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Zinc plating
Zinc coatings prevent oxidation of the protected metal by forming a barrier and by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not cause a breakdown of the substrate's surface integrity as it is formed. Indeed the zinc oxide, if undisturbed, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminum and stainless steels by their oxide layers. Zinc plating is the most common, low cost; electroplated coating that is normally applied to ferrous components to give corrosion protection. The coating can be coloured to give gold; black or olive drab coatings by post treatment. The relatively low cost, protective nature and attractive appearance of zinc make it a popular coating for nuts, bolts, washers, metal stampings and automotive parts, such as interior components and gas filters. In addition, zinc serves as an effective undercoat for paints when high corrosion performance is required.
What Material Can Be Zinc Plated? Near any metal can be zinc plated but the most common are steel and iron on which it offers sacrificial protection.
How Is It Done? The commercial zinc electroplating process has three basic steps:
1. Cleaning the surface, which is normally done in alkaline detergent type solutions, followed by acid treatments to remove any rust or surface scale
2. Depositing zinc: The work is held on specially designed racks, immersed in a chemical bath containing dissolved zinc and a DC current is applied resulting in zinc being deposited on the work (cathode).
3. Post treatment: This provides increased corrosion protection to reduce the corrosion of the deposited zinc. These coating can increase the time to white rust by 10 fold with the yellow giving the best results.
Recommended uses for Zinc electroplating: Zinc plating is used where a clean, smooth, corrosion resistant surface is required. Commonly used on nuts, bolts, metal brackets. etc but it also makes an excellent undercoat for powdercoating or paint. Zinc electroplating can leave recesses on complex shaped components without sufficient zinc coating to provide corrosion protection.
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