Zn-5%Al镀层钢筋在混凝土中电化学腐蚀行为的研究

发布时间：2018-11-28 21:08

【摘要】：钢筋混凝土结构是自20世纪以来使用的最为广泛的建筑材料之一,钢筋在混凝土中的耐蚀性是研究人员长期关注的热点。混凝土中钢筋的腐蚀主要有两个原因,混凝土的碳化和氯离子的侵蚀。本文以热浸镀Zn-5%Al合金镀层作为钢筋的保护涂层,对其在混凝土中的电化学腐蚀行为做了研究,并通过将热浸镀Zn-5%Al层在混凝土模拟孔隙液和混凝土中的电化学行为对比,系统地研究了其作为混凝土中钢筋保护层的可行性。实验首先采用Tafel极化测试和电化学阻抗谱方法,研究了热浸镀Zn-5%Al镀层在混凝土模拟孔隙液中浸泡不同时间的腐蚀行为,探讨了腐蚀产物保护层试样在混凝土模拟孔隙液中的耐氯离子腐蚀性。研究表明,Zn-5%Al镀层浸泡15d后自腐蚀电流密度为1.16×10-7A/cm2,接近钢筋混凝土钝化临界值1.00×10-7A/cm2,耐蚀性最佳,对腐蚀产物进行SEM形貌分析和EDS成分分析表明此时试样表面是由片状的锌酸钙(Ca HZn)和团絮状的铝酸钙(Ca HAl)组成;腐蚀产物保护层试样在0.1mol/L的氯离子混凝土模拟孔隙液中浸泡30d后,自腐蚀电流密度为4.53×10-7A/cm2,耐蚀性优异,在1mol/L的氯离子混凝土模拟孔隙液中浸泡30d后,自腐蚀电流密度为3.37×10-6A/cm2,耐蚀性不佳,腐蚀产物保护层试样对基体的保护作用随着氯离子浓度的升高而降低,腐蚀产物保护层试样的氯离子阈值为0.2mol/L。通过干湿循环加速实验和恒电流加速腐蚀实验,使用电化学阻抗谱方法,研究了热浸镀Zn-5%Al钢筋混凝土的电化学腐蚀行为。在干湿循环加速实验中,混凝土的电阻随着浸泡时间的延长先变小,然后基本保持不变,腐蚀产物层的电阻随着浸泡时间的延长逐渐减小,普通钢筋和热浸镀Zn-5%Al钢筋表面的电荷迁移电阻随着浸泡时间的延长均逐渐减小,热浸镀Zn-5%Al钢筋的耐蚀性整体上仍然优于普通钢筋;在恒电流加速腐蚀试验中,混凝土的电阻随着浸泡时间的延长先增加然后基本保持不变,热浸镀Zn-5%Al钢筋表面腐蚀产物层的电阻及钢筋表面电荷迁移电阻随着加速时间的延长先减小,然后基本保持不变;通过恒电流加速腐蚀实验来研究热浸镀Zn-5%Al钢筋混凝土的耐蚀性与钢筋在混凝土中的自然腐蚀有较大的差距,通过干湿循环实验来研究热浸镀Zn-5%Al钢筋混凝土的耐蚀与实际更相符,更有参考价值。总体上,热浸镀Zn-5%Al镀层作为钢筋的保护层能显著提高普通钢筋在混凝土中的耐蚀性,但不如热镀锌钢筋。
[Abstract]:Reinforced concrete structure is one of the most widely used building materials since the 20th century. There are two main reasons for the corrosion of steel bars in concrete, carbonation and chloride ion corrosion. In this paper, the electrochemical corrosion behavior of Zn-5%Al alloy coating in concrete was studied. By comparing the electrochemical behavior of hot-dip Zn-5%Al coating in concrete simulated pore fluid and concrete, the feasibility of using Zn-5%Al coating as the protective layer of steel bar in concrete is systematically studied. The corrosion behavior of hot-dip Zn-5%Al coating immersed in concrete simulated pore solution for different time was studied by Tafel polarization test and electrochemical impedance spectroscopy (EIS). The corrosion resistance of protective layer samples of corrosion products in simulated pore fluid of concrete is discussed. The results show that the corrosion current density of Zn-5%Al coating is 1.16 脳 10 ~ (-7) A / cm ~ (2), close to the critical passivation value of reinforced concrete, 1.00 脳 10 ~ (-7) A / cm ~ (2), and the corrosion resistance is the best. The results of SEM and EDS analysis show that the sample surface is composed of flake calcium zincate (Ca HZn) and flocculent calcium aluminate (Ca HAl). The corrosion product protective layer samples were immersed in the chloride ion concrete simulated pore fluid of 0.1mol/L for 30 days, the corrosion current density was 4.53 脳 10 ~ (-7) A / cm ~ (2), and the corrosion resistance was excellent. The sample was soaked in the chloride ion concrete simulated pore fluid of 1mol/L for 30 days. The self-corrosion current density is 3.37 脳 10 ~ (-6) A / cm ~ (2) and the corrosion resistance is poor. The protective effect of the corrosion product protective layer on the substrate decreases with the increase of chloride ion concentration, and the chloride ion threshold of the corrosion product protection layer sample is 0.2 mol / L. The electrochemical corrosion behavior of hot-dip Zn-5%Al reinforced concrete was studied by means of accelerated dry and wet cycle test and constant current accelerated corrosion test. The electrochemical impedance spectroscopy (EIS) method was used to study the electrochemical corrosion behavior of hot-dip Zn-5%Al reinforced concrete. In the accelerated test of wet and dry cycle, the resistance of concrete decreases with the time of soaking, and then remains unchanged, and the resistance of the corrosion product layer decreases gradually with the prolongation of soaking time. The charge transfer resistance on the surface of ordinary steel bar and hot-dip Zn-5%Al steel bar decreases gradually with the prolongation of soaking time, and the corrosion resistance of hot-dip Zn-5%Al steel bar is still better than that of ordinary steel bar as a whole. In the constant current accelerated corrosion test, the resistance of concrete increases first with the prolongation of immersion time and then remains basically unchanged. The resistance of corrosion product layer and charge transfer resistance of hot-dip Zn-5%Al steel first decrease with the increase of acceleration time, and then remain unchanged. The corrosion resistance of hot-dip Zn-5%Al reinforced concrete is studied by constant current accelerated corrosion test, which is different from the natural corrosion of steel bar in concrete. The study on corrosion resistance of hot-dip Zn-5%Al reinforced concrete by dry and wet cycle experiment is more consistent with the practice and has more reference value. As a whole, hot-dip Zn-5%Al coating as the protective layer of steel bar can significantly improve the corrosion resistance of ordinary steel bar in concrete, but it is not as good as hot-dip galvanized steel bar.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

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