Initiation and Propagation of Corrosion

The present paper is directed mainly at the question of water permeability through plasma films, the presence of water at a surface being considered essential for the Initiation and propagation of corrosion processes. 

Digby Macdonald and Leo Kriksunov provide a broad perspective on the complex phenomena by which fluid flow influences the initiation and propagation of corrosion in pits and cracks. By focusing on the industrially important environment of high temperature aqueous systems, the authors provide an important link between theoretical understanding, well-designed experiments, and predictive capability. 

Duquette, D. J., Mechanisms of crack initiation and propagation in corrosion fatigue , Proc. Int. Conf. on Mechanisms of Environmental Cracking in Materials, University of Surrey, 4-7 April 1977, The Metals Society, pp. 305-21 (1977)... 

The permeation coefficients of the two thin film materials differ by an order of magnitude. To the extent then, that water initiates and propagates the corrosion of metal substrates, plasma films of... 

The filament occurs on metals covered by an organic film and because of a certain discontinuity in the film, air and water penetrate through the coating and reach the underlying metal. This adjacent humid layer becomes saturated or rich in corrosive ions from soluble salts, and forms the zone called the active head of the filament. The dissolution of metal decreases as the solubility of the oxygen increases. The metallic ions oxidize and form compounds or corrosion products. These zones are called tails. Figure 6.22 illustrates a section and explains the mechanism of initiation and propagation of the filament. 

The term SCC can be defined as the initiation and propagation of cracks in a metallic component as a result of the combined influence of a mechanical stress and a specific corrosive environment . The stresses involved may be externally applied working stresses or internal residual stresses (often produced by deformation... 

Evolution of atomic hydrogen on the steel surface may provoke the initiation and propagation of cracks starting from the metal surface, especially in the presence of notches or localised corrosion attack. Even in the absence of flaws on the surface, atomic hydrogen may penetrate the steel lattice, accumulate in the areas subjected to the highest tensile stress, above all at points corresponding to lattice defects, and lead to brittle failure beginning at one of these sites. 

Potential control can be effective in suppressing the initiation and propagation of crevice corrosion. The electrochemical... 

Pitting cavities may fill with corrosion products and form caps over the pit cavities sometimes creating nodules or tubercles (Fig. 6.10). While the shapes of pits vary widely (Fig.6.11) they are usually roughly saucer-shaped, conical, or hemispherical for steel and many associated alloys. The following are some factors contributing to initiation and propagation of pitting corrosion ... 

Many mathematical models have been developed to simulate the initiation and propagation of crevice corrosion processes as a function of external electrolyte composition and potential. Such models are deemed to be quite important for predicting the behavior of otherwise benign situations that can progress into serious corrosion situations. 

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