Oxygen diffusion, into crevice

The series of events leading to the formation of a severe crevice can be summarized in the following three stages. Firstly, crevice corrosion is believed to initiate as the result of the differential aeration mechanism mentioned earlier. IDissolved oxygen in the liquid which is deep in the crevice is consumed by reaction with the metal [Fig. 6.21( )]. Secondly, as oxygen diffusion into the crevice is restricted, a differential aeration cell tends to be set up between the... 

This adsorbed oxygen can then migrate across the surface or into the interior of the coal particle to a reactive site at which point it becomes chemically bound. The form of this chemical bond is phenolic-OH, carbonyl or peroxide type moieties. As the surface layers become saturated, the oxygen will diffuse deeper into the particles through pores and crevices to react with sites within the coal particle. This is the second, slower part of the adsorption process. At some point the chemical potential against diffusion into the particle becomes great enough that the oxidation from the exterior of the particle ceases. This point will be determined by the porosity of the coal and the temperature at which the oxidation is carried out. As... 

CORROSION, OXYGEN DEFICIENCY - A form of crevice corrosion in which galvanic corrosion proceeds because oxygen is prevented from diffusing into the crevice. 

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