Welding galvanized steel with standard settings produces porosity, excessive spatter, rough beads, and clouds of white zinc oxide smoke. The zinc coating disrupts every aspect of normal welding because it vaporizes at 1665F, well below the steel’s melting point at 2750F. Zinc vapor erupts through the molten puddle, blows out shielding gas, and contaminates the weld deposit. Adjusting your settings and technique compensates for these effects.
The fundamental approach: give the zinc time and energy to vaporize and escape before the weld puddle solidifies over it. That means slightly higher heat input, slower travel speed, and a technique that pushes zinc vapor ahead of the puddle rather than trapping it underneath.
MIG Welding Galvanized Steel
MIG is the most common process for galvanized steel production work (HVAC ductwork, guardrails, trailers, agricultural equipment). Standard ER70S-6 wire works, but settings need adjustment.
Parameter Adjustments
| Parameter | Normal (Bare Steel) | Galvanized Adjustment | Why |
|---|---|---|---|
| Voltage | Normal for thickness | +1 to 2 volts | Wider puddle, more time for zinc to escape |
| Wire Feed Speed | Normal | Slight increase (5-10%) | Compensates for zinc disruption |
| Travel Speed | Normal | Slower (15-25%) | Allows zinc vapor to escape puddle |
| Stick-out | 3/8" | 1/2" to 5/8" | Slightly lower heat input at wire tip |
| Gun Angle | 5-15 degrees drag | 10-15 degrees push | Pushes zinc vapor ahead of puddle |
| Gas Flow | 20-25 CFH | 25-30 CFH | Compensates for zinc vapor displacement |
MIG Settings by Thickness (Galvanized)
| Material Thickness | Wire (.030" ER70S-6) | Voltage | WFS (IPM) | Gas (75/25) |
|---|---|---|---|---|
| 20 ga (.036") | .023" or .030" | 16-17 | 200-250 | 25 CFH |
| 18 ga (.048") | .030" | 17-19 | 250-300 | 25 CFH |
| 16 ga (.060") | .030" | 18-20 | 280-330 | 25 CFH |
| 14 ga (.075") | .030" | 19-21 | 300-360 | 25 CFH |
| 12 ga (.105") | .030" | 20-22 | 330-390 | 25-30 CFH |
| 10 ga (.135") | .035" | 21-23 | 320-380 | 25-30 CFH |
| 3/16" | .035" | 22-24 | 350-420 | 30 CFH |
Shielding Gas for Galvanized MIG
75/25 argon/CO2 is the standard. It produces cleaner welds than straight CO2 on galvanized because the argon stabilizes the arc against zinc vapor disruption.
Straight CO2 is an alternative. The more turbulent puddle produced by CO2 actually helps zinc vapor escape. The tradeoff is more spatter (which is already worse on galvanized). Some production shops prefer CO2 for its lower cost and deeper penetration on galvanized structural work.
100% argon is required for silicon bronze MIG brazing (see below). Do not use argon/CO2 blends for brazing.
Silicon Bronze MIG Brazing
For light-gauge galvanized (20-14 ga), silicon bronze MIG brazing is often a better option than fusion welding.
ERCuSi-A wire with 100% argon at 25-30 CFH. The silicon bronze melts at approximately 1800F, just barely above zinc’s boiling point (1665F). This minimizes zinc vaporization, dramatically reduces fume, preserves most of the galvanized coating near the joint, and eliminates porosity since the steel base metal doesn’t melt.
| Material Thickness | Wire (.030" ERCuSi-A) | Voltage | WFS (IPM) |
|---|---|---|---|
| 20-18 ga | .030" | 15-17 | 200-280 |
| 18-16 ga | .030" | 17-19 | 250-330 |
| 16-14 ga | .035" | 18-20 | 220-300 |
| 14-12 ga | .035" | 19-21 | 250-340 |
Limitations of silicon bronze brazing:
- Lower joint strength than fusion welding (adequate for sheet gauge, not structural plate)
- The bronze bead is a different color than steel (visible appearance difference)
- Not suitable for material over 12 ga (strength becomes inadequate)
- Not prequalified under AWS structural codes
Stick Welding Galvanized Steel
Stick welding handles galvanized steel well because the forceful arc of cellulosic electrodes (6010, 6011) blasts through the zinc coating and drives zinc vapor out of the puddle.
Electrode Selection
E6010 (DCEP only): The best stick electrode for welding through galvanized coating. Its deep-digging, aggressive arc punches through zinc and produces a weld with minimal porosity. The cellulosic coating generates its own gaseous shield that’s less affected by zinc vapor than external shielding gas.
E6011 (AC or DCEP): Same performance as 6010 for galvanized work but runs on AC machines. If you have a transformer (AC-only) buzz box, 6011 is your rod for galvanized.
E7018: Not ideal for galvanized. The smooth, quiet, low-hydrogen arc doesn’t drive zinc vapor out effectively. The result is porosity and a rough bead. If you must use 7018 (for code or strength requirements), grind the zinc off the joint area first.
