Galvanization: Difference between revisions
imported>Chetvorno →Protective action: Added it's main function, cathodic protection, which had somehow been omitted from this section |
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[[File:Feuerverzinktes Geländer.jpg|thumb|right|Galvanized surface with visible spangle]] | [[File:Feuerverzinktes Geländer.jpg|thumb|right|Galvanized surface with visible spangle]] | ||
'''Galvanization''' ([[American and British English spelling differences|also spelled]] '''galvanisation''')<ref>{{cite web|title=Galvanize|work=[[Cambridge English Dictionary]]|url=https://dictionary.cambridge.org/dictionary/english/galvanize|access-date=10 November 2019}}</ref> is the process of applying a protective [[zinc]] coating to [[steel]] or [[iron]], to prevent [[rusting]]. The most common method is [[hot-dip galvanization|hot-dip galvanizing]], in which the parts are coated by submerging them in a bath of hot, molten zinc.<ref>{{Cite web |title=What is the HDG Process? |url=https://galvanizeit.org/hot-dip-galvanizing/hdg-process |access-date=2025-03-12 |website=American Galvanizers Association |language=en}}</ref> | [[File:The rustiest letter box in Bavaria.jpg|thumb|Protective effect: completely rusted letter box mounted to a hot-dip galvanized wall]] | ||
'''Galvanization''' ([[American and British English spelling differences|also spelled]] '''galvanisation''')<ref>{{cite web|title=Galvanize|work=[[Cambridge English Dictionary]]|url=https://dictionary.cambridge.org/dictionary/english/galvanize|access-date=10 November 2019}}</ref> is the process of applying a protective [[zinc]] coating to [[steel]] or [[iron]], to prevent [[rusting]]. The most common method is [[hot-dip galvanization|hot-dip galvanizing]], in which the parts are coated by submerging them in a bath of hot, molten zinc.<ref>{{Cite web |title=What is the HDG Process? |url=https://galvanizeit.org/hot-dip-galvanizing/hdg-process |access-date=2025-03-12 |website=American Galvanizers Association |language=en}}</ref> | |||
'''Galvanized steel''' is widely used in applications where [[corrosion resistance]] is needed without the cost of [[stainless steel]], and is considered superior in terms of cost and life-cycle. It can be identified by the [[crystallization]] patterning on the surface (often called a "spangle").<ref name="galvinfo">{{cite web |author=GalvInfo |date=August 2011 |title=GalvInfoNote / The Spangle on Hot-Dip Galvanized Steel Sheet |url=http://galvinfo.com/ginotes/GalvInfoNote_2_6.pdf |url-status=dead |archive-url=https://web.archive.org/web/20140302192219/http://galvinfo.com/ginotes/GalvInfoNote_2_6.pdf |archive-date=2 March 2014 |access-date=27 February 2014 |publisher=GalvInfo}}</ref> | |||
Galvanized steel can be [[Welding|welded]]; however, welding gives off toxic zinc fumes. Galvanized fumes are released when the galvanized metal reaches a certain temperature. This temperature varies by the galvanization process used. In long-term, continuous exposure, the recommended maximum temperature for hot-dip galvanized steel is {{convert|200|C|F}}, according to the American Galvanizers Association. The use of galvanized steel at temperatures above this will result in peeling of the zinc at the ''inter-metallic'' layer.<ref>{{Cite web |date=2020-03-02 |title=Performance and Inspection of HDG Exposed to Extreme Temperatures |url=https://galvanizeit.org/knowledgebase/article/performance-and-inspection-of-hdg-exposed-to-extreme-temperatures |access-date=2025-06-08 |website=American Galvanizers Association |language=en}}</ref> | |||
Like other corrosion protection systems, galvanizing protects steel by acting as a barrier between steel and the atmosphere. However, zinc is a more electropositive (active) metal in comparison to steel. This is a unique characteristic for galvanizing, which means that when a galvanized coating is damaged and steel is exposed to the atmosphere, zinc can continue to protect steel through [[galvanic corrosion]] (often within an annulus of 5 mm, above which electron transfer rate decreases). | |||
==History and etymology== | ==History and etymology== | ||
[[File:NailsCloseup.jpg|thumb|Galvanized nails]] | [[File:NailsCloseup.jpg|thumb|Galvanized nails]] | ||
