Effect of Rare Earth Metal Alloying on Pitting Corrosion Resistance and Corrosion Layer Formation of High-Strength Oil Casing Steels

This study delves into the effects of rare earth metal (Ce) alloying on the pitting corrosion resistance and corrosion layer formation of high-strength oil casing steels. The research focuses on four key areas: the composition and statistical analysis of inclusions, in situ observation of localized corrosion behavior, characterization of corrosion pits in the later stages of immersion, and the morphology and composition analysis of the corrosion layer. The findings reveal that as Ce content increases from 0 to 300 ppm, the evolution of inclusions transitions through several stages, significantly influencing the corrosion resistance of the steel. Notably, the study identifies the optimal Ce content range of 61 to 120 ppm for enhancing corrosion resistance under acidic conditions. The research employs advanced techniques such as EBSD and XPS to provide a detailed understanding of the corrosion mechanisms and the role of different types of inclusions. The study concludes that controlling the Ce content within the identified range can effectively improve the pitting corrosion resistance and the integrity of the corrosion layer in oil casing steels, offering valuable insights for the production of high-quality oil casing materials.