Corrosion Mechanism

There are two basic mechanisms by which metals in electrolytes corrode

• Electrolytic Corrosion
• Galvanic Corrosion

Electrolytic corrosion is a result of direct current from outside sources entering and then leaving a particular metallic structure by way of the electrolyte. Where current enters the structure, that part is usually unaffected or is provided with some degree of protection. Where current leaves the structure, corrosion occurs. In underground work, this type of corrosion is often referred to as stray current corrosion and results from currents entering the soil from sources of DC such as electric railway systems or DC machinery.

Galvanic corrosion is self-generated activity resulting from differences in energy levels or potentials which develop when metal is placed in an electrolyte. These differences can arise from the coupling of dissimilar metals, variations in the electrolyte, non-homogeneity of the metal, or a combination of the above.

Source:www.bushman.cc/pdf/corrosion_theory.pdf