**3. Corrosion definition**

The spontaneous oxidation of metal is termed as corrosion [12], that is, Corrosion is the deterioration or destruction of metals and alloys in the presence of an environment by chemical or electrochemical means. The medium in which the metal undergoes corrosion is termed as corrosive or aggressive medium. Corrosion products formed are chemical compounds containing the metal in the oxidized form with the exception of gold and platinum, all other metals corrode and transform themselves into substances similar to the mineral ores from which they are extracted [13].
