AC vs DC Stick Welding: Polarity Explained (DCEP, DCEN & AC)

DCEP (electrode positive) produces the deepest penetration and smoothest arc for stick welding. DCEN (electrode negative) reduces penetration and increases deposition rate but works with fewer rod types. AC eliminates arc blow problems, runs on inexpensive machines, and handles most common electrodes except E6010.

The polarity you choose affects penetration depth, arc stability, spatter levels, deposition rate, and which electrodes you can run. Getting polarity right is as important as setting the correct amperage.

How Polarity Works in Stick Welding

In any DC welding circuit, electrons flow from negative to positive. The direction of electron flow determines where the heat concentrates in the arc.

DCEP (Direct Current Electrode Positive)

Also called “reverse polarity” in older terminology. The electrode is connected to the positive (+) terminal. Electrons flow from the workpiece (negative) to the electrode (positive).

Heat distribution: Approximately 70% of arc heat concentrates at the positive terminal (the electrode) and 30% at the negative terminal (the workpiece). But here’s the counterintuitive part: despite more heat at the electrode, DCEP produces deeper penetration. The electron stream bombarding the workpiece creates a digging action that concentrates heating in a small, deep area of the base metal.

Practical effects:

• Deepest penetration of any polarity
• Smoothest, most stable arc
• Lower spatter than AC
• Electrode melts faster (higher electrode consumption)
• Best for most stick welding applications

DCEN (Direct Current Electrode Negative)

Also called “straight polarity” in older terminology. The electrode is connected to the negative (-) terminal. Electrons flow from the electrode to the workpiece.

Heat distribution: More heat concentrates at the workpiece (positive), but the penetration is actually shallower than DCEP. Without the electron bombardment effect, the heat spreads over a wider area of the base metal.

Practical effects:

• Shallower, wider penetration profile
• Faster electrode melt-off rate (higher deposition)
• More spatter than DCEP
• Less stable arc with many rod types
• Only a few common rods are designed for DCEN

AC (Alternating Current)

AC switches polarity 120 times per second (60 Hz). The current alternates between positive and negative, spending half the cycle as DCEP and half as DCEN. Each time the current passes through zero (120 times per second), the arc momentarily extinguishes and must re-ignite.

Heat distribution: Averaged between DCEP and DCEN. Penetration is moderate, between DCEP and DCEN.

Practical effects:

• Moderate penetration (between DCEP and DCEN)
• Arc stability depends on the electrode coating’s ability to re-ignite 120 times per second
• Eliminates arc blow (no sustained magnetic field)
• More spatter than DCEP
• Louder arc (the 60 Hz buzz)
• Runs on simpler, less expensive machines

Which Rods Run on Which Polarity

Not every electrode works on every polarity. The flux coating chemistry determines compatibility:

The key takeaway: E6010 and E7015 require DCEP. Everything else runs on at least two polarities. E6013 is the most flexible, running on all three.

Why E6010 Won’t Run on AC

E6010 uses a sodium-based binder in its cellulosic coating. Sodium has a high ionization potential, meaning it requires more energy to ionize the gas in the arc gap. On DC, the sustained current maintains ionization continuously. On AC, the arc extinguishes 120 times per second, and the sodium-based gas can’t re-ionize fast enough at each zero crossing. The arc sputters and dies.

E6011 solves this by using potassium instead of sodium. Potassium ionizes at lower energy levels, allowing the arc to re-establish quickly through each AC zero crossing. That’s the only fundamental difference between 6010 and 6011.

Penetration Comparison

The polarity you choose changes how deep the arc melts into the base metal:

For most stick welding, you want the deepest penetration possible, which means DCEP. Switch to AC when arc blow forces you to, or when your machine only outputs AC. Use DCEN only for specific applications where shallow penetration is an advantage (thin material, surfacing overlays).

Arc Blow: The DC Problem AC Solves

Arc blow is the deflection of the welding arc by magnetic fields in the workpiece. It only occurs with DC because the unidirectional current creates a persistent magnetic field in ferromagnetic materials (steel).

What Causes Arc Blow

When DC flows through the workpiece, it creates a magnetic field around the steel. This field is strongest at the ends of the workpiece, near edges, in corners, and around any existing magnetism in the steel (from crane magnets, magnetic chucks, or simply sitting in the earth’s magnetic field for years).

The arc is a conductor carrying current through a gas. When this current-carrying arc passes through a magnetic field, the field pushes the arc sideways, just like a current-carrying wire experiences force in a magnetic field. The result is the arc wandering, deflecting, or blowing to one side of the joint.

Symptoms of Arc Blow

• Arc deflects to one side despite correct rod angle
• Excessive spatter on one side of the bead
• Undercut on one side, buildup on the other
• Arc feels unstable and “pushes” your hand
• Worst at the ends of joints and near edges of the plate
• Gets worse as you increase amperage

How AC Eliminates Arc Blow

AC reverses direction 120 times per second. The magnetic field reverses with it. Over each full cycle, the magnetic forces cancel out, producing zero net deflection of the arc. Switching from DC to AC stops arc blow immediately.

