Metals are to be surface-finished to obtain a smooth and finished surface. Smoothing of the surface is done in various ways such as lapping, honing, grinding, reaming, etc. It has many advantages but one major disadvantage is that it is highly porn to corrosion and get rust easily. So, to protect the finished surface from these effects, metal coating is done.
Metal coating is the process of surface finishing in addition to surface finishing operation. In the metal coating process, a layer of metal is coated or applied to the surface of an object normally called substrate or conductive surface to enhance certain properties of an object such as corrosion resistance, wear resistance, appearance, etc.
In this chapter, we will discuss the various metal coating processes. Among the various coating methods, electroplating and galvanizing processes are the most important. So, let us start with electroplating.
Electroplating
Electroplating is the process of plating one metal on another by hydrolysis, most commonly for decorative purposes or to prevent metal corrosion. It allows manufacturers to use inexpensive metals such as steel or zinc for most of the product and then apply different metals on the outside to account for appearance, protection, and other properties desired for the product. Various coatings are used such as nickel, copper, silver, chromium, zinc, etc., for electroplating.
Electroplating is widely used in automobile, airplane, electronics, jewelry, and toys industries. The overall process of electroplating uses an electrolytic cell, which consists of a negatively charged cathode (on which Plating is to be done), an electrolyte of metal salt, and a positively charged anode (plating metal). When these anode and cathode dip into an electrolyte and an electric current passes through it, the two metals are attracted to each other and plating is done.
There are various types of electroplating but we have to study only silver plating, chromium plating, and nickel plating.