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Choosing TIG welding current is less about memorizing a single amperage number and more about matching heat to the metal, joint, tungsten, and welding position. Too little current produces a cold, weak weld with poor fusion. Too much current overheats the work, widens the bead, burns through the edge, or contaminates the tungsten. The right setting gives you a controlled puddle that wets both sides of the joint without making you fight the machine.
Starting Current Ranges by Metal Thickness
For a rough starting point, TIG welding mild steel and stainless steel usually requires about 1 amp per 0.001 inch of thickness, or roughly 40 amps per millimeter. Aluminum often needs more heat because it conducts heat quickly, so 1.25 to 1.5 amps per 0.001 inch is a more useful starting range. These are starting points, not rules. Joint design, fit-up, welding position, and the machine’s arc characteristics all change the result.
| Material and thickness | Typical starting current | Useful notes |
|---|---|---|
| Mild steel, 1/16 inch | 45–70 amps | DCEN; use less for a tight lap joint or thin edge |
| Mild steel, 1/8 inch | 90–130 amps | Increase heat for a large fillet or poor heat sinking |
| Stainless steel, 1/16 inch | 35–60 amps | Usually needs less heat than mild steel; avoid overheating |
| Aluminum, 1/16 inch | 60–100 amps | AC; oxide cleaning and preheating affect the setting |
| Aluminum, 1/8 inch | 120–180 amps | AC; use a higher-capacity machine for sustained welds |
These figures assume a reasonably clean joint and a normal travel speed. A thin sheet with a wide gap may need less peak current but more precise control. A heavy plate connected to a large table may need substantially more current because the workpiece pulls heat away from the puddle.
TIG Current for Mild Steel
Mild steel is generally welded with direct current electrode negative, or DCEN. This puts most of the arc heat into the work and gives good penetration. Set the machine to high-frequency start when available, especially on thin material, so you do not scratch-start the tungsten and introduce contamination.
For 1/16-inch steel, start around 55 amps and adjust while watching the puddle. For 1/8-inch steel, 100 to 120 amps is a sensible starting range. Thick plate can require more than 150 amps, particularly for a full-penetration butt joint with a bevel. If the joint is a small fillet, using the maximum available current can simply make the edges undercut.
Use a sharp or lightly truncated 2% lanthanated tungsten, commonly 1/16 inch for low-current work and 3/32 inch for roughly 80 to 180 amps. Argon flow around 15 to 20 cubic feet per hour is typical indoors. Excessive gas flow can create turbulence and actually draw air into the shielding zone.
If the puddle refuses to form, clean mill scale, paint, oil, and rust from both sides of the joint. Increasing amperage is not a substitute for cleaning. A dirty surface can cause porosity, unstable arc behavior, and a gray or sooty bead.
TIG Current for Stainless Steel
Stainless steel is also normally welded on DCEN, but it holds heat poorly compared with mild steel. That means it can become overheated even when the amperage looks modest. Start around 40 to 50 amps for 1/16-inch stainless and 80 to 110 amps for 1/8-inch material. Reduce current or increase travel speed if the weld becomes excessively wide, dark, or sunken.
Heat tint is more than a cosmetic problem. Heavy blue, purple, or black discoloration around the weld indicates oxidation and reduced corrosion resistance. Keep the torch shield over the cooling weld until it stops glowing. A gas lens, clean stainless-only brush, and adequate argon coverage help. For critical or highly visible work, back-purging the inside of tubing prevents sugaring, where the root becomes rough and heavily oxidized.
Pulse can make thin stainless easier to control. For example, a peak current around 50 amps, a background current around 20 amps, and a slow pulse rate can reduce total heat input while maintaining a usable puddle. Pulse is not a cure for poor fit-up or inadequate shielding, but it can reduce warping.
TIG Current for Aluminum and AC Settings
Aluminum requires alternating current because its tenacious oxide layer melts at a much higher temperature than the base metal. AC provides cleaning action on the electrode-positive portion of the cycle while still delivering penetration on electrode negative. Begin with a balance setting near 70 to 75 percent EN, then adjust based on the surface and machine.
For 1/16-inch aluminum, start around 75 amps. For 1/8-inch aluminum, 130 to 160 amps is common. The workpiece should be extremely clean: degrease it first, then use a stainless brush reserved for aluminum. Aluminum often looks cold until the oxide breaks, then suddenly collapses into a puddle. Begin with enough current to establish the puddle quickly and use a foot pedal or fingertip control to back off as the part heats.
Choose an AC/DC TIG welder if aluminum is part of your regular work. A DC-only TIG machine can weld steel and stainless but cannot properly perform the AC cleaning and penetration cycle aluminum needs. Check the machine’s rated duty cycle too: a welder advertised at 200 amps may only sustain that output for part of a ten-minute period.
How to Adjust Current While Welding
Set the amperage slightly low, establish the arc, and increase it until the puddle forms promptly. You want a small, shiny pool that reaches both edges of the joint. If the puddle is sluggish and refuses to tie in, add current or slow your travel. If the edges melt away, the puddle grows uncontrollably, or the bead becomes excessively flat, reduce current or move faster.
Keep a short arc length—about 1/16 inch is a useful target for many jobs. A long arc spreads heat, weakens shielding, and makes the weld wider. Feed filler at the leading edge of the puddle rather than stabbing the tungsten into it. Tungsten contamination can make the arc wander; stop, cut off the contaminated end, and regrind it.
A TIG welding foot pedal is worthwhile for aluminum, thin sheet, and joints that change thickness. It costs more than a fixed-current setup but lets you start hot, reduce heat as the part warms, and handle small gaps without immediately burning through.
Machine Capacity and Protective Equipment
Buy more output than your normal setting if you weld aluminum or thick sections. A 200-amp machine may be adequate for occasional 1/8-inch aluminum, while frequent work on 1/4-inch parts is better served by a 250-amp or larger unit with a healthy duty cycle. For steel and stainless only, a smaller 160-amp DC TIG machine can be the cheaper, sensible choice.
Use a properly rated auto-darkening TIG welding helmet with a low-amperage TIG sensitivity setting. TIG arcs can be dim and difficult for a basic helmet to detect reliably. Wear flame-resistant clothing, welding gloves, and adequate ventilation; stainless fumes and shielding gas require particular care in enclosed spaces.
Make final adjustments from the puddle, not from a chart alone. Charts get you close, but the joint’s fit, mass, cleanliness, and position determine the amperage that actually produces a sound weld.