Corrosion mechanism in produced water from the petroleum industry experimental corroboration of Galvele’s Pitting Theory

Abstract

Pitting corrosion is one of the most critical degradation mechanisms affecting carbon steel pipelines exposed to CO₂-containing produced water in the petroleum industry. In such environments, high salinity, elevated chloride levels, alkaline earth cations, and restricted mass transport promote localized electrochemical conditions that may lead to severe internal corrosion. This work experimentally examines Galvele’s [1] localized acidification theory through potentiodynamic polarization tests conducted in controlled CO₂-saturated aqueous solutions containing Cl⁻, Ca²⁺, and carbonate species. Cyclic polarization curves were used to identify pitting and repassivation behavior under different chemical conditions, while surface observations correlated electrochemical responses with damage morphology. The results demonstrate that pitting susceptibility is strongly governed by chloride concentration and by the nature of the accompanying cation. Calcium supplied as CaCO₃ markedly inhibits pitting through the combined effect of carbonate ions, which neutralize localized acidity, and the rapid formation of protective carbonate-based substrates. In contrast, when calcium is introduced as CaCl₂, localized corrosion persists due to the dominant aggressive effect of chloride ions. These findings provide experimental support for Galvele’s framework and clarify the mechanistic role of calcium and carbonate species in controlling pitting corrosion in produced-water environments.