E6013: Acceptable for light-gauge galvanized where deep penetration isn’t needed. It’s a compromise between 6011’s performance on zinc and 7018’s bead quality.
| Electrode | Galvanized Performance | Current | Best Application |
|---|---|---|---|
| E6010 | Excellent | DCEP | Structural galvanized, pipe |
| E6011 | Excellent | AC, DCEP | Field work, AC machines |
| E6013 | Good | AC, DCEP, DCEN | Light gauge, general repair |
| E7018 | Poor | AC, DCEP | Only after zinc removal |
Stick Settings for Galvanized
Run 10-15% higher amperage than normal for the electrode diameter. The extra heat helps drive zinc vapor through the puddle and improves bead quality. Use a slightly longer arc length than normal (1.5 electrode diameters instead of 1) to give zinc vapor room to escape.
| Rod Diameter | Normal Amps | Galvanized Amps |
|---|---|---|
| 3/32" E6011 | 40-80A | 50-90A |
| 1/8" E6011 | 75-125A | 85-140A |
| 5/32" E6011 | 110-170A | 125-185A |
Flux-Core Welding Galvanized Steel
Self-shielded flux-core wire (E71T-11) is well-suited for galvanized welding because its self-generated shielding isn’t disrupted by zinc vapor the way external gas shielding is.
E71T-11 produces its own shielding gas from the flux core. Zinc vapor doesn’t displace this shielding the way it interferes with MIG gas coverage. The result is fewer porosity problems than MIG on galvanized, with no external gas to set up.
E71T-1 (gas-shielded) also works on galvanized with similar parameter adjustments to MIG: slightly higher voltage, slower travel speed, push technique.
| Material Thickness | Wire (.035" E71T-11) | Voltage | WFS (IPM) |
|---|---|---|---|
| 16 ga | .035" | 16-18 | 180-220 |
| 14 ga | .035" | 17-19 | 200-250 |
| 12 ga | .035" | 18-20 | 220-280 |
| 10 ga | .035" | 19-21 | 240-300 |
| 3/16" | .045" | 20-23 | 200-260 |
Universal Technique Tips for Galvanized
These tips apply regardless of process:
Push technique (forehand). Push the puddle forward so zinc vaporizes ahead of the molten pool and escapes into the air. Dragging (backhand) traps zinc vapor under the solidifying puddle, causing porosity.
Slower travel speed. Give the zinc time to vaporize and escape before the puddle solidifies over it. If you see heavy porosity, slow down.
Slight weave or oscillation. On MIG and flux-core, a slight side-to-side motion keeps the front of the puddle open longer, allowing zinc vapor to escape. Don’t confuse this with wide weaving on chromoly or stainless where you want minimum heat input. On galvanized, a controlled oscillation helps.
Tack welds. Galvanized tacks are more likely to crack or pop off than bare steel tacks. Make tacks slightly longer and heavier than normal.
Spatter management. Anti-spatter spray on the workpiece and nozzle is more important for galvanized than bare steel. The zinc-contaminated spatter is tenacious and hard to remove once cooled.
Ventilation is mandatory for all processes. Adjusting your settings doesn’t reduce fume exposure. See the galvanized safety guide for ventilation and respiratory protection requirements.
TIG Welding Galvanized Steel
TIG is the least practical process for galvanized steel. The tungsten electrode is extremely sensitive to contamination, and zinc vapor reaching the tungsten degrades it rapidly. The resulting unstable arc makes it nearly impossible to produce consistent beads.
If you must TIG galvanized material:
- Grind all zinc coating off the weld zone first (minimum 1 inch each side)
- Run standard TIG settings for bare steel
- Keep the tungsten pointed away from any remaining zinc residue
- TIG on bare steel after zinc removal produces excellent results, just like bare steel
For practical purposes, if the job requires TIG quality, grind the zinc off and TIG on bare steel. If the zinc can’t be removed, switch to stick with 6010/6011 or flux-core.
Troubleshooting Galvanized Welding Defects
Heavy porosity throughout the bead. Primary cause: zinc vapor trapped in the solidifying puddle. Slow down, push instead of drag, and increase voltage by 1-2 volts to widen the puddle and give gas time to escape. If porosity persists, grind the zinc off the weld zone.
Excessive spatter that won’t come off. Zinc-contaminated spatter bonds aggressively to the workpiece. Apply anti-spatter compound before welding. Consider switching to silicon bronze MIG brazing on thin material, which produces far less spatter.
Rough, uneven bead profile. Caused by zinc vapor disrupting the arc. Run slightly hotter than normal settings and maintain consistent push angle. Accept that galvanized beads won’t look as clean as bare steel beads. If appearance is critical, grind the zinc off first.
Worm tracks (linear porosity on the bead surface). Zinc vapor escaping through the puddle as it solidifies leaves visible tracks on the surface. Slow travel speed and push technique help. On critical welds, grind and re-weld.
Cracking in thin gauge material. The higher heat settings needed for galvanized can cause burn-through and cracking on 20-24 gauge material. Switch to silicon bronze brazing, which runs cooler and preserves the coating.
After welding, the zinc coating is destroyed in the weld zone and HAZ. Restore corrosion protection using the methods in the zinc coating repair guide.