WHAT IS PLATING?

Plating is a process of covering a conductive surface by depositing a metal liquid. It is used as a corrosion resistance, to improve to solder-ability, to harden, to improve wearability, to reduce friction, to improve paint adhesion, to alter conductivity, to improve IR reflectivity, for radiation shielding.

There are various method of plating

1.Electroplating: It is a process of covering one metal onto another metal, most commonly used for corrosion resistance. In electroplating, an ionic metal is supplied with electrons to form a non-ionic coating on a substrate. A common system involves a chemical solution with the ionic form of the metal, an anode (positively charged) which may consist of the metal being plated (a soluble anode) or an insoluble anode (usually carbon, platinum, titanium, lead, or steel), and finally, a cathode (negatively charged) where electrons are supplied to produce a film of non-ionic metal. 

 

2.Electroless plating: It is also know as chemical plating as it include several simultaneous reaction in aqueous solution, which occur without the use of external power source.The reaction is accomplished when hydrogen is released by a reducing agent, normally sodium hypophosphite (Note: the hydrogen leaves as a hydride ion) or thiourea, and oxidized, thus producing a negative charge on the surface of the part.

Each of the method are used for Plating various metal onto another metal. The common types of plating are:

1.Gold plating: It is a method of depositing a thin layer of gold on the surface of glass or metal, most often copper or silver. Typically used for plating jewelries and electronics circuit.

2.Silver plating: It refers to  depositing a thin layer of Silver on the surface of glass or metal, most often copper or silver.The most common usage of silver plating is for ornamentation of jewelry, plates, cups, trophies and medals. The process adds a perfect polish to the surface on which the plating is done.

3.Zinc plating: Here the conductive surface is coated with a thin layer of zinc metal. It 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.

4. Nickel plating: Here thin layer of nickel is used to cover the conductive surface. Nickel is plated for many reasons. It provides a decorative appearance due to its ability to cover imperfections in the basis metal (leveling). Nickel deposits can be made brilliant and, when covered by a thin layer of decorative chromium, will maintain their brilliance even under severe conditions.

5.Chrome plating: Chrome plating is a finishing treatment using the electrolytic deposition of chromium. The most common form of chrome plating is the thin, decorative bright chrome, which is typically a 10-µm layer over an underlying nickel plate. When plating on iron or steel, an underlying plating of copper allows the nickel to adhere. The pores (tiny holes) in the nickel and chromium layers work to alleviate stress caused by thermal expansion mismatch but also hurt the corrosion resistance of the coating. Corrosion resistance relies on what is called the passivation layer, which is determined by the chemical composition and processing, and is damaged by cracks and pores. In a special case, micropores can help distribute the electrochemical potential that accelerates galvanic corrosion between the layers of nickel and chromium. Depending on the application, coatings of different thicknesses will require different balances of the aforementioned properties. Thin, bright chrome imparts a mirror-like finish to items such as metal furniture frames and automotive trim. Thicker deposits, up to 1000 µm, are called hard chrome and are used in industrial equipment to reduce friction and wear