Hussain Raja Rizwan, Alhozaimy Abdulrahman, Al-Negheimish Abdulaziz, Singh D D N
Center of Excellence for Concrete Research and Testing (CoE-CRT), Civil Engineering Department, College of Engineering, King Saud University, PO Box: 800, Riyadh, 11421, Saudi Arabia.
Civil Engineering Department and The Center of Excellence for Concrete Research and Testing, College of Engineering, King Saud University, Riyadh, Saudi Arabia.
Sci Rep. 2022 Jul 21;12(1):12449. doi: 10.1038/s41598-022-16654-w.
This communication reports the effect of phosphorus (P) added in micro concentration range in steel on kinetics, mechanism and growth of passive film in contact of chloride contaminated concrete. Electrochemical impedance spectroscopy, direct-current polarization, mass loss and Raman spectroscopic techniques were used to arrive at the findings. The results showed that an intentional addition of P in steel (0.064%) makes it more prone to uniform and localized corrosion (about 1.1 and 1.7 times) than the steel having low phosphorus (< 0.016%, present as tramp element) exposed under wet/dry conditions in simulated pore solution added with chloride and in the absence of this ion. A similar effect is also noted for the rebars embedded in mortars. Identification of corrosion products formed on steel rebars surface by Raman spectroscopy reveals thermodynamically stable maghemite and goethite phases on the surface of low P content steel. Unstable phase of lepidocrocite is recorded on the surface of higher phosphorus steel rebars. The findings are discussed with experimental evidence and taking clues from the published literature to arrive at plausible mechanism for this behaviour.
本通讯报道了钢中微量添加磷（P）对处于氯化物污染混凝土接触环境下的钝化膜动力学、形成机制及生长的影响。采用电化学阻抗谱、直流极化、质量损失和拉曼光谱技术得出研究结果。结果表明，在模拟孔隙溶液中添加氯化物且处于干湿条件下，有意添加磷（0.064%）的钢比低磷钢（<0.016%，作为残余元素存在）更易发生均匀腐蚀和局部腐蚀（分别约为1.1倍和1.7倍），且在无该离子时也是如此。对于埋入砂浆中的钢筋也观察到类似效果。通过拉曼光谱对钢筋表面形成的腐蚀产物进行鉴定，发现低磷含量钢表面存在热力学稳定的磁赤铁矿和针铁矿相。在高磷含量钢筋表面记录到了不稳定的纤铁矿相。结合实验证据并参考已发表文献中的线索对这些发现进行了讨论，以得出这种行为的合理机制。
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