In the case of cathodic control (activation control), the corrosion rate is given by
Where K1 is the specific rate constant of cathodic reaction, C is the concentration of the adsorbed water molecules in the Eyring's prototropic process, 1>α >0 and E is the natural eletrode potential. In the case of ``mixed control'' (where the cathode reaction is controled by activation process and the anode reaction is controled by diffusion process), the corrosion rate has no dirrect connection with the natural electrode potential and is a function of pH and the standard electrode potential of metal.
where n is the valency of the metal ions and EM0 is the standard electrode potential of metal. The heat of activation in the cathode reaction is one of the most important factors of the corrosion reaction and is calculated by the following equation.
|Δ H=1380 (2.1-log i-8.4V) (25°)|
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