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The right MIG welding polarity setting is DCEP (electrode positive) for solid wire with shielding gas, and DCEN (electrode negative) for most self-shielded flux core wire. Gas-shielded flux core wire, stainless wire and aluminum wire also run on DCEP.
Polarity is set by which lead goes on which terminal inside the welder, so it doesn’t change on its own when you change wire. Check the label on every new spool, because the wire maker prints the polarity there. This chart covers the common wires in home and shop MIG welding.
MIG Welding Polarity Settings Chart
| Wire type | Example AWS class | Shielding | Polarity | Gun lead goes to | Work clamp goes to |
|---|---|---|---|---|---|
| Solid carbon steel wire | ER70S-6 | C25 or 100% CO2 | DCEP | Positive (+) | Negative (-) |
| Self-shielded flux core | E71T-11, E71T-GS | None | DCEN (most wires) | Negative (-) | Positive (+) |
| Gas-shielded flux core (dual shield) | E71T-1C, E71T-1M | CO2 or C25 | DCEP | Positive (+) | Negative (-) |
| Stainless solid wire | ER308L, ER309L | Tri-mix or 98/2 argon mixes | DCEP | Positive (+) | Negative (-) |
| Aluminum wire | ER4043, ER5356 | 100% argon | DCEP | Positive (+) | Negative (-) |
Start with the polarity printed on your wire spool or the maker’s data sheet, then use this chart to set the leads.
How to Read This Chart
DCEP means direct current, electrode positive: the wire (through the gun) is the positive side of the circuit. Older manuals call it reverse polarity. DCEN means electrode negative, also called straight polarity.
The AWS class on the spool label tells you the wire family. The last columns show where each lead goes on the polarity terminals inside the wire compartment.
Why Solid MIG Wire Runs on DCEP
Solid wire with gas runs on DCEP because it gives a stable arc, smooth metal transfer and good penetration into the base metal. On DCEN, solid wire gives an erratic arc, heavy spatter and poor fusion, so the bead sits on top of the plate.
That’s why gas MIG setups on everything from a 120V hobby machine to a 250-amp shop welder call for DCEP before you weld.
Why Most Flux Core Wire Runs on DCEN
Self-shielded flux core wire carries its own shielding inside the wire. Most of these wires, such as the E71T-11 and E71T-GS classes, are made to run on DCEN. Electrode negative puts more of the arc heat into the wire, which melts the wire and its flux quickly and keeps penetration shallower on thin steel.
Run that same wire on DCEP and you’ll usually see heavy spatter, a harsh arc and poor bead shape. Our guide to polarity for self-shielded flux core covers the wire-by-wire details.
A few self-shielded wires are made for DCEP, and gas-shielded (dual shield) flux core runs DCEP. Read the spool label every time.
How to Change Polarity on a MIG Welder
Credit: materialwelding.com
Most hobby MIG welders change polarity with 2 short leads inside the wire compartment. Some larger machines use a switch on the front panel.
- Turn the welder off and unplug it.
- Open the wire compartment door and find the polarity terminals, usually marked + and -.
- Loosen the knobs or nuts on both terminals.
- Swap the gun lead and the work clamp lead. For DCEP, the gun lead goes on + and the work clamp lead on -. For DCEN, reverse them.
- Tighten both connections firmly. A loose terminal heats up and causes an unstable arc.
- Close the door, plug in, and run a test bead on scrap.
When you switch from flux core to solid wire, also change the drive roll (knurled to V-groove), fit the right contact tip and hook up gas.
Signs Your MIG Polarity Is Wrong
| Symptom | Likely polarity mistake | Fix |
|---|---|---|
| Heavy spatter and a harsh, crackling arc with flux core | Flux core wire on DCEP | Switch to DCEN if the spool says DCEN |
| Spatter, poor fusion, bead sitting on top with solid wire | Solid wire on DCEN | Switch to DCEP |
| Wire burns back into the tip often after a wire change | Wrong polarity for the wire | Check the spool label and swap leads |
| Shallow bead with lots of slag trouble on dual shield wire | Gas-shielded flux core on DCEN | Switch to DCEP and check gas flow |
If the polarity is right and the bead still looks bad, check wire speed, voltage and gas flow next.
MIG Polarity for Aluminum and Stainless Steel
Aluminum: MIG welding aluminum uses DCEP with 100% argon. DCEP gives the cleaning action that breaks up the oxide layer. Most home welders feed aluminum with a spool gun.
Stainless steel: stainless solid wire runs on DCEP with a stainless gas mix. Stainless flux core wires list their own polarity on the spool, and most gas-shielded ones are DCEP.
MIG vs Stick and TIG Polarity
Polarity rules change with the process. MIG solid wire is DCEP. Stick depends on the rod (7018 runs DCEP or AC, and 6013 runs AC, DCEP or DCEN). TIG on steel uses DCEN, and TIG on aluminum uses AC.
So a welder that does MIG, stick and TIG may need different lead setups for each process. Check the panel diagram before you switch.
Safety Note
Always unplug the welder before you touch the polarity terminals. The terminals carry welding current, and a loose or half-tightened lead can arc, overheat and melt the terminal block. Keep the work clamp on clean bare metal, and weld with good ventilation, since flux core welding makes more smoke than solid wire.
FAQs
Is MIG Welding DCEP or DCEN?
Gas MIG with solid wire is DCEP, also called reverse polarity. Most self-shielded flux core wire is DCEN. The wire decides the polarity, so check the spool label every time you change wire type. Gas-shielded flux core, stainless and aluminum wires run DCEP.
What Happens If You MIG Weld With the Wrong Polarity?
You get heavy spatter, a harsh unstable arc and poor fusion. Solid wire on DCEN sits on top of the steel. Flux core wire on DCEP spatters badly and can burn back into the tip. The welds look rough and may be weak, so swap the leads and test.
Is Reverse Polarity DCEP or DCEN?
Reverse polarity is DCEP, direct current electrode positive. Straight polarity is DCEN, direct current electrode negative. The old names come from early welding, and most modern manuals and wire labels now print DCEP and DCEN, which are easier to read correctly.
Do I Need to Change Polarity for Flux Core Wire?
Yes, if you’re switching from gas MIG with solid wire to self-shielded flux core. Most self-shielded wires need DCEN, so the gun lead moves to the negative terminal. Check the spool first, since some flux core wires, including gas-shielded types, run on DCEP.
Does Polarity Matter for Aluminum MIG Welding?
Yes. MIG welding aluminum uses DCEP with 100% argon gas. DCEP gives the cleaning action that breaks up the oxide film on aluminum. On DCEN, the oxide stays and the bead won’t wet in, so the weld looks lumpy and fuses poorly.
Final Words
The MIG welding polarity setting comes from the wire. Solid wire, gas-shielded flux core, stainless and aluminum run on DCEP. Most self-shielded flux core runs on DCEN.
Read the spool label, swap the 2 leads inside the door when the wire type changes, and run a test bead before the real weld. If spatter suddenly jumps after a wire change, polarity is the first thing to check.
