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Is electroplating happen only with the help of a solution and what is the role of battery in it ?
Electroplating is often also called "electrodeposition", and the two terms are used interchangeably. As a matter of fact, "electroplating" can be considered to occur by the process of electrodeposition. Electrodeposition is the process of producing a coating, usually metallic, on a surface by the action of electric current. The deposition of a metallic coating onto an object is achieved by putting a negative charge on the object to be coated and immersing it into a solution which contains a salt of the metal to be deposited (in other words, the object to be plated is made the cathode of an electrolytic cell). The metallic ions of the salt carry a positive charge and are thus attracted to the object. When they reach the negatively charged object (that is to be electroplated), it provides electrons to reduce the positively charged ions to metallic form. Figure 1 is a schematic presentation of an electrolytic cell for electroplating a metal "M" from an aqueous (water) solution of metal salt "MA".

To further illustrate the foregoing, let us assume that one has an object made of one of the common metals, like copper, and that it has been properly pre-cleaned. We should want to plate it with, say, nickel. A wire will have to be attached to the object while the other end of the wire should be attached to the negative pole of a battery (or a power supply). To the positive pole of the battery (or power supply) we connect another wire with its other end connected to a rod made of nickel. Next we fill the cell with a solution of the metal salt to be plated. It is possible to use a molten salt and in some not so common cases, such as the deposition of tungsten, that is what is done. In most, more common, cases though the salt is simply dissolved in water. In our present example the nickel chloride salt dissociates in water to positively charged nickel cations and negatively charged chloride anions. As the object to be plated is negatively charged it attracts the positively charged nickel cations, and electrons flow from the object to the cations to neutralize them (to reduce them) to metallic form. Meanwhile the negatively charged chloride anions are attracted to the positively charged nickel rod (known as the anode of the electrolytic cell). At the anode electrons are removed from the nickel metal, oxidizing it to the nickel cations. Thus we see that the nickel dissolves as ions into the solution. That is how replacement nickel is supplied to the solution for that which has been plated out and one retains a solution of nickel chloride in the cell.

Plating cell


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