Mechanistic modeling of pitting corrosion in thin film microelectrodes

​Thin film microelectrodes operating under sustained electrical bias in chloride containing environments are susceptible to localized corrosion that can compromise long term reliability. This study presents a combined experimental and computational investigation of pitting corrosion in thin film microelectrodes using electrochemical polarization measurements and peridynamic based modeling. Potentiostatic and Tafel polarization experiments were performed on gold, platinum, titanium tungsten, and iridium oxide microelectrodes in phosphate buffered saline at 37 °C, revealing material dependent anodic behavior. Gold was selected for detailed modeling due to its well-defined activation-controlled polarization response, enabling quantitative linkage between measured current density and material loss. A peridynamic framework was developed to model corrosion driven moving boundaries and directly couple polarization derived current densities to localized material dissolution. 1D simulations captured uniform dissolution behavior and established baseline corrosion rates, while 2D simulations explicitly incorporated localized pit formation and pit spacing effects. Extension of the 2D results to 3D representations enabled quantitative prediction of pit density, mass loss, and pit induced delamination without remeshing or prescribed interface tracking. Electrical resistance measurements under constant bias exhibited channel specific behavior that was explained by competing effects of pit growth and interfacial undercutting that increase conductive area, and partial oxidation or thinning that reduces electrical conduction.