Corrosion fatigue mechanisms, metallic materials

D.W. Hoeppner, Fretting fetigue and corrosion fetigue of metallic materials, in Corrosion Fatigue, Chemistry, Mechanics and microstructure, NACE, Houston, TX, 1972, pp. 3-10. 

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)... 

Below is a brief account of the mechanical aspect contribution into corrosive wear. Failure of materials is treated today as a discrete process of jerky local elementary acts repeated periodically in time [15]. Since metal friction has a pulse behavior and metals wear by the fatigue mechanism [16], so friction and wear in corrosion-active media should be treated as the interrelation of the process with adsorption and corrosive fatigue. Adsorption fatigue usually paves the way for corrosion processes in the materials and precedes stronger effects in the media where the rubbing bodies operate [17]. 

Since a frequently repeated minimum stress amplitude is needed to initiate corrosion fatigue in stainless steels in passivating solutions, it must be assumed that this load limit is connected with the mechanical stress capacity of passive layers. Only when particularly marked slip starts at one point on the surface will the layer be (racked. At that point, a constantly repetitive process begins, in which a new activation process at the same spot always follows repassivation. Each new passivation process consumes metal, deepens the corrosion, and increases the stress peak until, because of the constantly rising stress, repassivation is no longer possible. The resistance of passive metallic materials under fatigue conditions in electrolytes is therefore largely dependent on three factors ... 

Structural materials that are direcdy exposed, such as in cabinets, housings, and heat sinks, are fabricated fix>m materials such as steels, stainless steels, brass, zinc, aluminum, and other metals and alloys with appropriate prof>erties. The types of corrosion encountered in these structures depend on the environment and material as would be exp>ected. Both uniform and localized corrosion can be important when cosmetic corrosion is of concern. In structural applications, crevice corrosion, corrosion fatigue, stress corrosion cracking (SCC), galvanic corrosion, and intergranular corrosion causing reduction in mechanical properties are important. 

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