Galvanizing is the process of covering a base metal (such as steel and iron, etc.) with a layer or coating of zinc to protect the base material from corrosion.
Galvanizing is primarily used to protect metals from corrosion. Zinc coatings prevent corrosion of the protected metal by forming a physical barrier and acting as a sacrificial anode—even if that barrier is compromised. The zinc and iron/steel are connected and placed in an electrolyte; forming a battery in which the zinc becomes the anode and the steel becomes the cathode. Then, the zinc is sacrificed and the steel does not rust.
When exposed to the atmosphere, zinc reacts with oxygen to form zinc oxide, which further reacts with water molecules in the air to form zinc hydroxide. Zinc hydroxide, in turn, reacts with carbon dioxide in the atmosphere to produce a thin, impermeable, tough, completely insoluble layer of dark gray zinc carbonate, which adheres to the underlying zinc, further protecting it from corrosion.
There are a variety of methods that can be used to apply zinc coatings, each of which determines the thickness of the coating and its ultimate durability in a particular environment. Common zinc coating types are as follows:
galvanized
mechanical plating
Continuous galvanized sheet
Thermal Diffusion Galvanized
Galvanized pipe and tube
Ordinary or hot-dip galvanized
Zinc Metal Spraying
Galvanized or galvanized steel offers a unique combination of properties unmatched by any other material. These include:
high strength
Formability
light
Corrosion resistance
Recyclability
low cost
In the automotive industry, galvanizing is used as a cost-effective method of protecting critical components such as brake calipers, brake pipes and power steering. A number of galvanizing processes are widely used for heavy electrical transmission components. Galvanizing is also found in the manufacture of tanks and armored personnel carriers.
Zinc should not be used on critical steel components where temperatures may reach 500"F or higher due to the ability of zinc to embrittle the steel by diffusing into the grain boundaries. Zinc coatings will generate significant corrosion products when exposed to marine or tropical environments and will not Should be used where product may cause binding and interfere with operation of equipment in contact with moving parts.Rapid zinc corrosion may occur in closed environments where repeated moisture condensation may occur and where certain organic vapors containing halogens accumulate.
