What is Electroplating Process ?

The process by which a metal is layered with some other metal by utilizing the process of hydrolysis is known as electroplating. The main purpose of the electroplating process is to provide a coating to prevent the corrosion of the metal. The electroplating is done by the process of oxidation. The electroplating like in case of chromium, a chromium layer is formed on the surface of other metal to protect or to decorate the metals. The electroplating is done in a container or apparatus in which the liquid solution is present known as brine along with the electrodes and clips to complete the process. To do the electroplating the current is passed through this solution.

Anode and Cathode

The process of electroplating includes two chemical process oxidation and the reduction. There are the two types of electrodes that are present in the electroplating apparatus known as the anode and the cathode, the anode is positive connected to the positive terminal of the supply and the cathode is connected to the negative terminal of the supply. The process of reduction take place at the cathode and the process of the oxidation takes place at the anode electrode.

The reduction state includes the gaining of the electrons on the surface of cathode while the oxidation process includes the reduction of the electrons at the anode. The metal at the anode is dissolved and shifted to the cathode through the solution called electrolyte solution. For the process the type of supply used is DC only.

The diagram for basic electroplating apparatus is shown in Figure below.

Diagram shows the basic electroplating process with anode and cathode

How does electroplating process work?

In electroplating an electrolyte solution is obtained that is a form of molten salt of the same material whose electroplating is to be obtained. The electrolyte solution has both positive and the negative ions. There are two electrodes present known as anode and cathode. The electrodes are connected externally with the power source, with anode connected to the positive terminal and cathode to the negative one.

As soon the power is turned on the current start flowing from the anode to to the cathode through the electrolyte solution. The positively charged ions in the electrolyte moves and reach the cathode. The ions at the cathode combine with the electrons and becomes negatively charged.

The negative ions on the other side reach to the anode and loose the electrons thus becoming negatively charged. It must be noted that the negative ions are in abundance in the electrolyte as compared to the positive ions.

The diagram for copper electroplating process is shown in figure below.

Diagrams shows the electroplating of copper over a key along with the flow of positive copper ions towards the cathode.
Copper Electroplating

Chromium Electroplating

To know the process for electroplating consider the case of chromium electroplating. In this method of the electroplating, the chromium layer is used to protect another metal or alloy.

The electric current is passed through the electrolyte using the two cathodes. The electrolyte used is called the chromic acid. As the electroplating process continues the chromium atoms forms a electroplate layer on the alloy or the substrate. The electrodes that are used in the process have anode made of tin lead alloy. This alloy is used as an positive electrode and helps in maintaining the balance by re-oxidation of chromium into chromic acid.

Purpose of Electroplating

The electroplating is used to maintain the life of metal or alloy by coating a thin layer of some other material on to the surface that is to be protected.

  • The electroplating process create a layer of other material on the surface of the substrate to be protected, this smoothness the surfaces and prevent any sort of tarnishing, corrosion or wear and tear.
  • The electroplating process also uses a non-metallic coating to protect the surface from corrosion and make it corrosion resistance. The non-metallic electroplating is also used for molding the surface.
  • For decoration purpose electroplating is used like in automobiles as by electroplating the normal quality metal or alloy can be used to look as an expensive material. For example chromium finishing is used to provide a fine look of vehicles metal parts nowadays.
  • The electroplating is also used to increase the electrical conductivity of any metal. For example electroplate of a thin layer of copper on any conductor can increase its conductivity.
  • Electroplating help in increasing the heat tolerance capacity of a substrate as it provides a heat shield at the outer surface of material.

Context and Applications

In each of the expert exams for undergraduate and graduate publications, this topic is mainly used for

  • Bachelors of Chemical Engineering
  • Masters of Chemical Engineering
  • Production Engineering Applications

Electroplating is used in various industrial processes and has many applications in various fields such as:

  • Applications in paint shops like for cars and other metals for decorations.
  • Electroplating of food cans to protect them from rusting or decomposing with food.
  • Electroplating of marine ships as they are vulnerable to rust in sea water.
  • Used in mining industry for separation of ores and metals.
  • Rack Plating
  • Line Plating
  • Mass plating
  • Continuous Plating

Common Mistakes

  • Make sure that electroplate is on all the required area of the substrate.
  • There must be no peeling layer on the surface.
  • There must be no rough surfaces and the plating must be even.
  • Electroplating must not be under-thin or over thick it must be even.
  • In case of decoration the appearance must be pleasant.

Practice Problems

Q1. Electroplating is based in the principal of _________.

(a) Hydrolysis

(b) Pyrolysis

(c) Reserve Osmosis

(d) None of these

Correct option- (a)

Explanation: Electroplating works on hydrolysis problem.

Q2. Appearance of the metal can be enhanced by which of the electroplating.

(a) Chromium electroplating

(b) Tin electroplating

(c) Nickel Electroplating

(d) Copper Electroplating

Correct option- (a)

Explanation: Chromium plating is used to enhance the appearance as seen in vehicles.

Q3. The electrolyte is generally a salt solution.

(a) True

(b) False

Correct option-(a)

Explanation: True as the salt solution contains both positive and negative ions.

Q4. The thickness of the electroplate surface depends upon.

(a) Electrolyte density

(b) Time period of plating

(c) Electrode thickness

(d) None of the above

Correct option- (b)

Explanation: The thickness of the material deposited is directly proportional to the time for which plating is done.

Q5. What is the type of supply used in Electroplating.

(a) Alternating current

(b) Direct current

(c) Programmable power supply

(d) None of these

Correct option-(b)

Explanation: The power supply used in the electroplating is DC only.

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