Welding Galvanized Steel Safety: Zinc Fume Exposure and Metal Fume Fever

Welding galvanized steel produces zinc oxide fumes that cause metal fume fever, a flu-like illness that hits 4-12 hours after exposure. The condition is usually self-limiting, resolving within 24-48 hours, but repeated unprotected exposure causes cumulative respiratory damage. Every experienced welder knows someone who’s had “galvy flu.” The smart ones only get it once before they start taking precautions.

The galvanized coating is 98% zinc. When the welding arc or cutting torch vaporizes it, the zinc oxidizes in the air and forms a dense white fume. This fume is the problem. Breathing it triggers an inflammatory response in the lungs that produces the characteristic fever and aching.

How Galvanizing Creates Hazards

Galvanized steel has a zinc coating applied by hot-dip immersion or electroplating. The coating thickness varies:

Heavy hot-dip structural galvanizing produces the most fume because it has the thickest coating. Thin electrogalvanized sheet produces less fume but still requires precautions.

When the arc hits galvanized steel, the zinc vaporizes at 1,665F (907C), well below the steel’s melting point of 2,750F (1,510C). This means the zinc boils off ahead of the weld puddle, producing the dense white fume cloud that’s characteristic of galvanized welding.

Metal Fume Fever: Symptoms and Recovery

Symptom Timeline

Important Notes on Metal Fume Fever

It mimics the flu. Many welders don’t connect their symptoms to zinc exposure, especially if the welding was hours earlier. If you develop flu-like symptoms within 12 hours of welding galvanized steel, zinc fumes are the likely cause.

Tolerance develops during the work week but disappears over weekends. Welders who work with galvanized steel regularly may feel fine Monday through Friday but get symptoms on Monday morning after a weekend off. This “Monday morning fever” pattern is characteristic.

It’s usually self-limiting. Most cases resolve without medical treatment. Rest, fluids, and OTC pain relievers for the aches. However, if symptoms include severe shortness of breath, confusion, or persist beyond 48 hours, seek medical attention. Heavy exposure can cause chemical pneumonitis.

Chronic effects: Repeated unprotected exposure to zinc fumes may contribute to chronic respiratory problems. Long-term studies show increased rates of bronchitis and reduced lung function in workers chronically exposed to metal fumes.

OSHA Exposure Limits

Without ventilation, welding galvanized steel easily exceeds these limits. Studies measuring fume concentrations in the welder’s breathing zone during unventilated galvanized welding have found concentrations of 10-50 mg/m3, far above the PEL.

Prevention: The Hierarchy of Controls

1. Elimination: Remove the Zinc Coating

The most effective control is grinding the galvanized coating off before welding. Remove the coating for 2-4 inches on each side of the joint. This eliminates the fume source entirely.

How to grind galvanizing:

• Use a flap disc or grinding wheel rated for zinc/steel
• Remove all coating until bright steel is visible
• Clean the ground area with acetone to remove zinc dust
• Wear a P100 respirator while grinding (zinc dust is also hazardous)

After welding, restore corrosion protection on the exposed area:

• Cold galvanizing compound (zinc-rich paint): spray or brush application, provides 90-95% zinc in the dry film
• Zinc-rich primer: Brush or spray, good for small areas
• Hot-dip re-galvanizing: For complete re-coating (requires sending the assembly to a galvanizer)

2. Engineering Controls: Ventilation

When grinding before welding isn’t practical (large areas, thin sheet, or galvanizing must remain intact):

Local exhaust ventilation (LEV): Position a capture hood 12-18 inches from the arc. The extraction should pull fumes away from your breathing zone. Minimum capture velocity of 100 FPM at the weld point.

General ventilation: In open shop environments, ensure at least 2,000 CFM per welder of general airflow. This helps but may not reduce exposure below the PEL by itself.

Outdoor welding: Natural ventilation outdoors significantly reduces exposure, but position yourself upwind of the fume plume. Don’t assume outdoor air movement is sufficient in calm conditions.

3. Respiratory Protection

When engineering controls alone can’t keep exposure below the PEL:

Half-face APR with P100 filters: Assigned Protection Factor (APF) of 10. Reduces exposure by 10x. Adequate for most galvanized welding situations when combined with ventilation.

PAPR with P100 filters: APF of 25-1000 depending on design. More comfortable for extended work because it supplies filtered air under positive pressure. No breathing resistance.

Supplied air respirator: Required in confined spaces or when exposure exceeds 10x the PEL (50 mg/m3).

4. Work Practices

Keep your head out of the plume. Position yourself so the fume rises away from your face. Use fans or airflow to direct the plume away from your breathing zone.

