Effect of strain rate on stress corrosion cracking of X100 pipeline steel in environments with sulfate-reducing bacteria

Abstract

Abstract Pipelines installed in the seabed for long periods suffer from high stress levels, and the sea mud environment is complex because it contains various microorganisms that make pipelines prone to stress corrosion cracking (SCC). In this study, a self-designed stress electrochemical corrosion test device was adopted to ensure the normal growth and metabolism of sulfate-reducing bacteria (SRB). The effects of strain rate on the SCC behavior of X100 pipeline steel with SRB in a simulation solution of sea mud from the South China Sea were studied using the slow strain rate test, electrochemical impedance spectroscopy, and scanning electron microscopy fractography. Results show that SRB can promote the stress corrosion susceptibility of X100 pipeline steel. As strain rate increases, the stress corrosion susceptibility decreases in general. When the strain rate is 5 × 10−7 × s−1, the stress corrosion susceptibility is largest and SCC occurs. Under the impact of SRB and strain rate, the stress corrosion fracture mechanism is hydrogen embrittlement mechanism. With the increase in strain rate, the effect of SRB becomes weak and the stress corrosion susceptibility shows a decreasing trend in general. Consequently, SCC does not occur in the specimen and the fracture is dominated by mechanical factors.