Lost Time Injury Alert
Acids used to etch, pickle or passivate in stainless steel fabrication shops are highly corrosive and, under some circumstances, highly reactive. Where these acids are stored, mixed or used, good occupational health and safety practices need to be implemented.
In July 1996, the laboratory supervisor at a major stainless steel processing facility sustained a severe eye injury when a mixture of 25ml concentrated hydrochloric acid, 25ml concentrated nitric acid and 50ml iso-propyl alcohol burst through the top of the storage bottle and splashed into his right eye. He also sustained acid burns to his temple, the back of his head, behind his ear, and to the inside of his right forearm.
The supervisor had a Metallurgy Certificate and fifteen years' laboratory experience.
WorkCover subsequently supplied information on one of the root causes of the accident, a similar accident having occurred about a month earlier in another workplace in the same suburb. The following information is published in Bretherick's Handbook of Reactive Chemical Hazards (edited by P G Urben, 5th Edition, Volume 1, published by Butterworths Heinemann):
"Mixtures of nitric acid and alcohols ('Nital') are quite unstable when the concentration of the acid is above 10%, and mixtures containing over 5% should not be stored. The use of a little alcohol and excess nitric acid to clean sintered glassware (by 'nitric acid fizzing') is not recommended. At best, it is a completely unpredictable approximation to a nitric acid-alcohol rocket propulsion system. At worst, if heavy metals are present, fulminates capable of detonating the mixture may be formed."
When working with corrosive chemicals, good, safe working practices should be adopted, including the following:
- Personal Protective Equipment (PPE) - face mask, apron, rubber gloves - should be worn at all times;
- Acids and alcohols should only be mixed in a fume cupboard or vented area;
- The acid should be added to the diluent, not the other way around;
- Mixed acids should be stored in vessels with ground glass stoppers which allow venting - not screw top containers;
- Goggles should be worn during all work with alkalies, e.g. sodium hydroxide, as alkalies are particularly injurious to the eye; and
- No assumptions should be made if unexpected reactions occur.