Influence of rare earth elements on corrosion resistance of BFe10-1-1 alloys in flowing marine water

The corrosion behavior of BFe10-1-1 alloy with different rare earth (RE) contents in simulated flowing marine water was investigated by X-ray diffractometer and scanning electron microscope (SEM). It was demonstrated that the corrosion rate of BFe10-1-1 alloy with the same chemical compositions in faster flow velocity of marine water was higher than that in a lower flow velocity of marine water. Fixing the flow velocity, BFe10-1-1 alloy had the best flushing corrosion resistance when the RE content was 0.04wt.%. The consequence of such good corrosion resistance was attributed to the formation of compact protective film on alloy surface containing RE phase such as CeNi5. The RE-contained film combines with other corrosion products firmly, which was difficult to fall off from the alloy surface in the flowing marine water. Additionally, SEM analysis confirmed that pitting mechanism, which would be transformed to spalling mechanism gradually with further increasing RE content, was the prevalent mechanism when the alloy contained 0.04wt.%RE.