Effect of erosion on corrosion of API X120 steel in relation to erodent particle size

Abstract

The nature of the solid erodent particles present in corrosive petroleum fluid can cause transporting pipeline to experience severe erosion and corrosion damages. The effect of erosion on corrosion behavior of API X120 steel was investigated using aluminum oxide and silicon carbide particles with different sizes as erodent and 3.5 wt.% NaCl aqueous solution saturated with carbon dioxide as a corrosive medium. The effect of the erodent particle size on the corrosion behavior of the steel material at different particle speeds and impact angles was investigated using weight loss, potentiodynamic polarization and surface analysis techniques. The erosion results confirmed that the material damage increased with increasing particle speed. It was observed that in carbon dioxide-saturated saline solution, deposition of protective iron carbonate film occurred on the steel surface. It was found that the corrosion film can provide better protection at lower particle speed than at higher speed. The ratio of total erosion–corrosion (S)/effect of erosion on corrosion (T) analysis confirmed that at higher S/T ratio, the particle speed and material removal rate are low and vice versa at lower S/T ratio. Lower S/T values for the combined erosion and corrosion tests performed with erodent silicon carbide particle compared to erodent aluminum oxide particle showed that erosion enhancement of corrosion is more evident in the test performed using aluminum oxide particle than using silicon carbide particle. The result also suggests that when subjected to larger size erodent particle, the damage to pipeline due to effect of erosion on corrosion process can be more significant compared to smaller size erodent particle.