Effects of yttrium on corrosion behavior of 09CrCuSb alloy in high concentration sulfuric acid

SEM and XRD analyses and electrochemistry tests were conducted to investigate the effect of rare earth yttrium on the corrosion behavior of 09CrCuSb alloy. The mass loss of the sample with yttrium addition in 85% sulfuric acid solution at 110°C after 72 hours was much lower than that of the sample without yttrium addition at the same condition. The results indicate that yttrium improves the corrosion resistance of 09CrCuSb alloy effectively. Investigating the structure of the corrosion scale, it is found that yttrium addition facilitates formation of a fine, uniform and compact corrosion layer. Moreover, yttrium addition strengthens the contact between corrosion layer and matrix to improve the scale adherence intensity. As a result, the self-corrosion current is reduced, and the polarization resistance is heightened to enhance the resistance against electrochemical reaction, thus the alloy rapidly tends to passivation with lower passive current density.