use? TIG for precision, MIG for speed. Make sure it matches your job.
- Can you show examples? A good aluminum welder has portfolio photos. The welds should look like stacked dimes, not bird droppings.
- What filler rod do you use? 4043 for general work, 5356 for structural/marine. The wrong filler rod on the wrong alloy causes cracking.
- Are you certified? AWS D1.2 (Structural Welding Code — Aluminum) certification exists. For critical work, ask for it.
Common Aluminum Welding Jobs
- Boat hull and transom repairs
- Aluminum trailer frame repairs
- Custom truck racks and toolboxes
- Aluminum gate and railing fabrication
- Pontoon boat restoration
- Aluminum dock and marine structure repairs
- Intake manifolds and automotive components