AC vs. DC TIG Welding: When to Use Each Polarity
When to use AC vs DC TIG welding explained. How AC cleaning action works on aluminum, DC electrode negative for steel and stainless, and balance and frequency control.
TIG Welding Guide — Settings, Technique & Filler Selection
Complete TIG welding guide: amperage charts by material and thickness, tungsten selection, filler rod guide, AC vs DC settings, gas lens setup, and positional technique.
TIG welding (GTAW, Gas Tungsten Arc Welding) uses a non-consumable tungsten electrode, argon shielding gas, and filler rod added by hand. It produces the highest quality welds of any manual arc process, but it’s the slowest and demands the most skill. TIG is required for aerospace, food-grade stainless, thin-wall tubing, titanium, chromoly, and any application where weld appearance and X-ray quality are non-negotiable.
How TIG Works
The tungsten electrode creates an arc that melts the base metal. You feed filler rod into the leading edge of the weld pool with your other hand. A foot pedal or fingertip control on the torch regulates amperage in real time, giving you precise heat control that no other manual process can match. Argon gas flows through the torch cup to shield the tungsten and weld pool from oxygen and nitrogen contamination.
AC vs. DC TIG
TIG runs in two polarity modes, and the choice depends entirely on the metal:
- DCEN (DC electrode negative) — Steel, stainless, chromoly, titanium, copper, and most metals. The electrode stays cool, and the arc concentrates heat into the workpiece. This is the standard polarity for 90% of TIG work.
- AC (alternating current) — Aluminum and magnesium. The EP (electrode positive) half-cycle breaks up the oxide layer on the surface. The EN half-cycle provides penetration. AC balance control lets you adjust the ratio, typically 65-75% EN for a good compromise between cleaning and penetration.
What TIG Welds Best
TIG welds every commercial metal: mild steel, stainless steel, aluminum, chromoly (4130), titanium, copper, nickel alloys, and magnesium. It excels on thin material, from 0.020" shim stock up to about 3/16". Beyond 3/16", TIG is still used for root passes on pipe and critical joints, but fill and cap passes switch to MIG, stick, or flux-cored for speed.
Tungsten selection matters. Use 2% lanthanated (blue band) as a general-purpose electrode for both AC and DC. Size the tungsten to the amperage: 1/16" for 15-90A, 3/32" for 50-180A, 1/8" for 100-250A.
Filler Rod Basics
Match filler to the base metal. ER70S-2 or ER70S-6 for mild steel. ER308L for 304 stainless. ER316L for 316 stainless. ER4043 for general aluminum. ER5356 for structural aluminum and anodized parts. Always store filler clean and dry.
Articles in This Section
The guides below cover amperage settings, tungsten selection, filler rod compatibility, cup and gas lens setups, walking the cup technique, and troubleshooting. Pick a topic based on what you’re working on.
All Articles
Back Purging Stainless TIG Welds: Setup, Flow Rates & Oxygen Thresholds
How to back purge stainless steel TIG welds with purge dams, argon flow rates, Solar Flux alternative, oxygen thresholds by application, and purge monitoring tips.
Foot Pedal vs. Fingertip TIG Control: Which Amperage Control to Use
Foot pedal vs fingertip TIG torch amperage control comparison. Pros and cons of each, when to use which, torch options, and switching between control methods.
TIG Cup Size Guide: Gas Lens vs. Standard Collet, Cup Sizing & Setup
TIG cup size selection from #4 through #12, gas lens vs standard collet body comparison, jumbo gas lens setups, and gas coverage vs joint access tradeoffs.
TIG Dip Technique: Filler Rod Rhythm, Timing & Coordination
TIG filler rod dipping technique explained. Dab and move cadence, lay wire vs dip method, pulse timing coordination, rod angle, and practice drills for consistent beads.
TIG vs. MIG Welding: When to Use Each Process
Direct comparison of TIG vs MIG welding for speed, quality, cost, ease of learning, and material compatibility. Find out which process fits your project.
TIG Welding 4130 Chromoly: Filler Rod, Preheat & PWHT Guide
How to TIG weld 4130 chromoly steel with ER70S-2 vs ER80S-D2 filler selection, preheat and PWHT requirements, and settings for aircraft and motorsport tubing.
TIG Welding Aluminum Settings: Amperage Chart, AC Balance & Filler Selection
TIG aluminum amperage chart by thickness, AC balance and frequency settings, 4043 vs 5356 filler selection, and argon flow rates for clean aluminum welds.
TIG Welding Copper: Preheat, Amperage Settings & Filler Selection
How to TIG weld copper and copper alloys with preheat requirements, high amperage settings, deoxidized copper filler rods, and argon-helium gas recommendations.
TIG Welding Dissimilar Metals: Filler Selection & Joint Strategies
How to TIG weld dissimilar metals including steel to stainless, copper to steel, and nickel alloy intermediaries. Filler rod selection and joint preparation for mixed-metal joints.
TIG Welding Filler Rod Guide: Types, Sizing & Selection by Base Metal
TIG filler rod selection guide covering ER70S-2, ER70S-6, ER80S-D2, ER308L, ER4043, ER5356. Rod diameter sizing, when to weld autogenous, and matching filler to base metal.
TIG Welding Pipe: Root Pass Technique, Keyhole Method & Purge Setup
TIG root pass on pipe with open root technique, keyhole method, 2G/5G/6G position welding, filler rod manipulation, and purge setup for quality root passes.
TIG Welding Positions: Flat, Horizontal, Vertical & Overhead Technique
TIG welding technique for all positions: flat, horizontal, vertical up and down, and overhead. Torch angles, amperage adjustments, and filler technique per position.
TIG Welding Stainless Steel: Settings, Filler Rods & Heat Control
TIG stainless steel settings by thickness, ER308L vs ER309L filler rod selection, back purging basics, and heat control to prevent sugaring and carbide precipitation.
TIG Welding Steel Settings: Amperage Chart, Filler Rod & Gas Setup
TIG mild steel and carbon steel settings chart with amperage by thickness, DCEN polarity setup, ER70S-2 vs ER70S-6 filler selection, and argon gas flow rates.
TIG Welding Thin Tubing: Heat Control, Pulse Settings & Fixturing
How to TIG weld thin wall tubing for roll cages, exhaust, and frames. Covers heat control, pulse TIG settings, tack sequence, fixturing, and fit-up for tube joints.
TIG Welding Titanium: Purge Chambers, Trailing Shields & Color Guide
How to TIG weld titanium with argon purge chambers, trailing shields, proper gas purity, weld color quality chart, and settings for CP and alloy titanium.
Tungsten Electrode Guide: Types, Color Codes, Grinding & Amperage Charts
Complete tungsten electrode guide with color codes for ceriated, lanthanated, thoriated, and pure tungsten. Grinding angles, diameter selection by amperage, and tip preparation.
Walking the Cup: TIG Technique for Pipe and Structural Welds
Walking the cup TIG technique explained step by step. Cup size selection, when to walk vs freehand, pipe welding applications, and practice drills for beginners.