View source for Rustproofing

{{Short description|Prevention of rusting of iron and steel objects}}
{{about|anti-corrosion treatment of road vehicles|more general coverage|Corrosion}}
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[[File:Rusty car bodywork rusted through in BMW 318i E46 - free stock photo with attribution CC-BY.jpg|right|thumb|Severe car body corrosion example]]
'''Rustproofing''' is the prevention or delay of [[rust]]ing of [[iron]] and [[steel]] objects, or the permanent [[wikt:protection|protection]] against [[corrosion]]. Typically, the protection is achieved by a process of [[surface finishing]] or treatment. Depending on mechanical wear or environmental conditions, the [[Chemical decomposition|degradation]] may not be stopped completely, unless the process is periodically repeated.{{citation needed lead|date=July 2020}}<!-- there is no support for this statement in the citations in the article body; also, this would seem perhaps to only be talking about some particular aspect of the vehicle getting "peridically repeated", since no process exists for periodically repeating the entire early paint manufacturing process of automobiles for cars that have been out on the streets for a while; but which part is not made clear --> The term is particularly used in the [[automobile industry]].{{citation needed|date=January 2015}}

==Vehicle rustproofing==
===Factory===
In the factory, car bodies are protected with special chemical formulations.

Typically{{according to whom|date=July 2020}}, [[phosphate conversion coating]]s were used.{{when|date=July 2020}}{{by whom|date=July 2020}} Some firms [[galvanization|galvanize]]d part or all of their car bodies before the [[Primer (paint)|primer]] coat of paint was applied.{{citation needed|date=April 2016}} If a car is [[body-on-frame]], then the frame (chassis) must also be rustproofed. In traditional automotive manufacturing of the early- and mid-20th century, paint was the final part of the rustproofing barrier between the body shell and the atmosphere, except on the underside. On the underside, an [[underseal]] rubberized or [[PVC]]-based coating was often sprayed on.{{when|date=July 2020}} These products will be breached eventually and can lead to unseen corrosion that spreads underneath the underseal. Old 1960s and 1970s rubberized underseal can become brittle on older cars and is particularly liable to this.{{citation needed|date=May 2015}}

The first [[Electrophoretic deposition|electrodeposition]] [[primer (paint)|primer]] was developed in the 1950s, but were found to be impractical for widespread use. Revised [[cathodic]] automotive electrocoat primer systems were introduced in the 1970s that markedly reduced the problem of corrosion that had been experienced by a vast number of automobiles in the first seven decades of automobile manufacturing. Termed '''e-coat'''<!-- bolded per [[WP:MOSBOLD]] as a redirect target -->, "electrocoat automotive primers are applied by totally submerging the assembled car body in a large tank that contains the waterborne e-coat, and the coating is applied through cathodic electrodeposition. This assures nearly 100% coverage of all metal surfaces by the primer. The coating chemistry is waterborne enamel based on [[epoxy]], an [[aminoalcohol]] [[adduct]], and blocked [[isocyanate]], which all [[crosslink]] on baking to form an epoxy-urethane resin system.<ref name=aca2020/>

E-coat resin technology, combined with the excellent coverage provided by electrodeposition, provides one of the more effective coatings for protecting steel from corrosion. For modern automobile manufacturing after the 1990s, nearly all cars use e-coat technology as base foundation for their corrosion protection coating system.<ref name=aca2020>{{cite web |url=https://www.paint.org/coatingstech-magazine/articles/brief-history-automotive-coatings-technology/ |title=A Brief History of Automotive Coatings Technology |year=2020 |publisher=American Coatings Association |accessdate=8 July 2020 }}</ref>

===Aftermarket===
Aftermarket kits are available to apply rustproofing compounds both to external surfaces and inside enclosed sections, for example sills/rocker panels (see [[monocoque]]), through either existing or specially drilled holes. The compounds are usually wax-based and can be applied by aerosol can, brush, low pressure pump up spray, or compressor fed spray gun.

An alternative for sills/rocker panels is to block drain holes and simply fill them up with wax and then drain most of it out (the excess can be stored and reused), leaving a complete coating inside. Anti-rust wax like [[phosphoric acid]] based rust killers/neutralizers can also be painted on already rusted areas. Loose or thick rust must be removed before anti-rust wax like [[Waxoyl]] or a similar product is used.{{original research inline|date=July 2020}}

Structural rust (affecting structural components which must withstand considerable forces) should be cut back to sound metal and new metal welded in, or the affected part should be completely replaced. Wax may not penetrate [[spot welding|spot-welded]] seams or thick rust effectively. A thinner (less viscous) mineral-oil-based anti-rust product followed by anti-rust wax can be more effective.{{according to whom|date=July 2020}} Application is easier in hot weather rather than cold because even when pre-heated, the products are viscous and don't flow and penetrate well on cold metal.{{citation needed|date=July 2020}}

Aftermarket "underseals" can also be applied.  They are particularly useful in high-impact areas like wheel arches. There are two types - drying and non-drying. The hardening and drying products are also known as "Shutz" and "Anti Stone Chip" with similar potential problems to the original factory underseals.{{citation needed|date=May 2015}} These are available in black, white, grey and red colors and can be overpainted. These are best used for the area below the bumpers on cars that have painted metal body work in that location, rather than modern plastic deep bumpers. The [[bitumen]] based products do not dry and harden, so they cannot become brittle, like the confusingly named "Underbody Seal with added Waxoyl" made by Hammerite, which can be supplied in a Shutz type cartridge labelled "Shutz" for use with a Shutz compressor fed gun.<ref>{{cite web|url=http://www.hammerite.co.uk/products/underbody_seal.jsp|title=Underbody Seal|publisher=}}</ref> Mercedes bodyshops use a similar product supplied by Mercedes-Benz.<ref>{{cite web|url=http://forums.mercedesclub.org.uk/archive/index.php/t-49946.html|title=hammerite underseal with waxoil (Black stuff) [Archive] - Mercedes-Benz Owners' Forums|publisher=}}</ref> There are many manufacturers of similar products at varying prices, these are regularly group tested and reviewed in the classic car magazine press.

