ABSTRACT
Corrosion of a metal or an alloy is an electrochemical reaction, in the sense that it involves transfer of charge (electrons) between a metal electrode and a chemical species. This process results in a decrease in free energy, and a change in free energy (ΔG) may be related to the potential of the corroding metal by the equation,
ΔG = −nEF (2.1)
where n is the number of electrons involved in the reaction, F is the Faraday constant (96,500 C/mol), and E is the electrode potential of the corroding metal/metal ion or salt system. It is caused mostly by heterogeneity on a metallic surface because of lower oxygen concentration or stresses or contact between dissimilar metals. It is essential, therefore, to understand the electrochemistry of corrosion and electrode kinetics. The basic concepts of electrochemical corrosion are discussed in this chapter. However, complex mathematical treatment is avoided and the concepts are presented in a manner to serve the purpose of this book.
