On the commercial scale, zinc electroplating is done
by the following steps.
- Surface of the metal is cleaned in alkaline detergent type solutions,
and it is treated with acid, in order to remove any rust or surface
scales. Cleanliness is essential for successful zinc electroplating, as
the molecular layers of oil or rust can prevent adhesion of the coating.
- Next, the zinc is deposited on the metal by immersing it in a
chemical bath containing dissolved zinc. A DC current is applied, which
results in zinc being deposited on the cathode. Alkaline zinc baths are
used by the finished products, to produce a more consistent zinc
thickness, especially in recesses.
- Hence an increased protection from corrosion is provided, as the
corrosion of the deposited zinc is reduced. The zinc coating can
increase the time required for the formation of white rust, by ten
times. Finished Products also apply sealers, which are now commonly
being specified by the automotive industry, further increasing corrosion
protection.
It is very difficult to obtain a uniform thickness of coating, with
electroplating technique. The thickness of the coating is very much
dependent on the geometry of the object being plated, and it is
preferentially on the external corners and protrusions of the metal body,
hence not much of it is deposited on internal corners and recesses. Zinc
electroplating process is used to make a clean, smooth and corrosion
resistant surface. It also makes an excellent undercoat for powder coating
or paint and can leave recesses on complex shaped components without
sufficient zinc coating, in order to provide corrosion protection.
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