Surface Area Dependence of Pitting Potential

Toshio Shibata
1982 Corrosion engineering digest  
Surface area dependence of pitting potential has been examined for SUS 304L stainless steel in 3.5% NaCI solution at 35C, using a multichannel pitting corrosion testing apparatus. The experimental data was proved to obey the relation which was formulated based on a stochastic theory. The predicted relation between pitting potential and surface area is as follows: Em= (VJSka)1/2+Ecrit, where Em is the most probable value of pitting potentials measured by the potential sweep velocity of V for the
more » ... surface area of S, k and t are constants, and Eerit is a critical pitting potential under which no probabliity of pit generation is expected. Thus the theory and experimental data demonstrate that the pitting potential decreases with increase in the surface area of specimen used, but approaches to the constant potential of ECrit at an infinite surface area. In this experiment, the numerical value of ka is so large that no significant surface area dependence is observed as far as a slow potential sweep velocity is used. But in other cases for different materials or environments, a small value of ka could be expected so that this surface area effect on the pitting potential could not be neglected.
doi:10.3323/jcorr1974.31.10_643 fatcat:ucuukjruk5ga7g7hvw5ypwbwx4