The control of corrosion of carbon steel is a major challenge in oil and gas production environments. Thus, corrosion failures can lead to costly repairs, plant shut¬downs as well as health and environmental hazards. The presence of typical production gases, such as CO2 and H2S, can increase the corrosiveness of produced fluids and, hence, the severity of corrosion of carbon steel.1 3 Many studies have investigated the C02 H2S H20 system in order to better understand the corrosion of steel, surface films/scales and corrosion mechanisms involved. Some early research in this field has suggested that a low concentration of H2ร (80°Cj when a protective film forms.4’ In a Norwegian study,6 it was suggested that this effect of H2S could be significant only in the low pH range (pH