Aluminum — What It Is and Why It Matters
Aluminum is a lightweight, corrosion-resistant metal widely used in aerospace, automotive, marine, and consumer products. Welding aluminum presents unique challenges compared to steel: it has a tenacious oxide layer with a melting point (3,700°F) far above the base metal (1,220°F), high thermal conductivity that pulls heat away from the weld quickly, and no color change to indicate temperature.
The oxide layer must be removed mechanically (stainless steel brush dedicated to aluminum) or electrically (AC polarity in TIG welding provides an oxide-cleaning action during the electrode-positive half-cycle). Common welded alloys include 6061-T6 (structural), 5052 (sheet metal, marine), and 3003 (general purpose).
TIG welding with AC output and pure argon shielding is the most common process for aluminum. MIG with a spool gun or push-pull system works well for production and heavier sections. Filler metals ER4043 and ER5356 cover the vast majority of aluminum welding applications.
Frequently Asked Questions
Why is aluminum so hard to weld?
Several factors make aluminum challenging: a high-melting oxide layer that must be cleaned, high thermal conductivity requiring more heat input, no visual color change as temperature rises, a narrow window between melting and burn-through on thin material, and susceptibility to porosity from hydrogen contamination.
Can you MIG weld aluminum?
Yes, using a spool gun or push-pull system to feed the soft aluminum wire reliably, pure argon shielding gas, and a machine capable of spray transfer at the required voltage and wire speed. MIG aluminum is faster than TIG for thicker sections but produces a less refined bead appearance.