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Paint remover is applied to an aircraft's landing gear during an inspection looking for cracks in the aluminum

Paint stripper or paint remover is a chemical product designed to remove paint, finishes, and coatings, while also cleaning the underlying surface. Chemical paint removers are advantageous because they act on any kind of geometry and they are cheap. They can however be slow acting.^[1]

Paint can also be removed using mechanical methods (scraping or sanding) or heat (hot air, radiant heat, or steam).

Types

The selection of chemical paint removers is based on the chemical bonds that form the paint's binder. Two basic categories of chemical paint removers are caustic and solvent.

Caustics

Caustic paint removers, typically aqueous sodium hydroxide (also known as lye or caustic soda), work by breaking down the chemical bonds of the paint, usually by hydrolysis of the esters that comprise the paint film.^[1] Caustic removers must be neutralized or the new finish will fail prematurely. In addition, as caustic paint strippers typically include corrosive active ingredients, several side effects and health risks must be taken into account in using. Caustic aqueous solutions are typically used by antique dealers who aim to restore old furniture by stripping off worn varnishes, for example.

Solvents

Solvent-base paint strippers can be complex mixtures of various organic solvents, emulsifiers, thickening agents, alkaline or acid active ingredients as well as evaporation and corrosion inhibitors. Dichloromethane, also called methylene chloride, was once a popular solvent, but its use has been declining because of health concerns.^[1] Traditional solvent paint strippers penetrate the layers of paint and break the bond between the paint and the object by swelling the paint.^[2]

Aside from dichloromethane, some popular stripping solvents are N-methylpyrrolidone, dimethylformamide, benzyl alcohol, and dimethyl adipate. None of these are chlorocarbons.^[3]

Paint strippers come in a liquid, or a gel ("thixotropic") form that clings even to vertical surfaces.

Solvent strippers may also have formulations with limonene (obtained from orange peels) (or other terpene solvents). Nitromethane is another commonly used solvent. Dimethyl sulfoxide is a less toxic alternative solvent used in some formulations. Unfortunately, these alternative stripping formulas are less effective compared to those based on dichloromethane.

Alternatives

Heat guns are an alternative to chemical paint strippers. When heated, softened paint clumps and is easier to contain. High-temperature heat guns at 1,100 °F (590 °C) or more create toxic lead fumes in lead-based paint,^[4]^[5] but low-temperature heat guns and 400 °F (200 °C) infrared paint removers do not create lead fumes.^[6] Fire is a possible hazard of using heat guns.

Steam can be used on large surfaces or items to be stripped, such as window sash, can be placed inside a steam box.^[7]

Safety

A product's material safety data sheet can provides more safety information than its product labels.

Many traditional paint strippers were or are based on dichloromethane, which can pose serious health risks.^[8] It is likely a carcinogen,^[9] and is banned in some countries for consumer use.^[10] Despite this, deaths from dichloromethane are extremely rare at fewer than 2.4 cases per year^[11] and associated mostly with users applying large amounts in confined, poorly ventilated spaces. When applied in reasonable amounts and with typical levels of ventilation, or outdoors, it is generally safe to use.

Removing old lead-based paint can disperse lead and cause lead poisoning, leading several US workplace and environmental regulations address removal of old paint that could contain lead.^[12]

References

^ ^a ^b ^c Molz, Thomas (2010). "Paints and Coatings, 5. Paint Removal". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.o18_o04. ISBN 978-3-527-30385-4.
^ Active Interest Media, Inc. (May–June 2001). "Old-House Journal". Old House Journal. Active Interest Media, Inc. ISSN 0094-0178.
^ Durrani, Timur; Clapp, Robert; Harrison, Robert; Shusterman, Dennis (2020). "Solvent-based paint and varnish removers: A focused toxicologic review of existing and alternative constituents". Journal of Applied Toxicology. 40 (10): 1325–1341. doi:10.1002/jat.3979. PMID 32342556.
^ Reducing Lead Hazards when Remodeling Your Home. U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics. 1997.
^ Petit, Georges, and Donald Grant. The manufacture and comparative merits of white lead and zinc white paints. London: Scott, Greenwood & Son;, 1907. 13. Print. This source states that lead vapors are given off around 400 °F (200 °C) http://www.mediafire.com/view/1xyimc3wdo3/manufacturecompa00petirich.pdf
^ Thomas, Baker, "All About Exterior Paint", "This Old House Magazine" 2012. http://www.thisoldhouse.com/toh/photos/0,,20586187_21145196,00.html
^ Old-House Journal. Active Interest Media, Inc.
^ MacIsaac, J., Harrison, R., Krishnaswami, J., McNary, J., Suchard, J., Boysen-Osborn, M., Cierpich, H., Styles, L. and Shusterman, D. (2013), "Fatalities due to dichloromethane in paint strippers: A continuing problem". Am. J. Ind. Med. doi: 10.1002/ajim.22167 http://onlinelibrary.wiley.com/doi/10.1002/ajim.22167/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false accessed 6/1/2013
^ Nat. Toxicology Program (NTP) (NIH) (8 October 2011). Report on Carcinogens (12th Ed. ). DIANE Publishing. ISBN 978-1-4379-8736-2.
^ "Final Rule on Regulation of Methylene Chloride in Paint and Coating Removal for Consumer Use". United States Environmental Protection Agency. 22 August 2019.
^ Hoang, Anh; Fagan, Kathleen; Cannon, Dawn L.; Rayasam, Swati D. G.; Harrison, Robert; Shusterman, Dennis; Singla, Veena (2021-06-01). "Assessment of Methylene Chloride–Related Fatalities in the United States, 1980-2018". JAMA Internal Medicine. 181 (6): 797–805. doi:10.1001/jamainternmed.2021.1063. ISSN 2168-6106. PMC 8056315. PMID 33871539.
^ Beckley, Bob; Groenier, James (December 2007). "Lead-Based Paint: Planning Your Paint Removal Project". T&D Pubs. United States Forest Service. Archived from the original on 2019-02-02.