Galvanizing Coating for Protection

in Steel

Galvanized coating allows steel to survive against corrosive elements present in different environments: indoor and outdoor atmospheres, fresh water, sea water, soil, and even concrete.

In atmospheric environments, galvanized coating provides corrosion protection through the formation of zinc oxide. Zinc oxide is formed when zinc and atmospheric oxygen react, whereas zinc hydroxide is formed with the presence of moisture. Both zinc oxide and zinc hydroxide react with carbon dioxide in the air to form zinc carbonate, which provides the corrosive protection in galvanized coating.

Because its galvanized coating protects it from corrosion, galvanized steel can survive in five different conditions. Moderately industrial conditions include most city or urban area atmospheres which contain air emissions of sulfides and phosphates that cause corrosion. Suburban atmosphere conditions are less corrosive, and include residential areas. Temperate marine conditions relate to marine environments, where corrosion is greatly influenced by the wind direction and intensity. Tropical marine conditions are found in warmer climates and are less corrosive than temperate marine climates. Lastly, rural conditions have lower levels of air emissions compared with those situated in urban areas.

In liquids, the solution’s pH influences the coating performance of galvanized steel. Galvanizing performs well solutions with pH levels above 4.0 and below 12.5, which allow the coating to protect the steel by slowing corrosion to a low rate. It also protects steel government grade strapping in fresh water (all forms of water except sea water) exposure. Fresh water includes hot and cold domestic, industrial, river, lake, and canal waters.

Galvanizing also protects government steel strapping in sea water. Sea water contains a high level of chloride and dissolved salts (sulfides and chlorides) which cause zinc corrosion. Government steel strapping is also galvanized to protect it from corrosion in soil. Coarse and textured soils like gravel and sand allow air to circulate, causing atmospheric corrosion, whereas clay and silt soils have poor aeration and drainage, which cause corrosion similar to that of water. 

Galvanized steel that meet the standards of government suppliers needs corrosion protection in concrete. During construction, a steel wire or rebar is embedded in concrete to provide additional strength. The rebar is not visible, so it needs corrosion protection from galvanized coating. A galvanized rebar reduces cracking and adds strength in buildings.

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Carl Patten has 24 articles online

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Galvanizing Coating for Protection

This article was published on 2011/10/06