The metals produced by various reduction processes are not very pure.
They contain impurities, which must be removed to obtain pure metals.
The most widely used method for refining impure metals is electrolytic refining-the process of removal of impurities to get pure metal using electricity is known as electrolytic refining
In this process, the impure metalis made the anode and a thin strip of pure metal is made the cathode.
A solution of the metal salt is used as an electrolyte.
electrolytic refining of copper
On passing the current through the electrolyte, the pure metal from the anode dissolves into the electrolyte.
An equivalent amount of pure metal from the electrolyte is deposited on the cathode.
The soluble impurities go into the solution, whereas,
the insoluble impurities settle down at the bottom of the anode and are known as anode mud.
CORROSION
The surface of some metals, such as iron, is corroded when they are exposed to moist air for a long period of time.
This phenomenon is known as corrosion.
corrosion of iron also known as rusting of iron
PREVENTION FROM CORROSION
Paint
Oil or grease
Plastic coating
Tin plating – cover metal by molten tin
Electroplating
chrome plating
anodizing – protect metal by formation of thick metal oxide coating of generallyaluminium
making alloys
Galvanization – cover metal by molten zinc
Galvanization is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc.
galvanized steel protected from rust
The galvanized article is protected against rusting even if the zinc coating is broken.