Classical mechanism, of hydrogenation

The mechanism may change from acids to alkalis in some cases [365], This may be related to the higher sensivity of the Fe surface to oxidation in alkaline solutions [365, 367], Actually, the corrosion of Fe proceeds also under moderate cathodic load [368]. Impedance measurements have suggested that the classical mechanisms of hydrogen evolution is probably inadequate to describe the situation on Fe [377], A surface diffusion step with spillover of hydrogen to sites with lower M-H energy has been suggested. Adsorption of CN- interferes with such a diffusion. 

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