Influence of chromium of low content on the corrosion behavior of SA106B carbon steels in high-temperature pressurized LiOH medium

•A content of 0.36 wt% Cr could play an obvious role in resisting corrosion.•The oxide films were both typical double-layered oxide structures.•Chromium oxide exists in the inner oxide layer of SA106B with 0.36 wt% Cr.•No chromium oxide was detected in the thick oxide layer of SA106B with 0.02 wt% Cr. The corrosion of carbon steel (CS) pipelines widely troubles the primary circuit system of pressurized heavy water reactors. The element chromium (Cr) plays a crucial role in resisting corrosion. However, the mechanism of oxide film formation and dissolution on low Cr-content CS remains unclear. A comparison study in corrosion behavior between SA106B with 0.02 wt% and 0.36 wt% Cr was carried out with weight loss tests, electrochemical measurements, and morphology observations. Immersion tests were performed in deaerated lithium hydroxide solution at 553 K and 6.3 MPa for 30 days. The results showed that although the content of Cr was as low as 0.36 wt%, it exhibited relatively high corrosion resistance to the SA106B with 0.02 wt% Cr. Two layers of oxide film were formed on both the two CSs and chromium oxide was present in the inner oxide layer of 0.36Cr CS. The possible formation mechanism of oxidation film with low content of Cr in high-temperature water was discussed.