The process is named after the Italian physician, physicist, biologist and philosopher | The process is named after the Italian physician, physicist, biologist and philosopher [[Luigi Galvani]] (9 September 1737 – 4 December 1798). The earliest known example of galvanized iron was discovered on an Indian armour in the [[Royal Armouries]] Museum collection in the United Kingdom, known from inscriptions to be earlier than the 1680s<ref>[https://web.archive.org/web/20150327062539/http://royalarmouries.org/what-we-do/research/analytical-projects/zinc-coatings-of-indian-plate-and-mail-armour ZINC COATINGS OF INDIAN PLATE AND MAIL ARMOUR]. Summary of XRF analysis conducted in September 1999 by the Royal Armouries Museum in Leeds and written up as part of a thesis by Helen Bowstead Stallybrass at the Department of Archaeological Sciences, [[Bradford University]].</ref> | ||
The term "galvanized" can also be used metaphorically of any stimulus which results in activity by a person or group of people.<ref>{{cite book|title=The Oxford English Dictionary|edition=2|volume=VI|publisher=Oxford University Press|page=340|editor-last=Murray | editor-first = James A. H. |display-editors=etal|isbn=0 19 861218-4|url-access=registration|url=https://archive.org/details/oxfordenglishdic6simp/page/340|year=1989}}</ref> | The term "galvanized" can also be used metaphorically of any stimulus which results in activity by a person or group of people.<ref>{{cite book|title=The Oxford English Dictionary|edition=2|volume=VI|publisher=Oxford University Press|page=340|editor-last=Murray | editor-first = James A. H. |display-editors=etal|isbn=0 19 861218-4|url-access=registration|url=https://archive.org/details/oxfordenglishdic6simp/page/340|year=1989}}</ref> | ||
In modern usage, the term "galvanizing" has largely come to be associated with zinc coatings, to the exclusion of other metals. Galvanic paint, a precursor to [[hot-dip galvanizing]], was patented by [[Stanislas Sorel]], of Paris, on June 10, 1837, as an adoption of a term from a highly fashionable field of contemporary science, despite having no evident relation to it.<ref>{{cite journal|url=https://books.google.com/books?id=W8oGAAAAYAAJ&dq=%22Specification+of+a+Patent+for+a+process+for+protecting+articles+made+of+Iron+or+Steel+from+oxidation.%22&pg=PA52 |title= Specification of a Patent for a process for protecting articles made of Iron or Steel from oxidation|author= Sorel, M. |journal= Journal of the Franklin Institute (Philadelphia, Pa.)|publisher= Pergamon Press|date= 1838}}</ref> | In modern usage, the term "galvanizing" has largely come to be associated with zinc coatings, to the exclusion of other metals. Galvanic paint, a precursor to [[hot-dip galvanizing]], was patented by [[Stanislas Sorel]], of Paris, on June 10, 1837, as an adoption of a term from a highly fashionable field of contemporary science, despite having no evident relation to it.<ref>{{cite journal|url=https://books.google.com/books?id=W8oGAAAAYAAJ&dq=%22Specification+of+a+Patent+for+a+process+for+protecting+articles+made+of+Iron+or+Steel+from+oxidation.%22&pg=PA52 |title= Specification of a Patent for a process for protecting articles made of Iron or Steel from oxidation|author= Sorel, M. |journal= Journal of the Franklin Institute (Philadelphia, Pa.)|publisher= Pergamon Press|date= 1838}}</ref> | ||
==Principle== | |||
The zinc coating, when intact, prevents corrosive substances from reaching the underlying iron.<ref>{{cite web |title=How to Galvanize Metal to Protect Pipes |url=https://www.appmfg.com/blog/how-to-galvanize-metal-to-protect-pipes |website=www.appmfg.com |access-date=3 February 2022 |language=en}}</ref> Its main function is to act as a [[sacrificial anode]] to prevent the iron from rusting by [[cathodic protection]]. Zinc is more reactive than iron, so the zinc coating preferentially oxidizes to zinc carbonate, preventing the iron from corroding, even if there are gaps in the zinc coating. Additional [[electroplating]] such as a [[chromate conversion coating]] may be applied to provide further [[Passivation (chemistry)#Surface passivation|surface passivation]] to the substrate material.<ref>{{cite journal |last1=Magalhães |first1=A.A.O |last2=Margarit |first2=I.C.P |last3=Mattos |first3=O.R |title=Electrochemical characterization of chromate coatings on galvanized steel |journal=Electrochimica Acta |date=July 1999 |volume=44 |issue=24 |pages=4281–4287 |doi=10.1016/S0013-4686(99)00143-7 }}</ref> | |||
