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.
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