6.5.4.1 Types of corrosion

Corrosion is a chemical reaction between a metal and its environment. This reaction alters the properties of the metal and can significantly impair the function of the metal, the environment or the technical system to which the metal belongs.
Due to their direct contact with the ground and moisture, earthing systems are exposed to various electrochemical attacks. The most common types of corrosion observed in connection with earthing systems include:

• Electrochemical corrosion 
  This occurs when metallic materials come into contact with an electrolyte (e. g. damp soil or groundwater). This causes the metal to gradually deteriorate through oxidation, resulting in general ageing and material weakening.