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Galvanization

Galvanization or galvanisation refers to any of several electrochemical Electrochemistry

Electrochemistry is a branch of chemistry [i] that studies the reactions which take place at the interfa ... 

 processes named after the Italian scientist Luigi Galvani Luigi Galvani

Luigi Galvani was an Italian [i] physician [i] and physicist [i] who lived and died in Bologna [i] ... 

. # Originally, galvanization was the administration of electric shocks . It stemmed from Galvani's induction of twitches in severed frog Frog

The frog is an amphibian [i] in the order Anura . ... 

s' legs, by his accidental generation of electricity Electricity

Electricity is a general term for the variety of phenomena resulting from the presence and flow of electric charge [i] ... 

. This archaic sense is the origin of the meaning of galvanized when meaning 'stirred to sudden action'. Its claims to health benefits have largely been disproven, except for some limited uses in psychiatry. See also: Galvanism Galvanism

[i] [i] ... 

, Violet wand

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Encyclopedia

Galvanization or galvanisation refers to any of several electrochemical Electrochemistry

Electrochemistry is a branch of chemistry [i] that studies the reactions which take place at the interfa ... 

 processes named after the Italian scientist Luigi Galvani Luigi Galvani

Luigi Galvani was an Italian [i] physician [i] and physicist [i] who lived and died in Bologna [i] ... 

.
  1. Originally, galvanization was the administration of electric shocks . It stemmed from Galvani's induction of twitches in severed frog Frog

    The frog is an amphibian [i] in the order Anura . ... 

    s' legs, by his accidental generation of electricity Electricity

    Electricity is a general term for the variety of phenomena resulting from the presence and flow of electric charge [i] ... 

    . This archaic sense is the origin of the meaning of galvanized when meaning 'stirred to sudden action'. Its claims to health benefits have largely been disproven, except for some limited uses in psychiatry. See also: Galvanism Galvanism

    [i]

[i] ... 

, Violet wand

  1. Later the word was used for processes of electrodeposition. This remains a useful and broadly applied technology, but the term "galvanization" has largely come to be associated with zinc Zinc

    Zinc is a chemical element [i] in the periodic table [i] that has the symbol Zn and atomic number [i] ... 

     coatings, to the exclusion of other metals.
  2. In current use, it typically means hot-dip galvanizing, a chemical process that is used to coat steel Steel

    Steel is a metal [i] alloy [i] whose major component is iron [i], with carbon [i] content between 0.02% ... 

     or iron Iron

    Iron is a chemical element [i] with the symbol Fe and atomic number [i] 26. ... 

     with zinc. This is done to reduce corrosion Corrosion

    Corrosion is deterioration of intrinsic [i] properties in a material due to reactions with its environme ... 

      of the ferrous Iron

    Iron is a chemical element [i] with the symbol Fe and atomic number [i] 26. ... 

     item; while it is accomplished by non-electrochemical means, it serves an electrochemical purpose.


The remainder of the article is about zinc anti-corrosion coatings.

Zinc coatings prevent oxidation of the protected metal by forming a barrier, and by acting as a sacrificial anode if this barrier is damaged. Zinc oxide Zinc oxide

Zinc oxide is a chemical compound [i] with formula ZnO. ... 

 is a fine white dust that does not cause a breakdown of the substrate's surface integrity as it is formed. Indeed the zinc oxide, if undisturbed, can act as a barrier to further oxidation Redox

Redox reactions include all chemical processes [i] in which atoms have their oxidation number [i] ... 

, in a way similar to the protection afforded to aluminium Aluminium

Aluminium or aluminum is the chemical element in the periodic table that has the symbol Al ... 

 and stainless steel Stainless steel

In metallurgy [i], stainless steel is defined as a ferrous [i] alloy [i] with a minimum of 10% chromium [i] ... 

s by their oxide layers.

Hot dip galvanizing deposits a thick, robust layer that may be more than is necessary for the protection of the underlying metal in some applications. This is the case in automobile Automobile

An automobile is a wheel [i]ed passenger [i] vehicle [i] that carries its own motor [i]. ... 

 bodies, where additional rust proofing paint will be applied. Here, a thinner form of galvanizing is applied by electroplating Electroplating

Electroplating is the coating of an electrically conductive [i] object with a la ... 

, called "electro-galvanization". However, the protection this process provides is insufficient for products that will be constantly exposed to corrosive materials such as salt water. Nevertheless, most nails made today are electro-galvanized.

Galvanic protection can be achieved by connecting zinc both electronically and ionically . In such a configuration the zinc is absorbed into the electrolyte in preference to the metal that it protects, and maintains that metal's structure by inducing an electric current. In the usual example, ingots of zinc are used to protect a boat's hull and propellers, with the ocean as the common electrolyte.

As noted previously, both mechanisms are often at work in practical applications. For example, the traditional measure of a coating's effectiveness is resistance to a salt spray. Thin coatings cannot remain intact indefinitely when subject to surface abrasion, and the galvanic protection offered by zinc can be sharply contrasted to more noble metals. As an example, a scratched or incomplete coating of chromium Chromium

Chromium is a chemical element [i] in the periodic table [i] that has the symbol Cr and atomic number [i] ... 

 actually exacerbates corrosion of the underlying steel, since it is less electrochemically active than the substrate.



The size of crystallite Crystallite

A crystallite is a domain of solid-state matter that has the same structure as a single crystal [i].
... 

s in galvanized coatings is an aesthetic feature, known as spangle. By varying the number of particles added for heterogeneous nucleation Nucleation

Nucleation is the onset of a phase transition [i] in a small region. ... 

 and the rate of cooling in a hot-dip process, the spangle can be adjusted from an apparently uniform surface to grains several centimeters wide. Visible crystallites are rare in other engineering materials.

See also

  • Sherardising
  • Hot-dip galvanizing
  • Corrugated galvanised iron Corrugated galvanised iron

    Corrugated galvanised iron, commonly abbreviated [i] CGI, is a building material [i] compos...