Spatial Interactions among Localized Corrosion Sites
Journal of the Electrochemical Society
Interactions among local pit sites were investigated using a 5 ϫ 5 array of 25 electrodes consisting of closely spaced, flushmounted 316 stainless steel wires. Three types of interactions occurred when actively corroding pits existed while the remaining electrodes were initially passive in 0.05 M NaCl solution. Suppression of pitting on nearby electrodes occurred due to ohmic potential drop near pre-existing pits. Enhancement of pitting at initially passive electrodes was observed and
... erved and attributed to both temporary alternations in the local solution composition and a more persistent effect attributed to some action of the locally altered solution composition on nearby passive surfaces. The exact origin of the damage on the nearby passive surface is unknown. Each of these effects exhibited different periods of persistency after pit deactivation. A phenomenological model was developed and used to simulate some of the features of the experimental findings. The model included stochastic pit initiation and interactions promoted by surface damage and concentration effects or inhibited by ohmic drop. The model successfully reproduced some of experimental observations and illustrated the formation of nonrandom corrosion damage patterns even on a simulated homogeneous surface. Figure 1. Schematic of the local changes that occur near a pit site. Included are changes in the local solution chemistry by diffusion, oxide film damage, and ohmic potential drop in solution.