Morphology of Corrosion Pits Induced by Stray Current and Chloride in RC Transportation Infrastructure

This paper investigates the morphological characteristics of corrosion pits in reinforced concrete (RC) induced by stray current and chloride ions. The specimens retrieved from different corrosion environments were tested by X-ray computed tomography (CT). Corrosion pits were digitally reconstructed and analyzed. It was found that the morphological nonuniformity of corrosion pits is deeply related to the compactness of the concrete around the steel reinforcement. About three-quarters of the pits are flat interiors with a scalloped form, while the others are rounded interiors with an arched form. The roughness is adopted for the analysis of pitting corrosion. The increase for the width/area of the corrosion pit in specimens induced by the chloride ions is about one-third of that induced by the stray current. When the corrosion degree is similar, the corrosion pit induced by stray current is narrower than that induced by chloride ions. Stray current exacerbates the nonuniformity of pitting corrosion. The results refine the corrosion pit morphology and can be helpful for the further understanding the nonuniform distribution of the corroded steel reinforcement.