In this guide to Corrosives, we’ll walk you through the basic characteristics, examples and safety precautions for corrosive substances. Let’s start with explaining the definition of corrosive substances..
What are Corrosive Substances?
Corrosive substances are hazardous chemicals that cause visible destruction or permanent changes in human skin tissue at the site of contact, or are highly corrosive to steel.
Corrosive substances can be liquids, solids, or gases and can affect the eyes, skin, and respiratory tract.
The major classes of corrosives include strong acids, bases, and dehydrating agents.
Characteristics of Corrosives
Liquid corrosive chemicals are those with a pH of 4.0 or lower or a pH of 9 or higher. Solid chemicals are considered corrosive when, in solution, they fall in the above pH range.
A highly corrosive chemical has a pH of 2 or lower or a pH of 12.5 or higher.
Technically, corrosives are injurious chemicals that cause ‘full-thickness’ tissue destruction at the site of contact over a defined period of time.
No, not a nice thought at all.
Of course, this time period varies depending on the strength/pH of the substance.
Alkali injuries to the eyes are more common than injury from an acid and can be more clinically challenging, with a significant potential for long-term morbidity.
Examples of Corrosives
Some examples of corrosive materials include the following:
Strong Acids: hydrochloric, sulfuric, phosphoric
Strong Bases: hydroxides of sodium, potassium, ammonia
Strong Dehydrating Corrosives: sulfuric, phosphophrous pentoxide, calcium oxide
Strong Oxidizing Corrosives: concentrated hydrogen peroxide, sodium hypochlorite
Corrosive Solids: phosphorous, phenol
Corrosive Gases: chlorine, ammonia
As you can see, corrosive substances can come in many guises. Corrosive gases for example, can burn and destroy body tissue (especially the eyes and respiratory tract) on contact. We recently covered a fatal incident and subsequent prosecution involving ammonia gas in our Health and Safety Prosecution Latest blog.
Safety Precautions for Corrosive Substances
Let’s look at some standard safety precautions for corrosive substances that may be integrated into your workplace operating procedures.
Each substance and activity should ideally be looked at in isolation via a COSHH assessment or similar.
Purchasing Corrosive Substances
Considerations for procurement of chemicals to help reduce risk;
- Do not use corrosive chemicals if less-hazardous alternatives are possible.
- Purchase, dispense, and use the smallest quantity of corrosive chemicals possible.
- Purchase the lowest concentration of corrosive chemicals that will meet your research needs.
Make sure they are clearly and accurately labelled – ok, so this maybe seems obvious but its very easy for materials to be decanting or transferred to different container – what issue does this present – well firstly, it presents a risk to people of course, as they could confuse a hazardous material for something harmless and put themselves at risk.
Also, when it comes to environmental aspect, you need to be able to properly identify the material for safe and compliant disposal with your waste service provider.
You have to aim for simplicity here – there are COSHH labels out there e.g. Safeti labels (see below), that can be purchased which will allow you to fill in the information similar to how its presented on the original product packaging, which is what you should be aiming for.
Chemical Fume Hoods
Fume hoods can provide both physical and atmospheric protection. Work with corrosive chemicals, where feasible, should be carried out in a designated area inside of a properly functioning chemical fume hood.
Activities with some concentrated and highly toxic corrosive chemicals must always be performed in a chemical fume hood.
The fume hood is designed to capture chemical vapor and the hood sash acts as a shield in case of chemical splash. The sash must be kept closed as much as feasible.
Mechanical vacuum pumps should be used and protected from corrosive vapours using cold traps and, where appropriate, must include a filter to prevent particulate release.
Any exhaust must be vented into an approved exhaust duct or chemical fume hood.
Considerations for handling
- Do not handle corrosive chemicals when working alone.
- Immediately close all containers of corrosive chemicals after use.
- Due to the risk of splashes and equipment failures, limit the use of syringe/needles to perform transfers of corrosive chemicals in volumes of no greater than 5 mL.
- Perform liquid transfers slowly using a funnel to minimize slash, splatter, and spills.
- Do not pour water into acid. Slowly add acid to water while carefully stirring. Some corrosive chemicals will generate heat and/or release gas on contact with water.
- Reactions involving corrosive chemicals are often very exothermic. Use heat-resistant labware and allow extra volume in your vessel to account for expansion and/or foaming. It may be necessary to pre-cool solutions and cool while mixing or reacting.
Personal Protective Equipment (PPE)
Consider the potential routes of exposure and health consequences when selecting personal protective equipment (PPE) for tasks involving corrosive chemicals.
In addition to the minimum PPE requirements, other protective equipment may be necessary to reduce risks. When additional equipment (e.g. splash goggles, face shields, chemical-resistant gloves/boots/aprons) are required, an additional COSHH risk assessment and/or a safe system of work may also be necessary.
An example of a task that would require additional eye/face protection:
- Transfers of corrosive liquids outside of the fume hood.
- Due to the increased risk of splash to the face and eyes when there is no hood sash to shield the worker, tight-fitting chemical-splash goggles and a face shield are required
Examples of a tasks that require specialty gloves:
- When prolonged contact or immersion of hands in corrosive liquid is anticipated
- When large volumes of corrosive liquids are being transferred
- Handling particularly toxic corrosive chemicals
Here’s a quick 60 second tip from one of our YouTube short videos >>>>>>>>>>>>>>>>>>>
Decontamination and Waste
A couple of simple tips on keeping personnel safe when using corrosive chemicals.
- Wash hands thoroughly with soap and water after handling any chemical and whenever you leave the lab.
- Use good housekeeping practices to avoid contamination of surfaces, garments, personal belongings, and self.
3. Decontaminate all surfaces that have come in contact with corrosive chemicals and clean-up small spills promptly.
Corrosive chemicals are definitely considered hazardous wastes. Make sure to closely liaise with an authorised hazardous waste company to safely and securely dispose of your hazardous waste streams.