Question

write four factors which increases the rate of corrosion and write four methods to protect metal against corrosion

Answer 1

Corrosion can be prevented if the metal is coated with something which does not allow moisture and oxygen to react with it.
Coating of metals with paint, oil, grease or varnish prevents the corrosion of metals.
Coating of corrosive metals with non-corrosive metals also prevents corrosion. Some of the methods by which metals can be coated with non-corrosive metals are:
Galvanizing: It is process of giving a thin coating of zinc on iron or steel to protect them from corrosion. Iron is galvanized by dipping it in molten zinc. It is then taken out and allowed to cool. Galvanizing is an effective methods of protecting steel because even if the surface is scratched, the zinc still protects the underlying layer.
Tinning: It is the process of giving a coating of tin, i.e., molten tin. Cooking vessels, made of copper and brass get a greenish coating due to corrosion. This greenish coating is poisonous. Therefore they are given a coating of tin to prevent corrosion.
Electroplating: In this method of a metal is covered with another metal using electrolysis. Silver-plated spoons, gold-plated jewelry, etc, are electroplated.
Anodizing: In this method metals like copper and aluminum are electrically coated with a thin strong film of their oxides. This film protects the metals from corrosion.
Alloying: Corrosion can be also prevented by alloying some metals with other metals. The resultant metals called alloys do not corrode easily, e.g. stainless steel.