Effect of CO(2) Partial Pressure on the Corrosion Behavior of J55 Carbon Steel in 30% Crude Oil/Brine Mixture

The influence of CO(2) partial pressure on the corrosion properties, including corrosion rate, morphology, chemical composition, and corrosion depth, of J55 carbon steel in 30% crude oil/brine at 65 °C was investigated. A corrosion mechanism was then proposed based on the understanding of the formation of localized corrosion. Results showed that localized corrosion occurred in 30% crude oil/brine with CO(2). The corrosion rate sharply increased as the CO(2) partial pressure (P [Formula: see text]) was increased from 0 to 1.5 MPa, decreased from P [Formula: see text] = 1.5 MPa to P [Formula: see text] = 5.0 MPa, increased again at P [Formula: see text] = 5.0 MPa, and then reached a constant value after P [Formula: see text] = 9.0 MPa. The system pH initially decreased, rapidly increased, and then stabilized as CO(2) partial pressure was increased. In the initial period, the surface of J55 carbon steel in the CO(2)/30% crude oil/brine mixtures showed intense corrosion. In conclusion, CO(2) partial pressure affects the protection performance of FeCO(3) by changing the formation of corrosion scale and further affecting the corrosion rate.