Degreasing solvents for surface treatment of metals

Solvents are commonly used to remove grease and oil. They can be applied using rags, vapour or immersion degreasing baths. Vapour degreasing uses chlorinated solvents, including:

• methylene chloride
• Epn-propyl bromide (stabilised)
• perchloroethylene.

Trichloroethylene (Trike) is now banned for most uses  - alternatives are available. Trike is classified as a category 2 carcinogen.

What you must do

Organic solvent degreasing activities can have a significant impact on air quality. You may have to take steps to prevent air pollution.

Preventing air pollution

Check whether you are affected by controls on solvent emissions.

Solvent emissions

In most circumstances, you must not use ozone depleting substances for any degreasing or solvent application, including:

• hydrochlorofluorocarbons (HCFCs)
• chlorofluorocarbons (CFCs)
• 1 t,1,1trichloroethane
• bromochloromethane (CBM)
• carbon tetrachloride.

Some vapour degreasing baths use banks of refrigerant-filled coils in the condensing zone. If you use F-gases or have old equipment containing ozone depleting substances, you must make sure that staff and contractors who service and repair refrigeration equipment comply with the controls on these substances.

Ozone-depleting substances and fluorinated gases

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

Duty of care - your waste responsibilities

You may need to deal with the following materials and substances as hazardous/special waste:

• degreasing solvent
• sump contamination (still bottoms)
• soiled, solvent-impregnated rags
• water collected in water and solvent separators.

Hazardous / special waste

Ensure that you do not make any discharge to public sewers, surface waters or groundwater without consulting the appropriate regulator. To make a discharge without the appropriate permission may be an offence and could lead to enforcement action.

Trade effluent - discharges to sewers

Preventing water pollution

Good practice

Health and Safety Executive Solvent vapour degreasing plant

• You do not need to use organic solvent degreasing techniques if this is followed by an aqueous process.
• Locate your vapour degreasing machines away from draughts (doors, windows, heating, busy passages, etc) to avoid excessive solvent loss.
• Use slow, controlled withdrawal rates when removing components from your degreasing baths. This will reduce solvent loss.
• To reduce solvent loss, put lids on your solvent containers when you are not using them. Fit lids below the exhaust extraction slots.
• Consider fitting lids to any open-top degreasing baths. Fit lids in the free-board zone.
• When replacing your equipment, choose a closed-top system as it reduces solvent consumption and energy used to heat the solvent.
• Carefully control your lip extraction rates to ensure adequate protection for staff and to prevent excessive loss of solvent.
• Jig the work so that the solvent drains freely from the piece that has been cleaned.
• Use 'squeeze' type bottles for transferring solvent onto rags.
• Do not mix different waste solvents as this could be dangerous and prevent solvents from being reclaimed.
• Consider laundering and reusing rags you use for surface cleaning.
• Carefully monitor the boiling temperature of your vapour degreasing bath. Heavily contaminated solvents have increased boiling points. This indicates that you need to change your solvent.
• Ensure that all seals work properly when you replace the sump on vapour degreasing equipment.
• Reduce the risk of spillage and land contamination by filling your degreasing systems from fixed pipework lines.