Prediction of pathways for the dissolution of iron

Previous mechanisms for the anodic dissolution of iron have been reviewed, and experimental evidence to distinguish between them is given. Of the various values found in the literature for the anodic Tafel slope, the values of 30 and 40 mV at (30°C) seem to be the most accurate. These two values have been taken as criteria for the possible mechanisms. New reaction pathways have been suggested which also involve the formation of Fe(OH)₂, FeOH⁺, and Fe₂OH⁺ as intermediates, and both the Tafel slope and the reaction order with respect to OH^? for these pathways have been deduced from steady state kinetics. The data thus obtained show that many of the proposed rate-determining steps give rise to the same results derived for previous mechanisms, thus indicating that such previous mechanisms are not the only possible ones. Difficulties associated with the work on iron, and with the present state of steady state kinetics are also outlined.