TIG Welding AC vs DC: Which Do You Need?

What AC and DC mean on a TIG title

TIG welder titles name the current type the machine outputs. AC and DC are two kinds of electrical current, and a TIG machine can be built to output one or both. A listing titled "AC/DC TIG" states both; a listing titled "DC TIG" states one. The word pair is the first thing to read when you compare welder listings on stated details.

The distinction is not cosmetic. The metals a TIG machine is intended for follow from the current type, which is why the title word matters before you decide what to buy. The titles below show the words you will meet and what each one states.

Neither current type is "better" in general. AC is tied to aluminum; DC is tied to steel, stainless and most other alloys. The right machine is the one whose title matches the metal you plan to weld.

• "AC/DC TIG": the machine outputs both current types
• "DC TIG": the machine outputs only DC
• "TIG" alone: the current type is not stated on the title
• "Stick and DC TIG": one machine for DC TIG and stick welding

AC: the setting for aluminum

Aluminum is the metal you will see paired with AC on TIG titles. Aluminum forms an oxide layer on its surface, and that layer behaves differently from the metal underneath it. AC alternates the direction of the current, and a TIG machine that outputs AC uses that alternating action to address the oxide layer. This is why aluminum is the metal tied to AC on a welder title.

As an example, the YesWelder TIG-200P ACDC PRO listing is described as an AC/DC TIG welder for aluminum and thin-gauge fabrication, and Weldpro describes TIG as a process widely used for various metals, especially non-ferrous metals such as stainless steel, aluminum, and copper. If aluminum is in your plans, the machine requirement is an AC/DC TIG listing. A title that names only DC does not state the AC output used for aluminum. See aluminum welding and the best welder for aluminum.

DC: the setting for steel and stainless

DC is the setting for steel, stainless steel and most other alloys. The current flows in one direction, and TIG listings that name only DC are aimed at steel and stainless work. A DC TIG machine is often combined with stick welding in the same listing, which is why you will see titles such as "stick and DC TIG welder".

The Forney X-Series 100 STx is described as a 120V stick and DC TIG welder, and the Forney X-Series 160 STx as a dual-voltage stick and DC TIG welder. The YesWelder TIG-205P PRO is described as a DC pulse TIG and stick welder for steel and stainless welds. If steel and stainless are what you plan to weld, a DC TIG listing can be enough. The TIG versus stick comparison for beginners and the best TIG welders guide both work through this choice.

• "DC TIG" alone: steel and stainless are the stated scope
• "Stick and DC TIG": a combined machine, DC for TIG, stick for its own electrodes
• "DC pulse TIG": DC output with a pulse feature named on the title

Machine requirements: AC/DC versus DC TIG

The machine requirement is what the title states. An AC/DC TIG machine outputs both current types and switches between them. A DC TIG machine outputs only DC, which is why the title names only DC. The words on the title are the maker's statement of what the machine is built to output.

AC/DC TIG appears across the multiprocess category. The Miller Multimatic 220 AC/DC is described as an AC/DC TIG, MIG, flux-cored and stick welder with 120V or 240V input power. The Everlast PowerTIG 185 Micro is titled an AC/DC TIG inverter welder. Compare that with a machine that names only DC TIG: the Miller Multimatic 255 is described as a 208-575 V multiprocess welder with MIG, DC TIG, stick, and flux-cored capabilities. That title does not state AC output.

So the buying question is simple: does aluminum appear in your plans? If yes, an AC/DC TIG machine is the requirement. If no, a DC TIG machine, often paired with stick, can be enough. For a single machine that covers several processes, see multi-process welders and the best multi-process welders guide. Read the maker's specification sheet and manual for any machine you consider; the manual names the supply the machine requires, and local rules apply where you use it.

Reading the title words before you buy

On a TIG listing, the words right before "TIG" tell you the current type: "AC/DC TIG" means both, "DC TIG" means one. Some titles add other process words, such as "stick" or "pulse", next to the current type. A title that says only "TIG" without AC or DC leaves the current type unstated, so the maker's specification sheet is the next place to read.

Multi-process titles can name several processes at once, and the current type applies only to the TIG part. A title such as "AC/DC TIG, MIG, flux-cored and stick" names AC/DC for TIG only; the MIG and flux-core parts run on their own output circuits.

Input voltage is a separate question. A title can name 120V, 240V, or both, and that tells you about the supply the machine is built for, not about the current type it outputs. Compare 120V welders and dual voltage welders on stated details when the input question matters to you, and read welder voltage input for the full explanation.

What to pick for your situation

Questions

Is AC or DC better for TIG welding?

Neither is better overall. AC is the setting used for aluminum, and DC is the setting used for steel, stainless steel and most alloys. Choose the machine by the metal you plan to weld.

Can a DC TIG welder weld aluminum?

A title that names only DC TIG does not state AC output, and AC is the setting used for aluminum. If aluminum is in your plans, look for an AC/DC TIG listing.

What does AC/DC on a TIG title mean?

It means the machine outputs both current types. The Miller Multimatic 220 AC/DC, the Everlast PowerTIG 185 Micro and the YesWelder TIG-200P ACDC PRO are examples of listings that name AC/DC TIG.

What metals does DC TIG cover?

Steel and stainless steel are the metals paired with DC on TIG titles, as in the Forney 100 STx and 160 STx and the YesWelder TIG-205P PRO.

Do I need AC if I only weld steel?

No. DC TIG listings are aimed at steel and stainless work. AC is the setting used for aluminum, so a DC-only machine can be enough for steel.

Is every multiprocess welder AC/DC?

No. Some multiprocess listings state AC/DC TIG, like the Miller Multimatic 220 AC/DC, and others state only DC TIG, like the Miller Multimatic 255. Read the title and the maker's specification sheet.

What should I read before buying an AC/DC TIG welder?

Read the title for the current type, then the maker's specification sheet and manual for the machine's supply requirements. The manual is where the maker states what the machine needs, and local rules apply where you use it.