Brake cleaner, often also called '' parts cleaner'', is a mostly colorless cleaning agent, mainly used for cleaning the brake disks, the engine compartment and underfloor of motor vehicles. An important feature is that the brake cleaner leaves no residue after the solvents evaporate.
Explosionsschutz beim Umgang mit brennbaren Reinigern in der Kfz-Werkstatt (PDF; 762 kB).
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Composition

Chlorinated brake cleaners (often sold as non-flammable) use

organochloride An organochloride, organochlorine compound, chlorocarbon, or chlorinated hydrocarbon is an organic compound containing at least one covalently bonded atom of chlorine. The chloroalkane class (alkanes with one or more hydrogens substituted by chlo ...

s like

tetrachloroethylene Tetrachloroethylene, also known under the systematic name tetrachloroethene, or perchloroethylene, and many other names (and abbreviations such as "perc" or "PERC", and "PCE"), is a chlorocarbon with the formula Cl2C=CCl2 . It is a colorless li ...

and dichloromethane. Historically

1,1,1-Trichloroethane The organic compound 1,1,1-trichloroethane, also known as methyl chloroform, is a chloroalkane. This colorless, sweet-smelling liquid was once produced industrially in large quantities for use as a solvent. It is regulated by the Montreal Prot ...

was used, sometimes together with Tetrachloroethylene. It was phased out due to its ozone-depleting nature. Non-chlorinated brake cleaners use

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

s as a main component; it will either be a low-boiling aliphatic compound or higher-boiling hydrocarbon mixture.

Aromatics Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past groupin ...

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) a ...

xylene In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are s ...

may also be used. The hydrocarbons used are sometimes made by

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organ ...

from

naphtha Naphtha ( or ) is a flammable liquid hydrocarbon mixture. Mixtures labelled ''naphtha'' have been produced from natural gas condensates, petroleum distillates, and the distillation of coal tar and peat. In different industries and regions ' ...

. The

lipophilic Lipophilicity (from Greek λίπος "fat" and φίλος "friendly"), refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such non-polar solvents are themselves lipo ...

liquids dissolve fat-soluble lubricants or oils. Some products also contain polar solvents such as

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

, methanol, isopropanol, and

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...

in order to dissolve non-lipophilic substances. Many formulations are incompatible with various materials, especially plastics.

Use

The main application of brake cleaners is the

degreasing Degreasing, often called defatting or fat trimming, is the removal of fatty acids from an object. In culinary science, degreasing is done with the intention of reducing the fat content of a meal. Degreasing food Degreasing is often used by diete ...

and cleaning metal parts or metallic surfaces. They are used for removing oils, fats, resins, tar and dust, mainly in the automotive sector. About 10 million liters are consumed per year in Germany.

Danger

Brake cleaners contain toxic compounds and should only be used in well-ventilated areas or outdoors. Some are highly flammable and harmful for

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

, which also has to be considered during storage. Skin exposure to the solvent mixture may cause irritation and defatting injury. Chlorinated brake cleaner containing tetrachloroethylene will, on exposure to high temperatures (above ) or strong UV light, decompose into phosgene and

hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...

, both of which are extremely dangerous if inhaled.{{cite journal , last1=Wettström , first1=R. , title=Phosgene Formation During Welding in Air Contaminated with Perchloroethylene , last2=Dahlberg , first2=J. A. , last3=Andersson , first3=H. F. , url=https://academic.oup.com/annweh/article-abstract/18/2/129/289655?redirectedFrom=PDF , journal=The Annals of Occupational Hygiene , volume=18 , issue=2 , accessdate=2 July 2019 , pages=129–132 , language=en , doi=10.1093/annhyg/18.2.129 , pmid=1190647 , date=1 September 1975

Rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, an ...

and some types of

plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...

s are decomposed by brake cleaners by removing binding components. This has the consequence that the rubber will appear unchanged at first; however, it will become

brittle A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Br ...

, and after a few weeks to months cracks and fractures appear.

Alternatives

For frequent and industrial use, cleaning and degreasing may be an alternative to supercritical carbon dioxide or dry Ice blasting, which is

abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...

. This requires a setup to apply the carbon dioxide. While the harmful vapors are eliminated, the CO₂ must be ventilated. Applying the carbon dioxide causes electrostatic discharge by the expanding gas. The dust and harmful brake dust is not bound in the liquid.

References

Cleaning products Vehicle braking technologies Pages with unreviewed translations