The equilibrium electrochemical conditions within a localized corrosion cell on iron have been calculated using activity coefficients to take into account the high ionic concentrations which occur within the occluded corrosion cell. The calculations utilize Pourbaix's model that the stable solid phases within a corrosion pit, crevice, or stress‐corrosion crack are Fe, Fe 3 O 4 , and FeCl 2 · 4 H 2 O . The calculated equilibrium conditions are: E = − 0.385 V vs. NHE, p H = 5.2 , [ Fe + + ] = 4.5 moles / liter , and [ Cl − ] = 9.0 moles / liter . If the occluded corrosion cell is limited to atmospheric pressure conditions, the internal conditions are calculated to be: E = − 0.281 V vs. NHE, pH = 4.8 , [ Fe + + ] = 4.5 moles / liter , and [ Cl − ] = 9.0 moles / liter . With both sets of results, the internal p H is only slightly higher and the electrode potential slightly more negative than in the original Pourbaix calculations. Thus, the calculated results support the basic ideas first proposed by Pourbaix.
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E. McCafferty (1981) studied this question.