耐蚀钢筋组织及合金元素对耐蚀性能影响的研究

发布时间：2018-06-25 16:03

本文选题：耐腐蚀钢筋 + 显微组织　；参考：《安徽工业大学》2017年硕士论文

【摘要】：近年来,随着跨海大桥、海底隧道等工程的建设以及海港、海洋工程等的快速发展,越来越多的基础设施需要在海洋环境中建设,而普通钢筋不能满足耐蚀性能的要求,耐腐蚀钢筋在这种情况下应运而生。耐腐蚀钢筋具有较好的耐蚀性和较低的成本,在海洋环境中有很好的应用前景。本文在模拟海洋环境下采用周浸实验,研究了具有不同组织和合金元素含量的钢筋的腐蚀速率随时间的变化规律;用光学显微镜、扫描电镜、XRD等方法研究了钢筋锈层及物相构成随时间的演变;采用动电位极化曲线和阻抗谱探讨了钢筋耐腐蚀的机理。结论如下:在3.5%NaCl模拟的海洋环境中,相同成分的F+B钢筋的自腐蚀电位高于F+P钢筋,前期平均腐蚀速率明显低于F+P钢筋;中期F+B钢筋平均腐蚀速率的稳定时间较F+P钢筋早,后期两种钢筋的平均腐蚀速率相近。在3.5%NaCl溶液中浸泡较长时间后的交流阻抗值相当。表明了两类不同显微组织对钢筋基体耐蚀性能的影响只停留在稳定锈层形成之前。合金元素Cr、Mn含量更高的钢筋极化曲线出现了不稳定的钝化膜,Cr、Mn的加入提升了钢筋前期的点蚀倾向,初期平均腐蚀速率明显较含Cr、Mn较低的钢筋高,长期浸泡的阻抗值明显较大,腐蚀后期的平均腐蚀速率下降明显。而单独加入Cr元素(1.26%)的钢筋在整个腐蚀周期内的平均腐蚀速率明显的较低,低于低Cr(0.04%)钢筋,高Cr元素含量的钢筋基体自腐蚀电流明显较低,且出现明显钝化现象,前期的平均腐蚀速率平缓,实验中Cr、O元素通过在裂纹和孔洞处富集形成化合物而降低基体的平均腐蚀速率,后期平均腐蚀速率有下降的趋势。腐蚀过程中没有发生Mn元素明显的富集现象,表明了在3.5%NaCl溶液环境情况下Mn元素对腐蚀速率的的影响不大。实验过程中钢筋的锈层厚度都是随着腐蚀周期的延长而逐渐加厚,锈层中主要物相由Fe3O4、γ FeOOH和α FeOOH组成,还可能在前期有少量的NaCl侵入。腐蚀后期棉絮状α FeOOH物相的生成对平均腐蚀速率的降低起重要作用,显微组织类别和合金元素含量都对锈层中物相的变化有着一定的影响,可通过人工控制显微组织类型和控制合金元素添加量的方法来改善钢筋耐蚀性能。
[Abstract]:In recent years, with the construction of cross-sea bridges, subsea tunnels and other projects, as well as the rapid development of seaports and ocean engineering, more and more infrastructure needs to be built in the marine environment, but ordinary steel bars can not meet the requirements of corrosion resistance. Corrosion resistant steel bar emerges as the times require in this case. Corrosion resistant steel bar has good corrosion resistance and low cost, and has a good application prospect in marine environment. In this paper, the variation of corrosion rate of steel bars with different microstructure and alloy element content with time was studied by means of cycle immersion experiment in simulated marine environment, and the corrosion rate of steel bars with different microstructure and alloying elements was studied by optical microscope. The evolution of rust layer and phase composition over time was studied by SEM and XRD, and the mechanism of corrosion resistance of steel bar was investigated by potentiodynamic polarization curve and impedance spectrum. The conclusions are as follows: in the marine environment simulated by 3.5 NaCl, the self-corrosion potential of the same composition FB steel bar is higher than that of the F-P steel bar, and the average corrosion rate in the early stage is obviously lower than that of the F-P steel bar. The average corrosion rate of F B steel bar is earlier than that of F P steel bar in the middle period, and the average corrosion rate of the two kinds of reinforcement is similar in the later stage. After soaking in 3.5% NaCl solution for a long time, the AC impedance is equal. The results show that the effect of two kinds of microstructure on the corrosion resistance of steel matrix only stays before the formation of stable rust layer. The polarization curve of steel bar with higher Cr-Mn content of alloy element appears unstable passivation film and Cr-Mn increase the pitting corrosion tendency of steel bar in the early stage, the average corrosion rate in the initial stage is obviously higher than that in the steel bar with lower Cr-Mn content, and the impedance value of long-term immersion is obviously higher than that of the steel bar with lower Cr-Mn content. The average corrosion rate decreased obviously in the late stage of corrosion. However, the average corrosion rate of steel bars added with Cr (1.26%) in the whole corrosion cycle is obviously lower than that of low Cr (0.04%) steel bars, and the self-corrosion current of steel bars with high Cr content is obviously lower, and the passivation phenomenon is obvious. The average corrosion rate in the early stage was gentle. In the experiment, the average corrosion rate of the matrix was decreased by the accumulation of Cr-O in the cracks and pores, and the average corrosion rate decreased in the later stage. There was no obvious enrichment of mn in the corrosion process, which indicated that mn had little effect on the corrosion rate in 3.5 NaCl solution. In the process of experiment, the thickness of the rust layer of steel bars is gradually thickened with the extension of corrosion cycle. The main phases in the rust layer are composed of Fe _ 3O _ 4, 纬 -O _ (OH) and 伪 -Fe _ (OOH), and may be invaded by a small amount of NaCl in the early stage. In the later stage of corrosion, the formation of the cotton-like 伪 -FeOOH phase plays an important role in the decrease of the average corrosion rate, and the microstructure and the content of alloying elements have a certain influence on the changes of the phase in the rust layer. The corrosion resistance of steel bars can be improved by manually controlling the microstructure type and controlling the amount of alloying elements.
【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1

【参考文献】