Other Arc Blow Fixes (When You Must Stay on DC)

1. Move the ground clamp. Place it at the end of the joint you’re welding toward. The arc tends to blow away from the ground connection.
2. Weld toward heavy tack welds. Tack welds at the far end of the joint alter the magnetic field path.
3. Use shorter arc length. A shorter arc is harder for the magnetic field to deflect.
4. Reduce amperage. Lower current produces a weaker magnetic field.
5. Wrap the ground cable around the workpiece. Several wraps of the ground cable around the steel create a counter-magnetic field that partially cancels the arc blow.
6. Demagnetize the workpiece. Use a demagnetizing coil on heavily magnetized steel before welding.

When to Use Each Polarity

Use DCEP When:

• Running E6010 (it’s your only option)
• Maximum penetration is needed (root passes, pipe, thick plate)
• Best bead quality and lowest spatter are priorities
• Your machine outputs DC and arc blow isn’t a problem
• Running 7018 on structural work (DCEP is preferred over AC for 7018)

Use AC When:

• Arc blow is deflecting the DC arc
• Your machine is AC-only (older transformer-based “buzz boxes”)
• You’re welding magnetized steel
• Budget limits you to an AC machine
• You’re in a position where arc blow is unavoidable (near edges, in corners, at joint ends)

Use DCEN When:

• You need to reduce penetration on thin material
• Running hardfacing or surfacing overlays where you want minimal dilution with the base metal
• Using specific electrodes designed for DCEN (E6012)
• Build-up work where deposition rate matters more than penetration

AC Machine Considerations

Open Circuit Voltage (OCV)

AC welding requires higher OCV to maintain arc stability. The arc must re-ignite 120 times per second, and adequate voltage is needed to jump the gap each time. Most AC stick welders produce 60-80V OCV. Machines with less than 50V OCV struggle with AC arc stability, especially on rods like E7018.

Transformer vs Inverter AC

Older transformer-based AC welders produce a simple sine wave output. The arc stability is adequate for most rods but can be rough with 7018 and 6011.

Modern inverter welders that offer AC output often modify the AC waveform (square wave AC or high-frequency AC) to improve arc stability. Some allow you to adjust the AC frequency and balance. These machines run AC rods much more smoothly than traditional transformers.

AC Safety Consideration

AC at welding voltages (20-80V) is more dangerous than DC at the same voltage. AC causes muscle contraction at lower voltages and is more likely to cause the “can’t let go” phenomenon. In wet environments, DC is safer. Follow electrical safety practices: dry gloves, insulated work surfaces, and proper grounding.

Polarity and Weld Quality

The relationship between polarity and final weld quality extends beyond penetration:

Spatter: DCEP produces the least spatter. AC produces moderate spatter. DCEN produces the most spatter with most rod types.

Bead appearance: DCEP produces the smoothest, most uniform bead. AC beads are slightly rougher due to the pulsating arc. DCEN beads vary by rod type.

Slag removal: Polarity affects slag behavior. On 7018 at DCEP, the slag self-peels on a good weld. On AC, the slag is slightly more adherent and may require more chipping.

Mechanical properties: For most structural electrodes, the weld’s mechanical properties (tensile strength, impact toughness) are essentially the same on DCEP or AC. The AWS classification tests are performed on the rod’s rated polarity, so following the manufacturer’s recommendation ensures the properties match the datasheet.

Troubleshooting Polarity Issues

Arc is unstable and sputters on DC: Check that your leads are on the correct terminals. DCEP = electrode to positive, ground to negative. Reversed polarity on 6010 or 7018 causes an unstable arc.

Rod sticks constantly on AC: OCV may be too low. Check your machine’s specifications. Some small AC welders can’t deliver enough OCV for reliable arc initiation with 7018. Also verify the rod is AC-rated.

Porosity on one polarity but not the other: Some rods perform better on their preferred polarity. If you’re getting porosity with 7018 on AC, try switching to DCEP. The more stable arc produces better gas shielding.

Arc wanders to one side on DC: Arc blow. Switch to AC, move your ground clamp, or try one of the other arc blow mitigation techniques listed above.

Can’t tell if machine is AC or DC: Check the output terminals. DC machines label them + and - (or DCEP and DCEN). AC-only machines have two identical terminals (sometimes labeled “electrode” and “work”). Multiprocess machines have a polarity switch or selector.

6010 won’t run on your machine: Your machine is AC-only, or it’s a DC inverter that doesn’t produce the specific output characteristics 6010 needs. Some low-cost DC inverters can’t run 6010 because their output doesn’t match the voltage-amperage curve that 6010’s cellulosic coating requires. Check the manufacturer’s specifications.