== Corrosion == | |||
[[File:Rust 1.jpeg|thumb|right|Rusted corrugated steel roof]] | |||
Galvanized steel can last for many decades if other supplementary measures are maintained, such as [[paint]] coatings and additional [[sacrificial anode]]s. Corrosion in non-salty environments is caused mainly by levels of [[sulfur dioxide]] in the air.<ref>{{cite web|url=http://www.galvanizing.org.uk/about_galvanizing/corrosion_performance/atmospheric_resistance |title=Atmospheric Resistance |publisher=Galvanising Association (UK) |url-status=dead |archive-url=https://web.archive.org/web/20140222165139/http://www.galvanizing.org.uk/about_galvanizing/corrosion_performance/atmospheric_resistance |archive-date=2014-02-22 }}</ref> | |||
==Methods== | ==Methods== | ||
[[Hot-dip galvanizing]] deposits a thick, robust layer of zinc iron alloys on the surface of a steel item | [[Hot-dip galvanizing]] deposits a thick, robust layer of zinc iron alloys on the surface of a steel item. The hot-dip process generally does not reduce strength to a measurable degree, with the exception of high-strength steels where [[hydrogen embrittlement]] can become a problem.<ref>{{cite web |url=http://www.galvanizeit.org/designing-fabricating/design-considerations/steel-selection/ |publisher=American Galvanizers Association |title=Steel Selection |access-date=3 April 2015 |archive-date=21 August 2013 |archive-url=https://web.archive.org/web/20130821041723/http://www.galvanizeit.org/designing-fabricating/design-considerations/steel-selection |url-status=dead }}</ref> | ||
Galvanization can be done using electricity in [[electrogalvanization]]. | |||
== | [[Sherardizing]] provides a zinc diffusion coating on iron- or copper-based materials.<ref name="Zinchand">{{cite book |last1=Porter |first1=Frank C. |title=Zinc Handbook |date=1991 |doi=10.1201/9781482276947 |isbn=978-1-4822-7694-7 |chapter=Sherardizing |pages=292–301 }}</ref><ref name="MittemeijerSomers2014">{{cite book |last1=Natrup |first1=F. |last2=Graf |first2=W. |title=Thermochemical Surface Engineering of Steels |chapter=Sherardizing: Corrosion protection of steels by zinc diffusion coatings |date=2015 |pages=737–750 |doi=10.1533/9780857096524.5.737 |isbn=978-0-85709-592-3 }}</ref> | ||
== Common use == | |||
== | === Construction steel === | ||
This is the most common use for galvanized metal; hundreds of thousands of tons of steel products are galvanized annually worldwide. In developed countries, most larger cities have several galvanizing factories, and many items of steel manufacture are galvanized for protection. Typically these include street furniture, building frameworks, balconies, verandahs, staircases, ladders, walkways, and more. Hot dip galvanized steel is also used for making steel frames as a basic construction material for steel frame buildings.<ref>{{Cite web|last=marshall|date=2019-10-11|title=Galvanized Steel: Types, Uses, Benefits|url=https://punjabpipestore.com/gi-pipes/|access-date=2021-02-06|website=National Material Company – Steel Processing Facilities|language=en-US}}</ref> | This is the most common use for galvanized metal; hundreds of thousands of tons of steel products are galvanized annually worldwide. In developed countries, most larger cities have several galvanizing factories, and many items of steel manufacture are galvanized for protection. Typically these include street furniture, building frameworks, balconies, verandahs, staircases, ladders, walkways, and more. Hot dip galvanized steel is also used for making steel frames as a basic construction material for steel frame buildings.<ref>{{Cite web|last=marshall|date=2019-10-11|title=Galvanized Steel: Types, Uses, Benefits|url=https://punjabpipestore.com/gi-pipes/|access-date=2021-02-06|website=National Material Company – Steel Processing Facilities|language=en-US}}</ref> | ||
== | === Piping === | ||
{{See also|Galvanic corrosion|Pipe (fluid conveyance)|Piping}} | {{See also|Galvanic corrosion|Pipe (fluid conveyance)|Piping}} | ||
