Possible Distribution of Potential Inside Corroding Crevices

Abstract

In this paper, the case when the potential distribution inside a corrosion cavity obeys Ohm's law is considered. Mathematically, the potential drop in the crevice is described by a Poisson-type equation with a non linear source term. It is shown that, in the general case, this problem has more than one solution, indicating that the potential and current distributions in the crevice depend not only on the metal potential, solution conductivity, and geometry of the crevice, but also on the history of crevice initiation. The absence of a unique solution of the charge transfer equation can explain the fact that both passive and active crevices with approximately equal geometrical parameters are often observed simultaneously on the same metal surface. It is further shown that, in the general case, it is impossible to neglect the potential drop in the external environment when quantitatively describing crevice corrosion.