Welding & Cutting on Painted or Coated Surfaces SWMS

Welding and thermal cutting on painted or coated steel generates a complex chemical fume plume that varies dramatically with the coating system involved. Lead-based paints on older structural steel release respirable lead oxide fume, while epoxy coatings decompose into isocyanates and aldehydes, zinc-rich primers produce zinc oxide causing metal fume fever, and polyurethane finishes liberate hydrogen cyanide and toluene diisocyanate when heated above 200°C. Under WHS Regulation 2025 Part 4.1, any hot work on coated substrates constitutes hazardous chemical exposure requiring atmospheric monitoring, exposure standard compliance, and documented controls. A SWMS is mandatory because the work involves welding fume (now a confirmed Group 1 carcinogen), potential lead exposure triggering health monitoring obligations, and confined airborne contaminant generation that routinely exceeds workplace exposure standards without engineered extraction. This SWMS defines coating identification protocols, stripping requirements, ventilation specifications, and biological monitoring triggers for fabricators, boilermakers, and demolition welders working on existing painted structures.

Hazards identified

7 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Elimination — Mechanically strip coatings 100mm minimum either side of the weld line using needle guns or grinding with HEPA-extracted shrouds before any hot work commences.
2. 2Elimination — Reject hot work on unidentified coatings until XRF lead testing and SDS verification of all coating layers is documented and signed off by the supervisor.
3. 3Substitution — Replace oxy-fuel cutting with cold cutting methods (saw, hydraulic shear, water jet) wherever structural geometry and access permit to eliminate thermal decomposition.
4. 4Substitution — Where stripping is impossible, substitute MIG/MAG with TIG processes to reduce fume generation rate and use lower amperage parameters within procedure tolerance.
5. 5Engineering — Deploy on-torch fume extraction (minimum 100 m³/hr capture velocity) connected to HEPA and activated carbon filtration meeting AS/NZS 60335.2.69 capture efficiency requirements.
6. 6Engineering — Establish local exhaust ventilation with capture hood within 300mm of arc, supplemented by general dilution ventilation achieving minimum 6 air changes per hour in enclosed areas.
7. 7Administrative — Conduct atmospheric monitoring per AS 3640 for lead and AS 3853 for welding fume, with results compared to workplace exposure standards and recorded for 30 years.
8. 8Administrative — Implement biological monitoring (blood lead) at commencement and 3-monthly intervals where lead coatings are present, per WHS Regulation Schedule 14 health monitoring requirements.
9. 9PPE — Issue powered air-purifying respirators with P3 and A2 combination cartridges (minimum APF 50) for all welders, with fit-testing per AS/NZS 1715 documented annually.
10. 10PPE — Provide disposable Type 5/6 coveralls, nitrile inner gloves under welding gauntlets, and dedicated change/decontamination facilities to prevent take-home lead contamination of family members.

Applicable Codes of Practice

Worked example

On a regional water authority project involving structural modifications to a 1970s elevated steel water tower, the lead welder pulls out this SWMS at the 6:30 am pre-start brief beside the work platform. The crew first walks through the hazard register, confirming XRF testing the previous day identified lead chromate primer and an overcoat of polyurethane finish at the cut line. The supervisor allocates roles: one welder will needle-gun strip a 150mm exclusion zone using a HEPA-shrouded tool, while a second worker tents the area with fire-resistant blankets and positions the on-torch extraction unit. Each worker initials the sign-on sheet acknowledging the PAPR requirements and confirms their fit-test currency. During the task at 10:15 am, the atmospheric monitor alarms when wind shifts reduce capture efficiency at the LEV hood. The welder stops work, the supervisor retrieves the SWMS, and the crew applies the documented adjustment protocol — repositioning the extraction arm within 200mm of the arc, increasing extraction flow, and adding a portable axial fan for dilution. The change is noted on the SWMS amendment log, workers re-sign acknowledging the modified control, and work resumes. At shift end, decontamination occurs in the documented sequence: coveralls bagged for disposal, boots wiped, hand and face wash before any food or drink, in line with the take-home contamination control referenced in the controls section.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• AS 1674 — Safety in welding; Welding Fume CoP

Frequently asked questions