Weld with the lowest effective heat input. Lower amperage produces less fume. If you can make an acceptable weld at a lower setting, do it.

Use shorter weld runs with breaks. Intermittent welding with cooling breaks reduces total fume exposure per shift compared to continuous welding.

Don’t eat, drink, or smoke in the welding area. Zinc particles settle on surfaces and can be ingested. Wash hands before eating.

Welding Parameters for Galvanized Steel

Beyond the safety considerations, galvanized coatings affect weld quality:

Porosity: Zinc vapor gets trapped in the solidifying weld, creating porosity. Slower travel speed or a slight weave helps gas escape. Some porosity is unavoidable without grinding the coating.

Spatter: Galvanized surfaces produce more spatter. Anti-spatter spray on surrounding surfaces helps cleanup.

Process selection:

• GMAW (MIG): Works well, use slightly higher voltage and slower travel to burn through zinc
• FCAW: Good penetration through the coating
• SMAW: E6013 and E7018 both work, E6013 produces less fume
• GTAW: Not recommended on galvanized surfaces without removing the zinc first; the contamination ruins the tungsten and the weld quality

Filler metal: Silicon bronze (ERCuSi-A) for MIG brazing produces far less zinc fume than fusion welding because the lower process temperature (below zinc’s boiling point) keeps the coating mostly intact. The joint strength is lower than a fusion weld, but for thin galvanized sheet where strength requirements are modest, it’s a good option that dramatically reduces fume exposure.

What to Do If You Get Metal Fume Fever

1. Stop working and move to fresh air immediately
2. Remove contaminated clothing
3. Rest, drink plenty of fluids
4. Take ibuprofen or acetaminophen for fever and aches
5. Monitor symptoms. If shortness of breath is severe, seek medical attention
6. Report the exposure to your supervisor for documentation
7. Review what went wrong. Was ventilation inadequate? Were you positioned in the plume? Did you skip grinding the coating?

Metal fume fever from zinc is uncomfortable but rarely dangerous for healthy individuals. The bigger concern is the welding habits that caused the exposure. If you got metal fume fever, your controls weren’t adequate, and the next exposure to a more dangerous fume (chromium, cadmium) with the same poor controls could have far worse consequences.

Treat every case of galvy flu as a warning sign that your fume control needs improvement. Fix the root cause so it doesn’t happen again.

MIG Brazing as an Alternative

For thin galvanized sheet metal (22-16 gauge), MIG brazing with silicon bronze wire (ERCuSi-A) is an increasingly popular alternative to fusion welding. The process runs at lower temperatures than conventional MIG welding, which keeps most of the zinc coating intact.

How it works: Silicon bronze wire melts at approximately 1,800F (980C), well below steel’s melting point of 2,750F (1,510C) and closer to zinc’s boiling point. The base metal doesn’t melt; the bronze wets the surface and bonds through capillary action and diffusion, similar to brazing.

Advantages for galvanized work:

• Dramatically reduced zinc fume (the coating doesn’t boil off as aggressively)
• Less distortion (lower heat input)
• Better corrosion resistance at the joint (bronze is inherently corrosion-resistant)
• Clean appearance with minimal spatter
• Less post-weld cleanup

Limitations:

• Joint strength is lower than fusion welding (adequate for sheet metal, not for structural)
• Not suitable for thick material or high-load applications
• Requires 100% argon shielding gas (not the standard 75/25 mix)
• Wire cost is higher than carbon steel wire

Settings: 0.030 or 0.035 inch ERCuSi-A wire, 100% argon at 25-30 CFH, voltage 16-20V, wire feed 200-350 IPM depending on material thickness.

MIG brazing on galvanized steel is standard practice in European automotive manufacturing and is gaining acceptance in U.S. fabrication shops. For any application where the joint doesn’t need to carry heavy structural loads, it’s the best way to join galvanized material while minimizing zinc fume exposure and preserving the corrosion-protective coating.

Employer Responsibilities

Employers have specific obligations when workers weld galvanized steel:

• Hazard assessment: Identify when and where galvanized welding occurs and evaluate fume exposure levels
• Engineering controls: Provide adequate ventilation (general and/or local exhaust) as the primary control method
• Respiratory protection: Provide appropriate respirators when ventilation alone can’t control exposure below the PEL, along with a written respiratory protection program
• Training: Inform workers about zinc fume hazards, symptoms of metal fume fever, and proper use of controls and PPE
• Medical surveillance: Not specifically required for zinc oxide exposure, but good practice for workers who regularly weld galvanized materials

If your employer expects you to weld galvanized steel without ventilation or respiratory protection, that’s an OSHA violation. You have the right to request proper controls and to file a complaint with OSHA if the employer refuses.