Electrochemical Model of Sour Corrosion of Mild Steel: Validation at High H2S Partial Pressures

Abstract

Hydrogen sulfide (H2S) corrosion of mild steel is a serious concern in the oil and gas industry. However, H2S corrosion mechanisms, specifically at high partial pressures of H2S, have not been extensively studied; this is primarily a result of experimental difficulties and associated safety issues. The study reported herein was conducted under well-controlled conditions at H2S partial pressure of 0.096 MPa, pH values of 3.0 and 4.0, 30°C, and with rotating cylinder speed of 1,000 rpm. Short-term exposures lasting between 1.0 h and 1.5 h were used to avoid formation of any protective iron sulfide layers. The experimental results were compared with a recent mechanistic model of sour corrosion developed by Zheng, et al. (2014). The validity of the model at higher partial pressures of H2S was challenged as it was uncertain if the mechanisms identified at lower partial pressures of H2S were still valid. The comparison with the experimental results obtained in the present study indicated a good agreement betwee...