The one-stop guide to working with corrosive material: from hazard classification to tips for handling hydrofluoric acid

What are corrosive substances?

Corrosive materials cause irreversible damage to body surfaces or metals after exposure by means of a chemical reaction. Examples include many strong acids and bases (pH ≤ 2 or ≥ 11.5) and select solvents that are aggressive against tissue such as trifluoroacetic acid, hydrofluoric acid or formic acid.

Many corrosive substances have multiple hazards associated with it. Potassium permanganate for instance is an oxidizer, an irritant, and a health hazard in addition to being corrosive, while potassium hydroxide causes the corrosion of metals (e.g. aluminum, zinc) in addition to skin burn and eye damage. Corrosive substances can also be flammable such diisopropyl amine and ethylamine.

Exposure can be caused by splashes when pouring, hydrofluoric acid, spills, skin contact with contaminated containers or surfaces, splatters or mists from reactions, or inhalation of vapors from open or leaky containers, etc.

The ‘corrosion’ pictogram represents one physical and two health GHS hazard classes

Internal and/or external injuries

Corrosive dusts, corrosives that produce vapors, and corrosive gases are all capable of producing both internal (via inhalation) and/or external injuries. Corrosives that damage lung tissue may induce pulmonary edema.¹ 

Concentration and duration

The severity of chemical burns depend on the concentration, temperature, and exposure time. Momentary exposure to strong acids and bases for instance can produce severe skin damage, while weak acids and bases generally require higher concentrations or longer exposure times to produce severe burns.

Onset of pain

Exposure to corrosive acids will yield pain right away. However, it may take several hours for symptoms (e.g. redness or pain) to develop upon exposure to dilute concentrations of hydrofluoric acid (HF) or trifluoroacetic acid.¹

Damage from bases may not be felt immediately, potentially leading to a longer exposure time and deeper penetration if the person is unaware of the exposure.² Even though base exposure may not burn right away, wash with water immediately. It may also be harder to remove from the skin as bases are slippery like soap.²²

Tips for handling HF

Like other acids, the initial extent of a burn depends on the concentration, temperature, and duration of contact, but unlike other acids, fluoride ions can readily penetrate the skin, causing destruction of deep tissue layers, including bone that may continue for days.³  Exposed skin should be flushed with copious amounts of water for a minimum of 15 minutes, and calcium gluconate (2.5% gel) or iced benzalkonium chloride (0.13 % soaks) can be applied to the site of contact.⁴ Calcium gluconate or other medicine should not be applied to the eyes, and a medical examination should always be conducted following exposure. 

HF should never be stored in glass containers and minor spills (< 100 mL of solutions that are 10% or less) can be neutralized with soda ash or absorbed with vermiculite or a 3 M chemical sorbent (made of polypropylene).⁴ Evacuate the room for major spills and summon emergency personnel immediately.

Dilutions

Always add the corrosive substance to water (not the other way around) to minimize the danger of exothermic splashes. Wash corrosive substances on your skin immediately with lots of water.

Incompatible compounds

When acids attack metals, flammable hydrogen gas is often evolved, which can burn or explode if an ignition source is present. Refer to ‘Section 10: Stability and Reactivity’ of the SDS, which provides information on the chemicals that corrosives are incompatible with.

How to mitigate the risks of working with corrosives?

1. hydrofluoric acid Receiving:

• Keep a record of the chemicals in your lab. This will allow you to easily locate the materials you need, keep track of inventory to prevent an excess amount, and dispose of expired ones.
• Check new containers for defects. Confirm that the seal is intact and that there are no bulges, cracks or leaks.

2.Storage:

• Store corrosives away from incompatible materials such as combustibles.
• Smaller containers should be stored on corrosion-resistant trays, while larger containers should be surrounded by dikes in a room with sills and ramps near the door.
• Store chemicals at a height that is convenient for handling, ideally on the floor and under eye-level.
• Keep corrosives away from processing or handling areas. This reduces the chance of physical damage that may result in the event of leaks, spills, or fires.

• Storage areas should be equipped with proper ventilation and emergency equipment.
• Store corrosives in a cool, dry location that is away from direct sunlight, heat sources, and is above the freezing temperature of the chemical. When liquids freeze, they may expand and crack the container.
• Hang appropriate warning signs in and around the storage area.

 3.Handling:

• Handle corrosive material only if you are trained to do so, and inspect the storage area regularly.
• When not in use, properly seal corrosive containers.
• Wear appropriate PPE including gloves, aprons, boots, goggles, and lab coats. If necessary, use a face shield or respirator.
• Use a fume hood when working with corrosive gases, liquids that produce corrosive vapors, corrosive dusts, reactions that generate vapors or mists, or when refluxing. Always allow reflux equipment to cool before handling.
• If the dilution of a corrosive chemical is required, do so by slowly adding the corrosive substance into cold water, and stirring gently to prevent bubbling.

 4.Emergencies and spills:

• Become acquainted with emergency protocols in case of exposure.
• Equip working areas with emergency equipment including spill cleanup materials, firefighting equipment, and neutralization kits. In case of a spill or other emergency, immediately leave the area if you are unable to contain the spill/emergency. Inform your colleagues of the spill, and contact your lab manager and the fire department.
• If a corrosive substance is spilled on someone, wash the contaminated area with water for at least 15 minutes using an eyewash station or shower. Contact emergency services as soon as possible and administer first aid if necessary.

5. Alternatives:

• Review your SOP and consider substituting your reagent for a less corrosive one.
• Use the minimal amount of your corrosive reagent possible. Consider a dilution if appropriate.

6.Waste:

• Store and segregate corrosive waste in a corrosion-resistant container.
• Do not store corrosive waste in containers that once stored other chemicals or return unused corrosives to their original container as incompatible residues may be present.  Do not pour corrosive substances down the drain.

Reference:

1. Safe Operating Procedure (unl.edu)
2. 79corrosives.pdf (berkeley.edu)
3. UNIVERSITY OF NEBRASKA LINCOLN (UNL)