Pitting Corrosion of Steel Induced by Al2O3 Inclusions

To study the effect of Al2O3 inclusions on pitting corrosion in steel, our researchers utilized industrial pure iron as the raw material with the addition of a proper amount of pure aluminum powder to form Al2O3 inclusions. Corrosion experiments were performed by exposing the samples to a 6% FeCl3 solution at room temperature (25 degrees C) for different lengths of time. Microscopic corrosion morphology was observed by scanning electron microscope (SEM), and the size change of the inclusions was quantitatively analyzed with Image Pro Plus. The experimental results showed that pitting corrosion arose preferentially around the Al2O3 inclusions, and that pitting corrosion initiated at the junction of the Al2O3 inclusions. The steel matrix dissolved and micro-cracks occurred as the Al2O3 inclusions that were buried shallowly below the surface of the steel matrix promoted corrosion of the steel matrix. As corrosion progressed, the shallowly buried Al2O3 inclusions began to appear on the surface, and the small, shallow inclusions fell off and formed micro pits. Furthermore, the clustered distribution of alumina inclusions had a greater effect on pitting initiation than the alumina inclusions distributed alone.

为研究Al₂O₃夹杂物对钢点蚀的影响，我们的研究人员以工业纯铁为原料，添加适量纯铝粉以形成Al₂O₃夹杂物。通过将样品在室温（25℃）下置于6%的FeCl₃溶液中不同时长来进行腐蚀实验。利用扫描电子显微镜（SEM）观察微观腐蚀形貌，并使用Image Pro Plus对夹杂物的尺寸变化进行定量分析。实验结果表明，点蚀优先在Al₂O₃夹杂物周围产生，且点蚀在Al₂O₃夹杂物的连接处萌生。由于埋在钢基体表面下方较浅的Al₂O₃夹杂物促进了钢基体的腐蚀，钢基体发生溶解并出现微裂纹。随着腐蚀的进行，埋得较浅的Al₂O₃夹杂物开始出现在表面，小而浅的夹杂物脱落并形成微坑。此外，氧化铝夹杂物的聚集分布比单独分布的氧化铝夹杂物对点蚀萌生的影响更大。