TIG on Aluminum Fundamentals: Oxide Management, AC Technique, and Puddle Control

Why Aluminum Feels “Different” in TIG

Aluminum’s surface is covered by an oxide layer (aluminum oxide) that forms immediately in air. This oxide melts at a much higher temperature than the base aluminum, so the arc can appear to “heat” the area while the puddle refuses to open, or it opens unevenly and looks dirty. Aluminum also conducts heat quickly, so the puddle can be slow to start and then suddenly become very fluid once the part warms up. Clean aluminum TIG is largely a process of oxide management, stable AC technique, and puddle control so you can keep the weld zone shiny and responsive.

Oxide Management: Cleaning That Actually Works

Dedicated tools and contamination control

• Use a dedicated stainless steel wire brush that is used only for aluminum. If it has ever touched steel, it can embed contaminants and contribute to porosity and black smut.
• Use dedicated abrasives (Scotch-Brite style pads, flap discs) reserved for aluminum. Cross-contamination is a common cause of “mystery” defects.
• Keep gloves clean. Handling cleaned edges with dirty gloves can reintroduce oils.

Cleaning sequence (practical)

Use a consistent routine so results are repeatable:

1. Degrease first: wipe with a clean lint-free cloth and an appropriate solvent (commonly acetone). This removes oils that would otherwise smear during brushing.
2. Mechanical oxide removal: brush firmly in one direction along the joint area and 1–2 in (25–50 mm) beyond. For thicker oxide, lightly abrade, then brush.
3. Final wipe: a second solvent wipe removes loosened oxide and residue.
4. Weld promptly: aluminum re-oxidizes quickly. Aim to weld within minutes of cleaning, especially on critical joints.

Tip: If you must pause, cover cleaned parts to reduce dust and fingerprints, then do a quick re-brush and wipe before welding.

AC Technique on Aluminum: What the Arc Is Doing

On aluminum, AC is used because it supports two needs at once: maintaining a stable arc for heat input and providing a “cleaning” action that helps disrupt surface oxide at the leading edge of the puddle. In practice, you’ll see this as a clean, shiny puddle that wets smoothly into the base metal when your cleaning, shielding, and technique are working together.

What to look for in the puddle

• Healthy puddle: shiny, reflective surface; edges wet out smoothly; puddle responds predictably to small pedal/hand changes; filler blends without “peppery” contamination.
• Oxide/contamination present: puddle looks dull or “skin-like,” resists opening, has grainy/dirty islands, or forms a crust at the edges.
• Inadequate shielding: surface becomes hazy, gray, or sooty; black deposits appear; arc may sound harsher and puddle becomes less fluid.

Step-by-Step Practice Routine: From First Puddle to Controlled Bead

This routine is designed to build aluminum-specific timing: the delayed puddle start, the sudden fluidity once heat soaks in, and the need to add filler without chilling the puddle.

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Practice setup (repeatable baseline)

• Material: 1/8 in (3 mm) aluminum coupons, clean edges, flat position.
• Joint: start with bead-on-plate, then move to a simple butt joint with a small gap (paper-thin) once puddle control is consistent.
• Filler: choose a common aluminum filler appropriate to your base alloy (for practice, use what your shop standardizes on). Keep rods clean and wiped.
• AC parameters: set to stable, moderate values recommended by your machine for general aluminum. Avoid chasing settings during early practice—change only one variable at a time.

Drill 1: Puddle initiation timing (learning the “delay”)

1. Start on clean plate with the torch steady and your travel hand braced.
2. Hold position without moving and watch for the first true puddle (not just surface shine). Aluminum often takes a moment, then suddenly opens.
3. Count the delay (e.g., “one-one-thousand, two-one-thousand”) so you learn how long your setup takes to form a puddle.
4. Stop and repeat in a new spot. Do 10 starts in a row aiming for the same delay each time.

What you’re training: recognizing when the base metal is actually molten versus just bright from arc light, and preventing the common mistake of moving too early and creating a ropey, cold bead.

Drill 2: Add filler without chilling the puddle

1. Initiate a small puddle and keep it stable.
2. Dip a small amount of filler at the leading edge of the puddle, then immediately withdraw the rod slightly to keep it from overheating and oxidizing.
3. Watch the puddle reaction: if it freezes or becomes lumpy, you’re adding too much filler at once or the puddle is too small.
4. Repeat with smaller dips until the puddle stays fluid and shiny after each addition.

Coaching cue: On aluminum, the puddle can be very fluid once established. Your filler additions should be frequent and small so you don’t “shock cool” the puddle and lose fusion at the toes.

Drill 3: Travel speed to prevent overheating and distortion

1. Run a 3–4 in (75–100 mm) bead with consistent filler rhythm.
2. Focus on forward motion: keep the puddle size consistent rather than letting it grow wider as the plate heats up.
3. As the part warms, increase travel speed slightly and/or reduce heat input to keep the puddle from becoming overly wide and saggy.
4. Stop before the end overheats: aluminum heat soak can make the last inch of a bead look different. Practice stopping and restarting cleanly on a new coupon.

Visual target: a bead that maintains the same width from start to finish, with smooth wetting at the edges and no gray haze.

Defect Diagnosis on Aluminum TIG (Symptoms → Causes → Fixes)

Quick checks when something looks “off”

• If the puddle won’t open: suspect oxide or insufficient cleaning first; verify you’re not moving too soon.
• If it opens but looks dull/dirty: suspect shielding disruption or contamination; re-clean and check torch coverage.
• If it’s shiny but collapses/widens: suspect heat soak and slow travel; increase travel speed and keep puddle size controlled.
• If the arc becomes erratic: suspect tungsten contamination or inconsistent arc length; reset and stabilize your hand position.

Mini-Checklist for Each Aluminum Session

• Degrease → brush with dedicated stainless brush → final wipe → weld promptly.
• Start with stable AC settings and resist constant knob changes.
• Wait for a true puddle; learn your initiation delay.
• Use small, frequent filler additions to avoid chilling.
• Manage heat soak with travel speed and controlled puddle size.
• When defects appear, diagnose from the puddle appearance first, then correct cleaning/shielding/technique before changing multiple settings.