Corrosion Response of Carbon Steel Exposed to Dynamic H2S Aqueous Solution in the Presence of Bicarbonate Ions and Natural Aeration

Corrosion of carbon steel exposed to natural aeration and aqueous solutions containing HCO3- was investigated as a function of the dissolved H2S concentration under static and dynamic conditions through electrochemical and surface characterization. The results revealed the occurrence of more pitting corrosion of carbon steel at a 10 ppm H2S concentration than at a 50 ppm H2S concentration, which was mainly associated with the formation of FeCO3 crystals (higher pH condition at 10 ppm H2S) and followed by a loss of integrity for the corrosion products due to the action of dissolved oxygen; however, defective iron sulfide scale with poor adhesion to the steel was formed once the steel surface was in contact with an aqueous solution containing 50 ppm H2S, and the loose scale was easily spalled by the action of fluid flow, which resulted in an increase in the general corrosion rate for carbon steel. Thus, this study holds promise for understanding the transformation mechanisms of corrosion types and reducing corrosion failures of transportation pipelines in the oil and gas industry.