We have heard of coating of one metal on another metal using the process of electrolysis. We have also heard about copper plating and silver plating in our daily lives. In this article, let us discuss in brief electrolysis and electroplating along with their applications.
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What is Electrolysis?
The word “electrolysis” was introduced by Michael Faraday in the 19th century. In chemistry, electrolysis is a method that uses a direct current (DC) to drive a non-spontaneous chemical reaction. This technique is commercially significant as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell.
We can define electrolysis as:
The process by which ionic substances are decomposed into simpler substances when an electric current is passed through them.
The fundamental process of electrolysis is the interchanging of ions and atoms by the addition or removal of electrons from the external circuit.
- Ionic compounds contain charged particles called ions. For example, Sodium Chloride contains positively charged Sodium ions and negatively charged chlorine ions.
- The ions must be free to move in order to start the electrolysis process. When an ionic substance is dissolved in water or melted then the ions are free to move. During electrolysis, positively charged ions move to the negative electrode and negatively charged ions move to the positive electrode. Then positively charged ions receive electrons and negatively charged ions lose electrons. Both the products of the dissociation get collected at the electrodes.
- For instance, if electricity is passed through molten sodium chloride, the sodium chloride is broken into sodium and chlorine, and they collect at their respective electrodes. The metals get precipitated and the gases escape. This ability to break down substance with a current is used in many ways.
- Electrolysis is widely used for electroplating.
Why is Aluminium no longer a precious metal?
In medieval times, aluminium was almost as precious as silver. Its extraction was not known and pure aluminium was extremely hard to come by. The application of electrolysis turned aluminium from a precious metal to one of the most largely used metals by humans. Aluminium is extracted from its ore by the process of electrolytic decomposition and deposition.
Uses of Electrolysis
- Electrolysis is done for coating one metal on another.
- The industrial use includes various metals such as aluminium, magnesium, chlorine, and fluorine etc.
What is Electroplating?
Electroplating is a process that uses an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode.
- Electroplating is a process that uses electric current to reduce dissolved metal ions by the use of electrolysis, to obtain the dissolved metal ions at the other electrode, mostly in the form of a uniform coating.
- It is the process of plating one metal onto another by hydrolysis, most commonly for decorative purposes or to prevent corrosion of metals.
- There are also specific types of electroplating such as copper plating, silver plating, and gold plating. It allows the manufacturers to make the product with economical materials and then coat the metals to add properties such as rust proofing, improving its appearance and improving its strength.
How does Electroplating work?
The positive electrode should be the metal that you want to coat the object with. The negative electrode will be the object that should receive the deposit of the electroplating metal. The electrolyte should be a solution of the coating metal, as it is a metal nitrate or sulphate. We can examine electroplating better with few examples;
The object that is to be plated is connected to the negative terminal of the power supply. A piece of silver is connected to the positive terminal. The electrolyte is a silver nitrate solution. This process can also be used to purify silver. We can take an impure block at the positive terminal and a strip of pure silver to the negative. The pure silver is deposited via electrolysis at the negative terminal leaving behind the impurities.
The object that is to be plated is connected to the negative terminal of the power supply. A piece of copper is connected to the positive terminal. The electrolyte is a copper Sulphate solution.
Like with silver plating, copper deposition can be used to purify copper. In this case, both the electrodes are made from copper. As the impure positive electrode gradually disappears leaving the impurities behind the negative electrode gradually gets coated with pure copper.
Difference Between Electrolysis and Electroplating
Following is the table explaining the difference between electrolysis and electroplating:
|Electrolysis refers to the breaking apart from a molecule by the means of the electrochemical reaction.||Electroplating refers to the passage of current through the solution with metal such that it gets deposited on one of the electrodes.|
|Electrolysis is good for carrying out the non-spontaneous chemical reactions.||Electroplating is good when metallic ions need to be coated on other metal.|
|Electrolysis is used for the extraction of metals from its ores.||Electroplating is used for coating metals on pure metals.|
|Finds applications in electrosynthesis, mercury cell process, and electrorefining.||Finds application in preventing metals from corrosion.|
Electrolysis of Water
Electrolysis of water is the decomposition of water into oxygen and hydrogen gas. This is achieved by passing an electric current through the water. Two electrodes are placed in the container with water. The electric current is passed through these electrodes. Stainless steel or platinum are used for the making of the electrodes.
The negatively charged electrode that is cathode is the place where the hydrogen will get accumulated while the positively charged electrode that is anode is the place where the oxygen will get accumulated.
Electrolysis of water is also an example of decomposition which is also known as electrolytic decomposition.
Frequently Asked Questions – FAQs
What is the principle behind electroplating?
Hydrolysis is the principle behind electroplating. For electroplating to take place, metal salt should be present in the aqueous solution. The end product of electroplating is water molecule. Thus, hydrolysis is the principle behind electroplating.
Mention the purposes of electroplating.
Following are the main purposes of electroplating:
- For protecting metals against corrosion
- To decorate the articles by giving them shiny appearances
- To fix the worn out materials
Define nickel strike.
Nickel strike is also known as flash layer and is defined as the process in which electric current is used to coat a conductive material along with a thin layer of nickel.
How many ions can be discharged during electrolysis?
During electrolysis, 2 out of 4 ions can be discharged during electrolysis.
Name the electrolyte used in lead-acid cell.
Dilute H2SO4 is the electrolyte that is used in lead-acid cell.
Name the metal that is purified using electrolysis.
Copper is the metal that is purified using electrolysis.
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