In-line inspection via magnetic flux leakage (MFL) of a crude oil pipeline, undertaken 12 years postcommissioning, detected pitting corrosion on the upward-inclined section traversing a river gully. Field excavation subsequently localized the severe corrosion zone exclusively to the bottom of the lower portion of this inclined segment. In view of the minimal free-water fraction in the crude oil, we probe the corrosion mechanisms induced by micro-droplet deposition, identify the key parametric conditions responsible for corrosive attack, and present a predictive assessment of the resultant corrosion severity. Our investigation combines optical and electron microscopy (SEM-EDS) for microstructural and compositional profiling of the corroded steel, high-speed imaging for droplet-size characterization in the oil, and CFD-based multiphase flow simulation to correlate two-phase distribution with predicted corrosion severity. Chemical and microscopic analyses identified sparingly dispersed water droplets- bearing corrosive HCl-within the crude oil. Numerical flow simulations show that in the upward-inclined section, centrifugal forces drive these droplets wall ward, causing impingement. Post-collision, the droplets form fleeting liquid films that are quickly expelled from the surface by the antagonistic effects of surface tension and wall reaction forces. Pitting originates from the stochastic, high-frequency bombardment of discrete droplets onto confined wall regions. Each transient impact exerts a coupled mechanical-chemical effect, which collectively underpins the observed localized corrosion. The hybrid model presented herein reproduces the field-observed corrosion morphology and metal-loss magnitudes with high fidelity. Forward simulations project that the maximum localized penetration will reach 350 μm by the planned pipeline overhaul, defining a critical service-life constraint.
