In general, solvent cleaners used in aircraft cleaning should have a flashpoint of not less than 105 °F, if explosion proofing of equipment and other special precautions are to be avoided. Chlorinated solvents of all types meet the nonflammable requirements but are toxic, and safety precautions must be observed in their use. Use of carbon tetrachloride should be avoided. The Material Safety Data Sheet (MSDS) for each solvent should be consulted for handling and safety information.
AMT’s should review the Material Safety Data Sheet (MSDS) available for any chemical, solvent or other materials they may come in contact with during the course of their maintenance activities. In particular, solvents and cleaning liquids, even those considered “environmentally friendly” can have varied detrimental effects on the skin, internal organs and/or nervous system. Active solvents such as methyl ethyl ketone (MEK) and acetone can be harmful or fatal if swallowed, and can be harmful when inhaled or absorbed through the skin in sufficient quantities.
Particular attention should be paid to recommended protective measures including gloves, respirators and face shields. A regular review of the MSDS will keep the AMT updated on any revisions that may be made by chemical manufacturers or government authorities.
Dry Cleaning Solvent
Stoddard solvent is the most common petroleum base solvent used in aircraft cleaning. Its flashpoint is slightly above 105 °F and can be used to remove grease, oils, or light soils. Dry cleaning solvent is preferable to kerosene for all cleaning purposes, but like kerosene, it leaves a slight residue upon evaporation, which may interfere with the application of some final paint films.
Aliphatic and Aromatic Naphtha
Aliphatic naphtha is recommended for wipe down of cleaned surfaces just before painting. This material can also be used for cleaning acrylics and rubber. It flashes at approximately 80 °F and must be used with care.
Aromatic naphtha should not be confused with the aliphatic material. It is toxic and attacks acrylics and rubber products, and must be used with adequate controls.
Safety solvent, trichloroethane (methyl chloroform), is used for general cleaning and grease removal. It is nonflammable under ordinary circumstances, and is used as a replacement for carbon tetrachloride. The use and safety precautions necessary when using chlorinated solvents must be observed. Prolonged use can cause dermatitis on some persons.
Methyl Ethyl Ketone (MEK)
MEK is also available as a solvent cleaner for metal surfaces and paint stripper for small areas. This is a very active solvent and metal cleaner, with a flashpoint of about 24 °F. It is toxic when inhaled, and safety precautions must be observed during its use. In most instances, it has been replaced with safer to handle and more environmentally friendly cleaning solvents.
Kerosene is mixed with solvent emulsion type cleaners for softening heavy preservative coatings. It is also used for general solvent cleaning, but its use should be followed by a coating or rinse with some other type of protective agent. Kerosene does not evaporate as rapidly as dry cleaning solvent and generally leaves an appreciable film on cleaned surfaces, which may actually be corrosive. Kerosene films may be removed with safety solvent, water emulsion cleaners, or detergent mixtures.
Cleaning Compound for Oxygen Systems
Cleaning compounds for use in the oxygen system are anhydrous (waterless) ethyl alcohol or isopropyl (anti-icing fluid) alcohol. These may be used to clean accessible components of the oxygen system such as crew masks and lines. Fluids should not be put into tanks or regulators. Do not use any cleaning compounds which may leave an oily film when cleaning oxygen equipment. Instructions of the manufacturer of the oxygen equipment and cleaning compounds must be followed at all times.