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How to Weld Galvanized Steel Safely

Published October 3, 2026 · Built by Jeremy Panasuk

The thickness calculator will print a wire size and an amp window for any number you type. It does not know the steel is galvanized, and it does not sample the air. On zinc-coated steel the first documents are the fume controls. An amp comes after those controls, and only as math for the steel you measured under the coating. It is not a procedure for welding the coating, and it is not a reading in milligrams per cubic meter.

What AWS says the illness is

AWS Safety and Health Fact Sheet No. 25, November 2025, says metal fume fever is caused primarily by exposure to zinc oxide fume. AWS calls it an acute illness many welders meet during their working lives. The sheet says studies indicate the most common cause is overexposure to zinc fumes from welding, cutting, burning, or brazing galvanized steel. Other metals, including copper and magnesium, may cause similar effects. Zinc is also on OSHA’s list of metals that show up in welding fume.

AWS lists the symptoms of overexposure as headache, fever, chills, muscle aches, thirst, nausea, vomiting, chest soreness, fatigue, gastrointestinal pain, weakness, and tiredness. The sheet says symptoms usually start several hours after exposure, that an attack can last 6 to 24 hours, and that complete recovery generally occurs without intervention within 24 to 48 hours. It is more likely after time away from the work, such as a weekend. At the time of a high exposure, AWS describes a metallic or sweet taste, a dry and irritated throat, thirst, and coughing. Several hours later a low-grade fever occurs, seldom higher than 102 °F (39 °C), followed by sweating and chills, with temperature returning to normal in 1 to 4 hours. AWS’s instruction if you encounter these symptoms is to contact a physician and have a medical examination. That instruction is not optional color. OSHA’s separate acute-exposure line is the same direction: workers who get eye, nose, or throat irritation, dizziness, or nausea should leave the area immediately, seek fresh air, and obtain medical attention.

The limit AWS states, and who measures it

AWS Fact Sheet 25 states that the current OSHA standard for zinc oxide fume is 5 milligrams of zinc oxide fume per cubic meter of air, averaged over an eight-hour work shift. The same paragraph states the ACGIH threshold limit value as 2 mg/m³ as a time-weighted average and 10 mg/m³ as a short-term exposure limit. Those two sentences are AWS’s citation of the limits. This page did not sample a shop, and the calculator cannot.

AWS says to use air sampling to tell whether ventilation is adequate. Samples should be taken by a qualified person, in the employee’s breathing zone, using approved methods. The sheet points that method to AWS F1.1. A grinder, a chart, and a guess are not that sample.

Controls, in the agencies’ order

OSHA’s fact sheet on welding fume says welders should understand the hazards of the materials they are working with, and that the Hazard Communication standard requires employers to provide information and training. It says welding surfaces should be cleaned of any coating that could potentially create toxic exposure, such as solvent residue and paint. Cleaning is one control on that list. It is not the whole list, and grinding a stripe does not retire the rest.

OSHA says workers should position themselves to avoid breathing welding fume and gases, and should stay upwind when welding in open or outdoor environments. General ventilation, natural or forced fresh air, can reduce fume and gas levels. The next sentence matters: welding outdoors or in open work spaces does not guarantee adequate ventilation. Where there is no ventilation and exhaust, OSHA says to use natural drafts along with positioning so fume stays away from the welder and from other workers.

Local exhaust is the control that pulls fume out of the breathing zone. OSHA says to keep fume hoods, fume extractor guns, and vacuum nozzles close to the plume, and that portable or flexible exhaust can be aimed so fume is drawn away from the welder. Exhaust ports should be kept away from other workers. OSHA says not to weld in confined spaces without ventilation. Respiratory protection may be required if work practices and ventilation do not reduce exposures to safe levels. Shielding gases such as argon and carbon dioxide can displace oxygen and can lead to suffocation, particularly in a confined or enclosed space.

AWS’s own avoidance list is not softer. Keep your head out of the fumes. Do not breathe fumes. Use enough ventilation, fume extraction at the arc, or both, to keep fumes and gases out of your breathing zone and the general area. If other precautions are not adequate or practical, wear a NIOSH-approved respirator that removes the fumes from your breathing zone. AWS names ANSI Z49.1 and NIOSH Publication No. 78-138 among the references for those precautions. OSHA’s fact sheet says it does not impose new compliance requirements; the standards it points to include 29 CFR 1910 Subpart Q, 1926 Subpart J, 1915 Subpart D, permit-required confined spaces at 1910.146, hazard communication at 1910.1200, respiratory protection at 1910.134, and air contaminants at 1910.1000. Follow those, not a shortened version of them.