In the early 20th century, galvanized piping swiftly took the place of previously used [[Cast iron pipe|cast iron]] and [[Pipe (fluid conveyance)#Materials|lead]] in [[Tap water|cold-water]] [[plumbing]]. Galvanized piping rusts from the inside out, building up layers of plaque on the inside of the piping, causing both water pressure problems and eventual pipe failure. These plaques can flake off, leading to visible impurities in water and a slight metallic taste. The life expectancy of galvanized piping is about 40–50 years,<ref>{{Cite web|last=Biard & Crockett|date=2016-05-16|title=How Long Will My Galvanized Pipes Last?|url=https://www.bcpsi.com/galvanized-pipes/|access-date=2021-02-06|website=Biard & Crockett}}</ref> but it may vary on how well the pipes were built and installed. Pipe longevity also depends on the thickness of zinc in the original galvanizing, which ranges on a scale from G01 to G360.<ref>{{Cite web|last=American Galvanizers Association|date=|title=Zinc Coatings|url=http://courtgalvanizinginc.com/wp-content/uploads/2012/04/Zinc_Coatings.pdf|archive-url=|archive-date=|access-date=|website=courtgalvanizinginc.com}}</ref> | In the early 20th century, galvanized piping swiftly took the place of previously used [[Cast iron pipe|cast iron]] and [[Pipe (fluid conveyance)#Materials|lead]] in [[Tap water|cold-water]] [[plumbing]]. Galvanized piping rusts from the inside out, building up layers of plaque on the inside of the piping, causing both water pressure problems and eventual pipe failure. These plaques can flake off, leading to visible impurities in water and a slight metallic taste. The life expectancy of galvanized piping is about 40–50 years,<ref>{{Cite web|last=Biard & Crockett|date=2016-05-16|title=How Long Will My Galvanized Pipes Last?|url=https://www.bcpsi.com/galvanized-pipes/|access-date=2021-02-06|website=Biard & Crockett}}</ref> but it may vary on how well the pipes were built and installed. Pipe longevity also depends on the thickness of zinc in the original galvanizing, which ranges on a scale from G01 to G360.<ref>{{Cite web|last=American Galvanizers Association|date=|title=Zinc Coatings|url=http://courtgalvanizinginc.com/wp-content/uploads/2012/04/Zinc_Coatings.pdf|archive-url=|archive-date=|access-date=|website=courtgalvanizinginc.com}}</ref> | ||
=== Automotive === | |||
In the case of [[automobile]] bodies, where additional decorative coatings of paint will be applied, a thinner form of galvanizing is applied by [[Electrogalvanization|electrogalvanizing]]. Electrogalvanized [[sheet steel]] is often used in automotive manufacturing to enhance the corrosion performance of exterior body panels; this tends to achieve lower coating thicknesses of zinc compared to hot-dip galvanization. | |||
== See also == | == See also == | ||
Latest revision as of 16:30, 5 November 2025
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Galvanization (also spelled galvanisation)[1] is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are coated by submerging them in a bath of hot, molten zinc.[2]
Galvanized steel is widely used in applications where corrosion resistance is needed without the cost of stainless steel, and is considered superior in terms of cost and life-cycle. It can be identified by the crystallization patterning on the surface (often called a "spangle").[3]
Galvanized steel can be welded; however, welding gives off toxic zinc fumes. Galvanized fumes are released when the galvanized metal reaches a certain temperature. This temperature varies by the galvanization process used. In long-term, continuous exposure, the recommended maximum temperature for hot-dip galvanized steel is Template:Convert, according to the American Galvanizers Association. The use of galvanized steel at temperatures above this will result in peeling of the zinc at the inter-metallic layer.[4]
Like other corrosion protection systems, galvanizing protects steel by acting as a barrier between steel and the atmosphere. However, zinc is a more electropositive (active) metal in comparison to steel. This is a unique characteristic for galvanizing, which means that when a galvanized coating is damaged and steel is exposed to the atmosphere, zinc can continue to protect steel through galvanic corrosion (often within an annulus of 5 mm, above which electron transfer rate decreases).
