Bluing baths used by machinery or electrical equipment businesses

This guidance is relevant if you manufacture small arms.

What is bluing?

Bluing is a technique that prevents the steel parts of a gun from corroding.

Chemical hot caustic bluing is the main method used in UK small arms manufacture. It involves cleaning the steel and placing it into:

1.  a treatment tank with a solution of ammonium nitrate, sodium hydroxide, sodium nitrite and water heated at around 300°C
2.  a boiling water bath to remove bluing salts
3.  an oil finishing bath.

What you must do

Comply with your permit, licence or exemption

If you produce explosives you must have an environmental permit or pollution prevention and control (PPC) permit.

Explosives

If you have a permit, licence or exemption you must comply with its conditions, including any conditions about using chemicals or carrying out your treatment processes. If you do not comply with conditions you can be fined or even sent to prison.

Prevent nuisance

If you mix ammonium nitrate solutions you will produce ammonia gas, which has a very strong odour.

If your activities create odours that disturb your neighbours, your local council can issue you with an abatement notice that:

  • requires you to reduce the nuisance
  • stops or places restrictions on your operations
  • requires you to carry out work or take other steps to reduce or stop the nuisance from reoccurring.

Anyone affected by the nuisance, such as your neighbours, can apply to the court in England, Northern Ireland or Wales or the sheriff in Scotland to issue you with an abatement notice.

You can be fined if you do not comply with an abatement notice, and your local authority can take steps to stop the nuisance and charge you for its costs.

For further information on nuisance, see our guidance on noise, odour and other nuisances.

Check if you need any permits, consents or other authorisations to discharge water

Do not discharge to public sewers, surface waters or groundwater without consulting your regulator. You may need an environmental permit or trade effluent agreement (England and Wales) or discharge consent, groundwater authorisation or other authorisation (Northern Ireland and Scotland). For further information, see our guidance on discharges to water and sewer.

Comply with your waste responsibilities

You must comply with your duty of care responsibilities when dealing with waste.

You may need to deal with substances from your bluing baths as hazardous/special waste because they have corrosive and irritant properties or are contaminated with heavy metals.

For further information, see our guidance on hazardous/special waste.

Good practice

Prevent spills at your site

Install splash guards, drip trays and bunds around bluing baths and treatment areas to contain any leaks or spills at your site.

Mop up any spills rather than rinsing them down to reduce the volume of wastewater you produce.

Mix solutions of ammonium nitrate and sodium hydroxide very slowly to avoid the mixture boiling over the top of the treatment vessel.

Reduce your emissions

Use extraction equipment to remove fumes from your work area and service your extraction system regularly.

Use de-ionised water instead of tap water to make up your bluing solution as this will produce less sludge.

De-water tank bottom sludges to reduce the volume of waste that you produce.

Cover your treatment baths when they are not in use to reduce evaporation.

Use polypropylene balls or chroffles to cover your heated tanks as this will reduce your energy consumption and emissions.

You must not make any discharge to surface water or groundwater without consulting your environmental regulator. If you discharge without an authorisation, permit or consent from your environmental regulator you could be prosecuted and fined or imprisoned.

Water pollution

You must not discharge trade effluent to a public sewer without trade effluent consent or a trade effluent agreement with your water and sewerage company or authority. If you discharge without a consent or agreement you could be prosecuted and fined or imprisoned.

Trade effluent - discharges to sewers

If you store oil you may need to comply with the requirements of the Oil Storage Regulations.

You must comply with your Duty of Care responsibilities when dealing with waste.

If the material that you are handling has hazardous properties, you may need to deal with it as hazardous/special waste. Chemical blueing tanks produce potentially hazardous liquid wastes that may have corrosive and irritant properties or be contaminated with heavy metals.

If you supply a potentially hazardous chemical, you may have to provide a safety data sheet (SDS). The SDS tells the user how to handle, store and dispose of hazardous chemicals.

For guidance about when to provide an SDS and what it should include, see the Health and Safety Executive (HSE) leaflet.

HSE: REACH and safety data sheets (Adobe PDF - 111KB)

If you don’t receive an SDS with a chemical, you can contact the supplier and ask for one. Suppliers who do not provide adequate instructions for using their products safely may be breaking the law.

Good practice

  • Mixing ammonium nitrate and sodium hydroxide releases heat. Mix the solution very slowly to avoid the mixture boiling over the top of the treatment vessel.
  • Ensure that your extraction system is regularly serviced.
  • Chemical fume suppressants that reduce or control misting by reducing the surface tension of the bath are available for certain applications. You should only normally use such suppressants in conjunction with another emission control technique, such as lip extraction.
  • Cover treatment baths when they are not in use to reduce evaporative losses.
  • Clearly label all rinse and treatment baths to ensure your employees can easily identify each.
  • Contain leaks and spills by installing splash guards and drip trays around baths.
  • If there is a spill, mop it up rather than rinsing it down. This will reduce the volume of wastewater produced.
  • The average drain time for manual lines is around three seconds. Drain times of 10 seconds or more can reduce drag-out by more than 40%. Establish and record procedures that specify drain time and rinse methods. Train and regularly audit your staff to ensure that they consistently use the appropriate procedure.
  • Agitate rinse baths (manually or by air agitation) to promote better rinsing.
  • Use polypropylene balls (chroffles) on heated tanks to reduce energy consumption and emissions.
  • Cover your tanks when they are not in use to reduce emissions to air.
  • Have your waste oil laundered or refined and returned to you.
  • To reduce sludge generation, use de-ionised water instead of tap water to make up your blueing solution.
  • De-water tank bottom sludges to cut the volume of waste that you produce and your waste management charges.
  • Bund all your treatment tanks, or the area of the shop floor that holds the treatment tanks. This will reduce the risk of spills contaminating land or water.