Electroplating Fumes
Industry & Process · Industry & Process overview
Electroplating fumes are the airborne acid mists, alkaline aerosols and reactive gases released across UK plating shops — from chromic acid plating and sulphuric anodising to nickel, copper, zinc and decorative chrome lines. The dominant hazard is the strong inorganic acid mist liberated by gassing electrolysis at heated open tanks, and exposure is controlled under the Control of Substances Hazardous to Health (COSHH) Regulations 2002 against the Workplace Exposure Limits in HSE EH40.
Where electroplating fumes are generated
Almost every electroplating bath produces a fume above the surface. The mechanism is consistent across processes: current passed through the electrolyte liberates hydrogen at the cathode and oxygen at the anode, the gas bubbles burst at the bath surface, and droplets of the electrolyte are carried into the air above the tank. Heated baths, high current densities, dragout, jigging and rectifier work all increase the rate at which fume reaches the operator's breathing zone.
Different chemistries produce different airborne species and require different controls. Chromic acid plating releases chromium VI mist, sulphuric anodising releases sulphuric acid mist, nickel plating releases nickel-bearing acid mist, and cyanide plating releases hydrogen cyanide if the bath chemistry drops below pH 10.
- Hard and decorative chrome plating — chromium VI as chromic acid mist.
- Sulphuric acid anodising of aluminium — sulphuric acid mist.
- Nickel, copper, tin and zinc plating — substance-specific acid mists.
- Acid pickling, activation and desmut tanks ahead of plating.
- Alkaline cleaning and electrolytic alkaline tanks — caustic aerosol.
- Cyanide-based plating — risk of HCN release on pH excursion.
- Stripping, etching and bright-dip tanks.
Why plating fume exposure matters
Chromium VI as chromic acid mist is a recognised Category 1 occupational carcinogen with a very low EH40 limit; sulphuric acid mist sits in the same IARC strong-inorganic-acid-mist group. Nickel-bearing aerosols are respiratory sensitisers and the subject of strict EH40 controls. Cyanide release from pH excursions is acutely toxic. Add the short-term peaks during loading, jigging and rectifier work and the COSHH judgement on a plating shop nearly always relies on quantitative personal sampling against substance-specific WELs.
Plating fume is also corrosive to the building. Visible rusting of roof steel and electrical enclosures above tanks is a reliable engineering indicator that capture is inadequate and that operator exposure warrants re-sampling.
Monitoring electroplating fume exposure
Each bath chemistry is sampled by its substance-specific MDHS-equivalent method. Chromium VI is captured on a treated filter and analysed by a sensitive colorimetric or IC method. Sulphuric, hydrochloric and nitric mists are sampled by ion chromatography of the relevant anion. Nickel and copper aerosols are sampled and analysed by ICP/AAS. Hydrogen cyanide is sampled on a sorbent tube. Personal pumps on the most exposed operator across a full shift drive the COSHH judgement; static and area samples support LEV diagnostics.
Sampling strategy follows BS EN 689 with explicit attention to the short-term EH40 limits during loading, dragout, jigging, rectifier shutdown and tank maintenance.
Controlling electroplating fumes
Control follows the COSHH hierarchy. Where chemistry allows, substitute to lower-hazard processes — trivalent chrome for hex chrome, citric for nitric passivation, alkaline non-cyanide formulations. Where the bath must remain, the engineering controls are well-established: fume suppressants on chrome and decorative chrome baths, plastic ball blankets on hot acid tanks, lip or push-pull LEV sized to the actual bath surface, and packed-tower or venturi scrubbing of discharge.
All LEV in a plating shop is corrosive duty — polypropylene or FRP ducting, acid-rated fans, scrubbed discharge — and is subject to Thorough Examination and Test at least every 14 months under COSHH Reg 9. RPE is the final layer for residual exposure during tank cleaning and breakdown response.
When to review plating fume exposure
Review the COSHH assessment on a change of bath chemistry, current density, temperature, surface area or throughput; following an LEV modification; on changes of supplier or substrate; on operator symptoms or sensitisation reports; after an enforcement or insurer visit; and at a defined two- to three-year refresh. Chromic acid lines warrant shorter sampling intervals and tighter LEV verification than general plating.
Frequently asked questions
Is chromic acid plating still allowed in the UK?
Yes, but under tight controls. Chromium VI use is constrained by UK REACH authorisation, and hex-chrome plating shops must demonstrate substance-specific COSHH controls, low operator exposure and well-maintained acid LEV.
Can a single fume sample cover all baths in a plating shop?
No. Each chemistry has its own EH40 limit and its own sampling method. A plating-shop survey samples each operator against the substances they are actually exposed to across the day.
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