History and etymology
The process is named after the Italian physician, physicist, biologist and philosopher Luigi Galvani (9 September 1737 – 4 December 1798). The earliest known example of galvanized iron was discovered on an Indian armour in the Royal Armouries Museum collection in the United Kingdom, known from inscriptions to be earlier than the 1680s[5]
The term "galvanized" can also be used metaphorically of any stimulus which results in activity by a person or group of people.[6]
In modern usage, the term "galvanizing" has largely come to be associated with zinc coatings, to the exclusion of other metals. Galvanic paint, a precursor to hot-dip galvanizing, was patented by Stanislas Sorel, of Paris, on June 10, 1837, as an adoption of a term from a highly fashionable field of contemporary science, despite having no evident relation to it.[7]
Principle
The zinc coating, when intact, prevents corrosive substances from reaching the underlying iron.[8] Its main function is to act as a sacrificial anode to prevent the iron from rusting by cathodic protection. Zinc is more reactive than iron, so the zinc coating preferentially oxidizes to zinc carbonate, preventing the iron from corroding, even if there are gaps in the zinc coating. Additional electroplating such as a chromate conversion coating may be applied to provide further surface passivation to the substrate material.[9]
Corrosion
Galvanized steel can last for many decades if other supplementary measures are maintained, such as paint coatings and additional sacrificial anodes. Corrosion in non-salty environments is caused mainly by levels of sulfur dioxide in the air.[10]
Methods
Hot-dip galvanizing deposits a thick, robust layer of zinc iron alloys on the surface of a steel item. The hot-dip process generally does not reduce strength to a measurable degree, with the exception of high-strength steels where hydrogen embrittlement can become a problem.[11]
Galvanization can be done using electricity in electrogalvanization.
Sherardizing provides a zinc diffusion coating on iron- or copper-based materials.[12][13]
Common use
Construction steel
This is the most common use for galvanized metal; hundreds of thousands of tons of steel products are galvanized annually worldwide. In developed countries, most larger cities have several galvanizing factories, and many items of steel manufacture are galvanized for protection. Typically these include street furniture, building frameworks, balconies, verandahs, staircases, ladders, walkways, and more. Hot dip galvanized steel is also used for making steel frames as a basic construction material for steel frame buildings.[14]
Piping
Script error: No such module "Labelled list hatnote". In the early 20th century, galvanized piping swiftly took the place of previously used cast iron and lead in cold-water plumbing. Galvanized piping rusts from the inside out, building up layers of plaque on the inside of the piping, causing both water pressure problems and eventual pipe failure. These plaques can flake off, leading to visible impurities in water and a slight metallic taste. The life expectancy of galvanized piping is about 40–50 years,[15] but it may vary on how well the pipes were built and installed. Pipe longevity also depends on the thickness of zinc in the original galvanizing, which ranges on a scale from G01 to G360.[16]
Automotive
In the case of automobile bodies, where additional decorative coatings of paint will be applied, a thinner form of galvanizing is applied by electrogalvanizing. Electrogalvanized sheet steel is often used in automotive manufacturing to enhance the corrosion performance of exterior body panels; this tends to achieve lower coating thicknesses of zinc compared to hot-dip galvanization.
See also
- Electroplating
- Aluminized steel
- Cathodic protection
- Corrugated galvanized iron
- Galvanic corrosion
- Galvannealed – galvanization and annealing
- Prepainted metal
- Rust
- Rustproofing
- Sendzimir process
- Sherardizing
- Corrosion
- Sacrificial metal
- Corrosion engineering
References
External links
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- ↑ ZINC COATINGS OF INDIAN PLATE AND MAIL ARMOUR. Summary of XRF analysis conducted in September 1999 by the Royal Armouries Museum in Leeds and written up as part of a thesis by Helen Bowstead Stallybrass at the Department of Archaeological Sciences, Bradford University.
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