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This Module consists of eight Web pages of required reading. The pagination is visible at the bottom of each page with direct links to adjacent pages.
Additional information can be found in sections 9.1 to 9.7 of the reference textbook (Corrosion Engineering: Principles and Practice).
Atmospheric corrosion is surely the most visible of all corrosion processes, e.g. rusty bridges, flag poles, buildings and outdoor monuments. The large segment of the paint industry committed to the manufacture and application of products for the protection of metals, as well as the large-scale operations of the galvanizing industry attest to the importance of controlling atmospheric corrosion.
Economic losses caused by atmospheric corrosion are tremendous and therefore account for the disappearance of a significant portion of metal produced. Consider, for instance, agricultural machinery, steel structures, fences, exposed metals on buildings, automobile mufflers or bodies, and the myriad of other metal items which are discarded when they become unusable as a result of corrosion. These constitute direct losses from corrosion.
Atmospheric corrosion has been reported to account for more failures in terms of cost and tonnage than any other type of material degradation processes. This particular type of material degradation has recently received more attention, particularly by the aircraft industry, since the Aloha incident in 1988, when a Boeing 737 lost a major portion of the upper fuselage in full flight at 7,300 m.
All of the general types of corrosion attack occur in the atmosphere. Since the corroding metal is not bathed in large quantities of electrolyte, most atmospheric corrosion operates in highly localized corrosion cells, sometimes producing patterns difficult to explain as in the example of this rusting galvanized roof.
Rusting galvanized roof with regular bands of rust
Thus, calculation of the electrode potentials on the basis of ion concentration, the determination of polarization characteristics, and other electrochemical operations are not as simple in atmospheric corrosion as they are in liquid immersion corrosion. However, all of the electrochemical factors which are significant in corrosion processes do operate in the atmosphere.
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See also CCE 513: Corrosion Engineering