Chapter3 - Basics and theories of corrosion: thermodynamics and electrochemistry

Abstract

Corrosion is a spontaneous process where highly energetic metallic structures get converted into their compounds forms through the chemical or electrochemical interactions with the constituents of the surrounding environment. Depending upon the environmental conditions, corrosion may be divided into wet or dry corrosion that occurs in the presence and absence of moisture, respectively. Obviously, wet corrosion which is also known as electrochemical corrosion occurs through electrochemical mechanism in the presence of moisture. Dry corrosion is also known as chemical corrosion as it takes place through chemical reaction between metallic structures and components of the environment. Chemical corrosion occurs in a moisture-free condition in the presence of corrosive gases, such as O2, SO2, CO2, H2S, H2, Cl2, NO2, F2, etc. Chemical corrosion taking place in the presence of oxygen is known as oxidative corrosion. Both electrochemical and chemical corrosion is greatly affected by numerous factors including the presence of salts and temperature. Generally, every 10°C rises in temperature results in an increase of corrosion rate by two times.