Modeling Particulates Effects on the Cathode Current Capacity in Crevice Corrosion

Abstract

The presence of particulates within thin electrolyte films covering the cathode in corroding systems affects the cathodic current distribution and the total current capacity. These effects are due to increased solution resistance (“volume effect”) and decreased available electrode area (“surface effect”) associated with the presence of the particulates. This work simulates and characterizes the effect of uniform particulate layers embedded within thin electrolyte films on the cathodic current capacity under steady-state conditions. Particulate configurations consisting of varying particle sizes, shapes, arrangements, volume fraction, and electrode coverage were numerically modeled. It is concluded that the effects associated with the particles can be fully accounted for in terms of two corrections: the decrease in the electrolyte conductivity due to volume blockage by the particles is correlated using Bruggeman’s equation, while the electrode surface coverage by the particles is modeled in terms of an area correction to the electrode kinetics. For the range of parameters analyzed, applying these two corrections enables the modeling of particle-containing thin electrolyte films covering the cathode in terms of equivalent homogenous electrolytes with modified properties. The latter can then be analyzed using simpler approaches. Particulate effects on cathode capacity at saturation and saturation length are also quantified.