Removing a coating is the subject of how to clean metal before welding. That page’s rusty-versus-clean rod switch is a different problem. A zinc coating is a fume source until the controls above are in place. It is not solved by flipping a menu from 7018 to 6011.

Only then: a thickness number, and what it refuses to be

Suppose the steel under the coating measures 62 mils. That is this calculator’s 1/16 inch input. It is not a statement that galvanized sheet comes in a 62-mil gauge, and it is not a coating weight. On the MIG tab, enter 62 and leave shielding on 75/25 argon/CO2. Wire size is .023 inch because 62 is under 78 mils. Amps are 62 times 0.9, divided by 5, rounded, then multiplied by 5: 62 × 0.9 is 55.8, 55.8 ÷ 5 is 11.16, which rounds to 11, and 11 × 5 is 55. The display adds 15 percent and rounds, which is 63, so the line is 55–63 amps. Wire speed uses 3.5 inches per amp for .023 wire: 55 × 3.5 is 192.5, which rounds to 193, and 10 percent more rounds to 212. Gas flow prints as 20–25 cubic feet per hour. The power line says a 120 volt machine is OK, because 62 mils is under the 188-mil step.

That paragraph is the mild-steel short-circuit function doing arithmetic. The function’s own note assumes mild steel. Galvanized steel is coated. Printing .023 inch wire at 55–63 amps does not say the zinc is gone, does not say the breathing zone is under 5 mg/m³, and does not authorize striking an arc on the coating. If the controls in the sections above are not in place, do not use the number. If they are in place and a qualified person has not sampled the air, the number is still only a thickness start for the steel, to be confirmed on scrap that is actually the same condition you will weld. It is not a fume measurement.

A common mistake

The mistake is a bright stripe and a mild-steel chart. Grind until the metal looks silver, open the MIG tab, and weld with your head over the joint because the work is outdoors and the coating “looked gone.” AWS says the most common cause of metal fume fever is overexposure to zinc fumes from welding, cutting, burning, or brazing galvanized steel. OSHA says outdoors does not guarantee adequate ventilation, and that coatings which can create toxic exposure come off as one control among positioning, general ventilation, local exhaust, and a respirator when those are not enough. A ground stripe is not an air sample. The 55–63 amp window does not become safe by being a small number.

Limits, and when to stop

This site cannot tell you the coating weight, whether removal was complete, or what a breathing-zone sample would read. Confined spaces, unknown coatings, and any job that needs a qualified procedure are outside a calculator. If the symptoms AWS lists show up, contact a physician, as that sheet says. If OSHA’s acute symptoms show up, leave, get fresh air, and obtain medical attention. A thickness result after that is still just a thickness result. Machine class for uncoated plate is a different page, 1/4 inch steel, and it does not override this one.

Frequently asked questions

What does AWS say causes metal fume fever?

AWS Fact Sheet 25 says metal fume fever is caused primarily by exposure to zinc oxide fume. It says studies indicate the most common cause is overexposure to zinc fumes from welding, cutting, burning, or brazing galvanized steel. Symptoms include headache, fever, chills, muscle aches, nausea, and chest soreness, and AWS says to contact a physician if you encounter them.

What zinc oxide limit does AWS attribute to OSHA?

AWS states that the current OSHA standard for zinc oxide fume is 5 milligrams per cubic meter of air, averaged over an eight-hour work shift. The same sheet states the ACGIH TLV as 2 mg/m³ as a time-weighted average and 10 mg/m³ as a short-term exposure limit. This page does not measure air.

What does the MIG tab return for 62 mils, and what does that not mean?

If the steel under the coating measures 62 mils, the MIG function returns .023 inch wire at 55–63 amps and 193–212 inches per minute, and it labels a 120 volt machine OK. That is mild-steel thickness math. It is not a galvanized procedure, not a fume reading, and not permission to weld the coating.

Compiled with AI assistance from the sources below. Spot an error? Email [email protected].

Sources