Hot-dip galvanizing


Hot-dip galvanizing

Hot-dip galvanizing is a form of galvanization. It is the process of coating iron or steel with a thin zinc layer, by passing the steel through a molten bath of zinc at a temperature of around 860 °F (460 °C). When exposed to the atmosphere, pure zinc reacts with oxygen to form zinc oxide, which further reacts with carbon dioxide to form zinc carbonate, a dull grey, fairly strong material that stops further corrosion in many circumstances, protecting the steel below from the elements. Galvanized steel is widely used in applications where rust resistance is needed, and can be identified by the crystallization patterning on the surface (often called a "spangle").

The process of hot-dip galvanizing results in a metallurgical bond between zinc and steel with a series of distinct iron-zinc alloys. The resulting coated steel can be used in much the same way as uncoated. Galvanized steel can be welded; however, one must exercise caution around the resulting zinc fumes. Galvanized steel is suitable for high-temperature applications of up to 392 °F (200 °C). Use at temperatures above this level will result in peeling of the zinc at the intermetallic layer. Galvanized sheet steel is commonly used in automotive manufacture to enhance corrosion performance of exterior body panels of some models.

Steel strip can be hot-dip galvanized in a continuous line. Hot-dip galvanized steel strip (also sometimes loosely referred to as galvanized iron) is extensively used for applications requiring the strength of steel and resistance to corrosion. Applications include: roofing and walling, safety barriers, handrails, consumer appliances and automotive body parts. One common use is in metal pails. They are also used in most heating and cooling duct systems in buildings

Individual metal articles, such as steel girders or wrought iron gates, can be hot-dip galvanized by a process called batch galvanizing. Other modern techniques have largely replaced hot-dip for these sorts of roles. This includes electrogalvanizing, which deposits the layer of zinc from an aqueous electrolyte by electroplating, forming a thinner and much stronger bond.

New Technology

ZQ - Dynamic Galvanizing® (GSI Technology, Inc. Cortland, OH 44410)

History

*1742: French chemist Paul Jacques Malouin describes, in a presentation to The French Royal Academy, a method of coating iron by dipping it in molten Zinc.
*1836: French chemist Stanislas Sorel obtains a patent for a means of coating iron with Zinc after first cleaning it with 9% sulfuric acid and fluxing it with ammonium chloride.

ee also

* Bolt manufacturing process
* Corrugated galvanised iron
* Liquid metal embrittlement
* Metal fume fever
* Plating
* Sendzimir process
* Surface finishing


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Look at other dictionaries:

  • hot (dip) galvanizing — Смотри горячее цинкование …   Энциклопедический словарь по металлургии

  • hot-dip coating — /hot dip / the process of coating sheets of iron or steel with molten zinc. Also called hot galvanizing. [1920 25] * * * …   Universalium

  • hot-dip coating — /hot dip / the process of coating sheets of iron or steel with molten zinc. Also called hot galvanizing. [1920 25] …   Useful english dictionary

  • hot-dip — noun A method of galvanizing iron or steal by passing it through a bath of molten zinc …   Wiktionary

  • galvanizing bath — A bath for hot dip galvanizing or electrogalvanizing …   Dictionary of automotive terms

  • galvanizing — Protection of iron or steel against exposure to the atmosphere and consequent rusting by application of a zinc coating. Properly applied, galvanizing may protect from atmospheric corrosion for 15–30 years or more. If the coating is damaged, the… …   Universalium

  • hot galvanizing. — See hot dip coating. * * * …   Universalium

  • hot galvanizing. — See hot dip coating …   Useful english dictionary

  • dry galvanizing — A hot dip galvanizing method in which the metal components are first immersed in a solution of flux and then dried, so that they become pre coated with a thin film of flux, which melts in the zinc bath, to which certain metals, such as tin and… …   Dictionary of automotive terms

  • spin galvanizing — A hot dip galvanizing process for small objects. The objects are immersed into the molten zinc in a perforated basket which, once the coating forms, is centrifuged at high speed so that the spinning action throws off the surplus zinc and ensures… …   Dictionary of automotive terms


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