Study of the mechanism of corrosion initiation and development in the elbow of a desulfurization unit

An upright 90° elbow used in a desulfurization unit has leaked many times in a short time, leading to frequent unplanned shutdowns of the unit. It was forced to apply additional steel plates to avoid leakage. The upper wall of the failed elbow was severely corroded, and several regular corrosion holes were found around the leaking region. To reveal the root cause of the failure and explore the initiation and development mechanism of corrosion, the elbow was investigated and analyzed by macroscopic analysis, three-dimensional topography analysis, corrosion product analysis and computational fluid dynamic (CFD) simulation. Results showed that the synergy of electrochemical corrosion and fluid erosion was the main cause of elbow failure. In addition, the elbow was divided into three different sections according to the differences in corrosion characteristics, and the initiation and development mechanism of corrosion in all sections were explained in detail. Finally, countermeasures were proposed to alleviate the corrosion of the elbow.