XII Chemistry BIEK Topic - Tin Plating (Short Note)

Tin Plating (Short Note)
Definition
The art of coating a metal with tin is called Tin-Plating.

Those metals which are coated with tin are called tin-plated metals.




Purpose And Examples of Tin Plating
The purpose of tin plating is to protect metals from corrosion and food poisoning. Iron is often tin-plated to protect it from rusting. The common cooking oil containers are made of tin-plated iron. The household utensils of copper and brass are tarnished in moist air due to the formation of thin layer of oxides and carbonates of copper. These are poisonous, due to these problems, utensils are coated with tin.




Method of Tin Plating
Tin plating is carried out by the following methods.


1. Hot Dipping or Mechanical Method

In this method, clean iron or steel sheets are dipped in the bath of molten tin. A layer of tin accumulates on the iron sheet and it gets coated.


2. Electrolytic Method or Electro-Plating

This method is based on electrolytic process. An electrolytic cell is developed, which contains metals to be tin-plated as cathode and pure tin as anode. The electrolytic solution consists of salt of tin such as tin chloride or tin sulphate and an acid such as hydrochloric acid. On passing electric current through the electrolytic cell tin deposits on the metal sheet. Through this method a uniform layer of tin is coated on zinc.


3. Classical Method

In this method, the clean hot surface of a utensil is polished with tin metal with a rag. Copper and Brass utensils are tin-plated by this method. The utensils are heated and rubbed with ammonium chloride before they are tin plated. This is done to remove the oxide from the utensils.