Mechanistic investigation of localized electrochemical corrosion in defective regions of Cu Ni alloys under dynamic marine environment using a φ0.1 mm wire beam electrode

In this study, wire beam electrode technology, combined with electrochemical impedance spectroscopy (EIS) and surface morphology analysis, was employed to systematically investigate the localized corrosion behavior of depressed and protrusion defects on B18 Cu Ni alloy in a dynamic 3.5 wt% NaCl solution. The results demonstrate that the lowest region of the depressed defect and its upstream side exhibit intense anodic dissolution due to enhanced turbulent mass transfer and cl − enrichment, with the local corrosion intensity index reaching 0.35 within 24 h. Vortex impacts induced by fluid separation on the downstream side of convex defects lead to greater corrosion depth compared to the top region. Compared with the protrusion defect features, upstream side beneath the depressed features exhibits a higher density of localized anodic sites and larger current values. This observation confirms that samples with shallower defect depths tend to experience more pronounced radial deepening. EIS and surface roughness analyses further reveal that shear forces disrupt the dynamic evolution of the double-layer structure of corrosion product films. Collectively, these findings elucidate the local corrosion mechanisms under the synergistic influence of dynamic interference and electrochemical processes • Development of a ϕ0.1 mm wire beam electrode array enabling microscale mapping of localized corrosion in Cu Ni alloys under dynamic NaCl flow. • Identification of defect geometry effects showing that concave and convex structures drive localized anodic dissolution through shear stress and Cl − enrichment. • Revelation of dynamic corrosion-product film evolution and its control by shear-induced damage, porosity, and thickness. • Demonstration of real-time flow corrosion monitoring via multi-electrode equivalent circuit fitting to quantify local electrochemical behavior.