Because the reaction rates of industrial metals with common gases are low at room temperature, gaseous corrosion, generically called oxidation, is usually an industrial problem only at high temperatures when diffusion processes are dominant. Forms of Corrosion Over the years, corrosion scientists and engineers have recognized that corrosion manifests itself in forms that have certain similarities and therefore can be categorized into specific groups. However, many of these forms are not unique but involve mechanisms that have over lapping characteristics that may influence or control initiation or propagation of a specific type of corrosion. This classification of corrosion was based on visual characteristics of the morphology of attack. Localized biological corrosion Metallurgically influenced corrosion Intergranular corrosion Dealloying corrosion Mechanically assisted degradation Erosion corrosion Fretting corrosion Cavitation and water drop impingement Corrosion fatigue Environmentally induced cracking Stress-corrosion cracking Hydrogen damage Liquid metal embrittlement Solid metal induced embrittlement General Corrosion .
General corrosion is defined as corrosive attack dominated by uniform thinning.
Localized Corrosion . The forms of corrosion under this category need no explanation, even though other forms could be placed in this category. It should be noted, however, that localized biological corrosion often causes or accelerates pitting or crevice corrosion. Metallurgically influenced corrosion was so classified as a result of the significant role that metallurgy plays in these forms of attack. It is well understood that metallurgy is important in all forms of corrosion, but this classification is meant to emphasize its role in these specific forms of attack.