Flow Loop Study of NaCl Concentration Effect on Erosion, Corrosion, and Erosion-Corrosion of Carbon Steel in CO2-Saturated Systems

Erosion-corrosion deterioration of carbon steel in carbon dioxide (CO2)-saturated systems with sand is a problem in the oil and gas industry because the combined effects of erosion and corrosion can reduce the protection provided by iron-carbonate scale formation or inhibitors. Oil and gas production can be accompanied by the formation water (typically chloride containing brine). Some effects of chloride concentration on corrosion are not widely known, and this can result in misleading conclusions. The goal of this paper was to contribute to a better understanding of the effects of chloride concentration in CO2 corrosion. Previous studies reported in the literature and experimental and theoretical studies conducted in the present work have shown that increasing the sodium chloride (NaCl) concentration in solution has three important effects on corrosion results. First, standard pH meter readings in high NaCl concentration solutions require corrections. Second, increasing the NaCl concentration decreases the CO2 concentration in solution and therefore contributes to a decrease in the corrosion rate. Third, increasing the NaCl concentration increases the solubility of FeCO3 and therefore reduces the likelihood of forming an iron carbonate scale. High NaCl concentration also decreases the sand erosion rate of the metal slightly by increasing the density and viscosity of the liquid.