Corrosion Behavior of Oxide Scale of 5Cr Steel in CO2 Flooding Environment

Medium-Cr steel is considered as the most economical and effective pipeline material in a CO2 flooding environment; however, the effects of iron oxides on the corrosion resistance of medium- Cr steel are still not clear. Therefore, in the present study, a high-temperature, high-pressure reactor was used to accelerate the corrosion of a rolled oxidized sheet of 5Cr steel. The corrosion behavior of oxide scale leaching was studied by comparing the mass loss and gain rate with bare steel, through using XRD, Raman, XPS, SEM, EDS, EPMA and other methods. It was found that the 5Cr steel rolled scale was composed of three layers: the innermost layer contained Fe3O4, the middle layer consisted of Fe2O3, and the outer layer contained Fe3O4 and a small amount of Fe2O3. In the CO2 environment, the oxide scale mainly dissolved in the initial stage, and corrosion products were deposited in the later stage. The oxide scale delayed the occurrence of corrosion, and eventually, similar to the bare steel, a double-layer product film was formed. Also, the possible corrosion mechanism of the medium-Cr steel with the oxide scale was given.

Automated summary

This study investigated the corrosion behavior of rolled oxidized sheet of 5Cr steel in a high-temperature, high-pressure CO2 environment. The results showed that the oxide scale, composed of Fe3O4 and Fe2O3, delayed the occurrence of corrosion and eventually formed a double-layer product film similar to bare steel.