The non drying types contain anti-rust chemicals similar to those in anti-rust waxes. Petroleum-based rust-inhibitors provide several benefits, including the ability to creep over metal, covering missed areas.{{citation needed|date=May 2015}} Additionally, a petroleum, solvent-free rust inhibitor remains on the metal surface, sealing it from rust-accelerating water and oxygen. Other benefits of petroleum-based rust protection include the self-healing properties that come naturally to oils, which helps undercoatings to resist abrasion caused by road sand and other debris. The disadvantage of using a petroleum-based coating is the film left over on surfaces, rendering these products too messy for top side exterior application, and unsafe in areas where it can be slipped on. They also cannot be painted.{{citation needed|date=July 2020}}

There are aftermarket electronic "rustproofing" technologies claimed to prevent corrosion by "pushing" electrons into the car body, to limit the combination of oxygen and iron to form rust. The loss of electrons in paint is also claimed to be the cause of “paint oxidisation” and the electronic system is also supposed to protect the paint.<ref>{{cite web |url=http://rustproof.com.au/faq/ |title=FAQ - Is the electronic system environmentally friendly? |author=Tom Green |date=17 August 2016 |publisher=Downey Street Rushproofing |access-date=17 August 2016}}</ref> However, there is no peer reviewed scientific testing and validation supporting the use of these devices and corrosion control professionals find they do not work.<ref>[http://www.nace.org/StarterApps/Wiki/Dynamic.aspx?id=367&__taxonomyid=225 NACE International Article Electronic Rust Prevention]</ref><ref>
Baboian, R., "State of the Art in Automobile Cathodic Protection," SAE Technical Paper 912270, 1991, doi:10.4271/912270</ref>

===Rate of corrosion===
The rate at which vehicles corrode is dependent upon:{{original research inline|date=July 2020}}

*Local climate and use of [[Ice melt|ice-melting chemicals]] ([[salt]]) upon the roads
*Atmospheric pollution, such as [[acid rain]] or [[salt spray]], which can cause paint damage
*Quality, thickness, and composition of metal used, often an alloy of [[mild steel]]
*Improper use of some dissimilar metals, which can accelerate the rusting of steel bodywork through [[electrolytic corrosion]]
*Design of "rust traps" (nooks and crannies that collect road dirt and water)
*Particular process of rustproofing used
*Plastic/under-seal protection on the car underside
*Exposure to salt water, which strips off the protective paint and also causes rust much more quickly than ordinary rain water would

==Rustproof alloys==
[[Stainless steel]], also known as "inox steel" does not stain, corrode, or rust as easily as ordinary steel. [[Pierre Berthier]], a Frenchman, was the first to notice the rust-resistant properties of mixing chromium with alloys in 1821, which led to new metal treating and metallurgy processes, and eventually the creation of usable stainless steel. [[DMC DeLorean|DeLorean]] cars had a fiberglass body structure with a steel backbone chassis, along with external brushed stainless-steel body panels.

Some cars have been made from aluminum, which may be more corrosion resistant than steel when exposed to water, but not to salt or certain other chemicals.{{citation needed|date=May 2015}}

[[Weathering steel]], often referred to by the [[Generic trademark|genericised trademark]] COR-TEN steel and sometimes written without the hyphen as corten steel, is a group of steel alloys which were developed to eliminate the need for painting by forming a stable external layer of [[rust]]. [[U.S. Steel|U.S. Steel (USS)]] holds the [[Trademark|registered trademark]] on the name COR-TEN.<ref>{{cite web |title=Trademarks and Ownership |url=https://www.ussteel.com/posts/trademarks-and-ownership |publisher=USS |access-date=21 October 2024}}</ref> The name COR-TEN refers to the two distinguishing properties of this type of [[steel]]: [[corrosion]] resistance and [[tensile strength]].<ref>{{cite web |title=Weathering Steel: A Guide to Corten and the A/B Equivalents, Origins & Standards |url=https://www.azom.com/article.aspx?ArticleID=12974 |website=AZoM.com |date=21 October 2024}}</ref>

==See also==
{{div col}}
* [[Corrosion]]
* [[Corrosion engineering]]
* [[Hot-dip galvanizing]]
* [[Tinning]]
* [[Iron pillar of Delhi]]
* [[Cathodic protection#Automobiles|Cathodic Protection for Vehicles]]
* [[Cosmoline]]
* [[Corrosion inhibitor]]
{{div col end}}

==References==
{{Reflist}}

{{commons category|Rust}}

[[Category:Vehicle technology]]
[[Category:Corrosion prevention]]
[[Category:Materials science]]