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AC vs. DC in Welding – What Is It? Difference Explained

AC vs. DC in Welding – What Is It? Difference Explained

These days, more TIG welders are starting to feature AC & DC welding as standard.

But what is it? And what are the differences between them?

While AC & DC are available on most TIG welders, there is a significant difference in how they work and what they’re used for.

AC & DC – What Is It?

 The “A” and “D” stand for “Alternating” and “Direct.” This refers to the type of current the welder uses to create the arc.

AC stands for “Alternating Current”. This is where the electricity flows back and forth, switching polarity rapidly. This is ideal for welding aluminum and magnesium.

DC stands for “Direct Current”. This is where the electricity flows in one direction consistently. DC is further divided into DCEN (Direct Current Electrode Negative) and DCEP (Direct Current Electrode Positive). DCEN is ideal for most metals, while DCEP is used for thick stainless steel.

On TIG welders, the AC & DC feature is crucial for handling different types of metals. TIG welders will still offer both for those who work with various materials.

MIG and stick welders typically only use DC, as it’s better suited for their processes and the metals they commonly weld.

Both these settings give a welder greater flexibility in how they approach different materials.

Although you can find AC and DC settings on several welder models, their effectiveness varies depending on whether you’re using a TIG, MIG, or stick welder.

AC DC
Weld Spatter More Less
Arc Stability Worse Better
Filler Metal Deposition Rates Moderate High
Penetration Moderate High
Voltage Drops Using Long Leads No Yes
Arc Blow Occurs When Welding Magnetized Metal No Yes
Welds Ferrous Metal Like Steel SMAW only All arc welding processes
Welds Aluminum AC TIG DC MIG
TIG Welding Equipment Cost High Low
Stick Welding Equipment Cost Low Medium to High

When Would You Use AC & DC Modes?

Like other tools’ modes, a welder’s AC and DC modes have several advantages, depending on the type of metal you want to work with.

In short, AC is used when welding aluminum and magnesium. The alternating current breaks down the oxide layer on these metals, allowing for better penetration and a cleaner weld. AC’s cleaning action is crucial for these reactive metals.

DC is used for most other metals. DCEN provides deep penetration and is great for steel, stainless steel, and copper. DCEP offers more cleaning action but less penetration, making it suitable for thick stainless steel where oxide removal is needed.

AC Vs. DC In TIG Welding – How It Works

The AC and DC feature on a TIG welder is designed to handle different metals effectively. The choice between AC and DC dramatically affects how the arc behaves and interacts with the metal.

Note: you cannot use AC and DC simultaneously, so you choose based on your workpiece material.

AC In TIG Welding

AC in TIG welding (GTAW welding) is more complex. You set the balance between EN (Electrode Negative) and EP (Electrode Positive) phases. More EN gives deeper penetration, while more EP provides better cleaning.

You also set the frequency—higher for a focused arc and lower for a wider one. This affects bead shape and penetration. Some welders let you adjust the waveform (sine, square, triangular) for even more control.

To use AC, you select it on your machine, adjust settings, and weld. It’s perfect for aluminum, creating beautiful, strong welds.

DC In TIG Welding

Using DC in TIG welding is straightforward. You choose between DCEN and DCEP based on your needs.

DCEN is the go-to for most metals. The electrode’s negative charge makes electrons flow to the workpiece, generating more heat there. This leads to deep, narrow welds—ideal for steel, copper, and thin stainless steel.

DCEP is less common. Here, electrons flow from the workpiece to the electrode, heating it more. This gives shallower penetration but better cleaning, useful for thick, oxidized stainless steel.

You simply select DCEN or DCEP, set your amperage, and weld. No balance or frequency to worry about.

AC Vs. DC In Other Welding – How It Works

In MIG welding, DC is the norm. MIG guns are designed for constant polarity, almost always DCEP. This provides stable arc and good penetration for steel.

Some advanced MIG welders offer AC for aluminum, but it’s rare. Most prefer spool guns or push-pull systems with DCEP for aluminum MIG.

For stick welding, DC dominates. DCEP is standard, as it stabilizes the arc and manages the electrode coating. Some rods like E6011 can use AC for better arc restart and all-position welding.

Interestingly, some stick welders offer DCEN for cellulosic rods (E6010, E6011) on thick steel, providing deeper penetration.

AC Vs. DC – The Core Differences The core differences between AC and DC are the current flow and their effects on different metals:

  • AC alternates polarity, providing both penetration and cleaning. It’s a must for aluminum.
  • DC maintains one polarity. DCEN gives deep, focused welds for most metals. DCEP offers more cleaning for thick, oxidized steel.

AC’s alternating nature suits reactive metals needing oxide removal. DC’s consistency suits metals where steady penetration matters more.

Understanding AC and DC helps you match your welder to your materials. It’s a fundamental feature that defines what you can weld and how well you can weld it. In the world of welding, choosing between AC and DC isn’t just a setting—it’s the key to mastering different metals.

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