ZINC PLATING

Zinc Plating

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.

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.

The following are some benefits of Zinc Plating:

Excellent ductility and adhesion.
Excellent process to combat corrosion of steel.
Low stress deposit.
Excellent chromate conversion coating receptivity.
Zinc deposit appearance – comparable to chloride zinc or cyanide.
It operates within wide range of bath chemistry.
Contains no complexes or chelating agents.
It is suitable for either rack or barrel plating.
Temperature tolerance is up to 120?F – this helps reduce cooling costs.
Zinc coating does not undergo hydrogen embrittlement.

Zinc Plating - Benefits and Processes

Zinc plating has been around for quite some time giving a significant contribution most especially to the automotive industry. The people’s quest for a higher performance coating brought the development of this technology. Its use provides an excellent alternative to metal plating processes that involves toxic materials – like cadmium plating.

The Zinc Plating process:

Zinc plating is the process that involves electrolytic application of zinc to metal by immersing clean steel parts into a zinc salt solution and applying electric current into it. This immersion produces zinc coatings that prevent oxidation of the protected metal – zinc coating acts as a barrier and as a sacrificial anode when this barrier is damaged. Zinc is the best ally of steel to combat its natural enemy: corrosion.

ZINC PLATING PROCESS FLOW CHART

Digressing G & W Chemical
Rinse Stationary water
Pickling G & W Chemical 30% & 70% water
Rinse Stationary water
Chemical Dip Chemical Rinse
Rinse Stationary water
Zinc Plating Plating barrel/ vat process
Rinse DM water
Chemical Dip G & W Chemical 20%
Rinse DM water
Passivation As per customer req(yellow,black,blue,green,white)
Rinse DM water
Rinse DM water
Top Coat G & W Chemical
Drying Oven
Inspection Visual
Curing Open air
Despatch Sealing