Zinc Plating

Definition - What does Zinc Plating mean?

Zinc plating is the process of covering substrate metals (like steel and iron, etc.) with a layer or coating of zinc to protect the substrate from corrosion.

Corrosionpedia explains Zinc Plating

Zinc plating is primarily used to protect metals from corrosion effects. Zinc coatings prevent corrosion of protected metal by forming a physical barrier and acting as a sacrificial anode - even when this barrier is damaged. Zinc and iron/steel are joined and placed in an electrolyte; a cell is formed, in which the zinc becomes the anode and the steel the cathode. Then, the zinc is sacrificed, and the steel does not rust.

When exposed to the atmosphere, zinc reacts with oxygen, forming zinc oxide, which further reacts with water molecules in the air to form zinc hydroxide. In turn, zinc hydroxide reacts in the atmosphere with carbon dioxide to yield a thin, impermeable, tenacious and quite insoluble dull gray layer of zinc carbonate, which adheres to the underlying zinc, further protecting it from corrosion.

There are a number of methods used to apply zinc coatings, and each determines the coating’s thickness and ultimate durability in specific environments. The most commonly encountered types of zinc coatings are as follows:
  • Zinc electroplating
  • Mechanical plating
  • Continuously galvanized sheet
  • Thermal diffusion galvanizing
  • Galvanized pipe and tube
  • General or hot dip galvanizing
  • Zinc metal spraying
Zinc-coated or galvanized steel offers a unique combination of properties unmatched by any other material. These include:
  • High strength
  • Formability
  • Light weight
  • Corrosion resistance
  • Recyclability
  • Low cost
In the automotive industry, zinc plating is used as a cost-effective method to protect key components, such as brake calipers, brake pipes and power steering. Many zinc plating processes have been used extensively for heavy electrical transmission components. Zinc plating is also found in the manufacturing of tanks and armored personnel carriers.

Zinc should not be used on critical steel parts that can reach temperatures of 500"F or higher, as zinc has the ability to embrittle the steel by diffusing into grain boundaries. Zinc coatings can produce bulky corrosion products during exposure to marine or tropical environments and should not be used where the products may cause binding and prevent functioning of equipment with moving parts in contact. Rapid zinc corrosion can occur in confined atmospheres where repeated moisture condensation is likely and where there is an accumulation of certain organic vapors containing halogen.

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