| 📋 Article Summary — Acids and Alkalis in Australian Workplaces | |
|---|---|
| Key Fact 1 | Hydrofluoric acid (HF) is uniquely dangerous — skin contact with concentrated HF can cause fatal systemic fluoride toxicity with minimal pain warning |
| Key Fact 2 | Alkali burns (NaOH, KOH) are often more severe than acid burns — they cause liquefactive necrosis that continues to penetrate deeper tissue |
| Key Fact 3 | Never mix acid and hypochlorite bleach — the reaction generates chlorine gas, a severe respiratory irritant and chemical warfare agent |
| Read Time | 9 min |
Common Corrosive Chemicals in Australian Industry
Corrosive chemicals (those capable of destroying living tissue on contact) are among the most commonly used hazardous substances in Australian industry, and managing them sits at the core of chemical hazards and workplace exposure standards compliance in Australia. Key industries include: electroplating (chromic acid, sulfuric acid), cleaning and sanitation (hypochlorite, phosphoric acid, caustic soda), food processing (citric acid, caustic cleaning agents), laboratory work (wide range of acids and bases), and construction (cement, lime, muriatic acid for masonry cleaning).
Key Acids: Health Effects and WES Values
Hydrochloric Acid (HCl)
WES-TWA: 1 ppm; WES-STEL: 5 ppm. HCl is a strong acid and potent upper respiratory tract irritant. Concentrated vapour causes immediate eye and throat burning — a good warning property. Mist from concentrated HCl solutions causes severe corrosive burns to skin, eyes, and airways.
Sulfuric Acid (Hâ‚‚SOâ‚„)
WES-TWA: 0.2 mg/m³ (thoracic fraction). Sulfuric acid mist is designated a Group 1 IARC carcinogen when exposure is chronic and from strong inorganic acid mists (particularly in isopropanol manufacturing using the strong acid process) — see our guide on workplace carcinogens and Australian regulatory obligations for broader context on IARC-classified substances. Causes severe burns; concentrated H₂SO₄ generates intense heat on contact with water — dilution must always be done by adding acid to water, never water to acid.
Nitric Acid (HNO₃)
WES-TWA: 2 ppm; WES-STEL: 4 ppm. Nitric acid causes distinctive yellow-orange skin staining (xanthoproteic reaction) on contact. Fuming nitric acid generates nitrogen dioxide (NOâ‚‚), a severe deep respiratory toxin with delayed-onset pulmonary oedema risk.
Hydrofluoric Acid (HF)
WES-TWA: 0.5 ppm (as F); WES-STEL: 2 ppm. HF is uniquely hazardous. Unlike other acids, dilute HF (below ~20%) causes minimal pain on skin contact initially — the burn sensation may be delayed hours. Meanwhile, fluoride ions penetrate tissue and cause progressive destruction and systemic fluoride toxicity: hypocalcaemia, hyperkalaemia, and cardiac arrhythmias. Exposure of more than 1% body surface area to concentrated HF can be fatal. Calcium gluconate gel is the emergency antidote and must be available wherever HF is used — not a substitute for immediate medical care, but a critical first-response measure.
Key Alkalis: Health Effects
Sodium Hydroxide (NaOH) / Caustic Soda
WES-TWA: 2 mg/m³ (ceiling). Concentrated NaOH solutions cause liquefactive necrosis — they saponify tissue fats and continue penetrating deeper layers unlike coagulative acid burns, which self-limit. Caustic burns to the eye are particularly devastating and can cause permanent corneal damage within minutes.
Potassium Hydroxide (KOH)
Similar hazard profile to NaOH. Used in alkaline battery production, chemical synthesis, and some cleaning operations.
Ammonia (NH₃)
WES-TWA: 25 ppm; WES-STEL: 35 ppm. Anhydrous ammonia and concentrated ammonia solution are strong alkalis that cause severe respiratory tract injury and chemical burns. Ammonia gas leaks in refrigeration plant operations have caused fatal mass casualties.
Dangerous Reactions Between Corrosives
Several combinations of commonly stored chemicals can generate toxic gases if accidentally mixed:
- Acid + hypochlorite bleach: Generates chlorine gas (Cl₂) — a potent respiratory irritant. This is the most common cause of chemical gas releases in Australian workplaces, often involving cleaning products
- Ammonia + chlorine/hypochlorite: Generates chloramines — toxic gases causing respiratory and eye irritation
- Concentrated nitric acid + organic material: Fire and explosion risk
- Concentrated sulfuric acid + water (water added to acid): Violent exothermic reaction, explosive splattering
Chemical storage must segregate acids from alkalis, and from oxidisers, to prevent accidental mixing. Written incompatibility procedures and emergency spill response plans are essential. A structured chemical risk assessment methodology provides the systematic framework for identifying these incompatibilities and implementing appropriate control measures.
First Aid for Corrosive Chemical Exposure
The universal first aid response for skin or eye contact with corrosives is immediate, copious flushing with water for a minimum of 15–20 minutes. Delay in flushing — even by seconds in the case of strong alkalis to eyes — significantly worsens outcomes. Eye wash stations compliant with AS 4775 must be within 10 seconds travel distance of any area where corrosive eye splashing is possible.
For HF skin exposure: flush with water, then apply calcium gluconate gel immediately. Call emergency services for any significant HF exposure — do not wait for symptoms. Repeated or chronic skin exposure to corrosives can also lead to occupational contact dermatitis, which requires a separate hazard management program beyond acute injury protocols.
Frequently Asked Questions
Can I keep acids and alkalis in the same storage cabinet?
No. Acids and alkalis must be stored separately. Accidental mixing of a concentrated acid with a concentrated base causes violent exothermic reactions and can generate corrosive aerosols or toxic gases. Dedicated corrosives storage cabinets with secondary containment should segregate acid and alkali families.