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Chemistry Related to the Electroplating Process

Electroplating is the process of electrochemically attaching two metals to one another. According to the University of Wisconsin at Madison, electroplating is achieved via the electrolysis of two electrochemically active metals. Electroplating follows chemical principles and occurs by means of chemical reactions that take place in electrochemical cells. Many common metals, such as aluminum, iron, zinc and copper, can be used in these cells, which are connected by an ion-transfer mechanism and a conductive wire. These cells normally produce electric current that leaves the system and can be used to power electronic devices, but if electric current is added to the system, the normal behavior of the electrochemical cell reverses -- causing metal atoms to plate out on one of the metals in the system, which then forms a coating over the substrate material.

Oxidation and Reduction in Chemistry
- Oxidation-reduction, or ox-redox, is a reaction in which electrons are transferred from one metal to another in an electrochemical cell. Electroplating occurs only as part of an ox-redox cycle in an electrochemical cell. When two metal plates are separately suspended in aqueous solutions, each of which contains the same metal as the plate it surrounds, and are then connected by an ion bridge and conductive wire, an electrochemical cell is formed. Different electron affinities between the two metals cause one to be reduced and the other to be oxidized. The reduced metal gains electrons, and the oxidized metal loses them. This transmission of electrons generates current.
Electrolysis and Electroplating
- In an electrochemical cell, energy is added to reverse the direction in which the electrons flow and swaps the roles of the oxidizing and reducing metals in the system. The metal to be electroplated onto the surface of a substrate material can be dissolved in the aqueous solution surrounding the substrate. The added energy and electron flow cause the metal in solution to plate out onto the substrate metal.
Metals Used in Electroplating
- A number of metals can be electroplated onto a base material to alter the chemical resistance or behavior of the finished product. In galvanization, a rust-resistant metal, such as nickel, is electroplated onto a more vulnerable metal, like iron. Nails are routinely galvanized to prevent their degradation in a moist atmosphere. Gilding, a similar process, allows an aesthetically attractive gold finish to be applied to a low-cost metal substrate.
Byproducts of Electroplating
- Electroplating often involves metals that are harmless when attached to a substrate but that pose a threat to human health when disposed of as a byproduct of the electroplating process. Cadmium is often electroplated onto ships to help prevent friction from reducing hull performance; however, it is also a known carcinogen, and environmental release of cadmium is hazardous. Chromium, similarly toxic under certain circumstances, is often electroplated onto a cheaper substrate to provide the familiar chrome finish.

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