Studies on corrosion inhibition of steel reinforcement by phosphate and nitrite
Studies on corrosion inhibition of steel reinforcement by phosphate and nitrite
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DOI：
10.1007/bf02480830
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发表时间：
2003-08
影响因子：
3.8
通讯作者：
L. Dhouibi;E. Triki;M. Salta;P. Rodrigues;A. Raharinaivo
中科院分区：
文献类型：
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作者：
L. Dhouibi;E. Triki;M. Salta;P. Rodrigues;A. Raharinaivo
本研究探讨了磷酸钠和亚硝酸盐作为混凝土钢筋中钢筋腐蚀抑制剂的有效性。首先，用几种碱性溶液模拟混凝土孔隙水。然后，在新拌混凝土中加入抑制剂的钢筋混凝土试件浸入氯化物溶液中。通过电化学技术，即电化学阻抗谱（EIS）、极化曲线（PC）和开路电位（OCP）测量，评估了抑制剂的有效性。采用扫描电镜（SEM）、x射线衍射（XRD）和红外光谱（FT-IR）分析了最终的混凝土状态。在模拟氯化物污染混凝土的溶液中，采用（PC）和（EIS）评价了缓蚀剂对钢筋腐蚀的影响。结果表明，当磷酸盐含量与氯化物浓度相等时，磷酸盐能抑制点蚀，而亚硝酸盐只有助于提高点蚀电位值。两种缓蚀剂在不同含量下的腐蚀速率都有所降低。采用EIS法对钢筋混凝土试样在氯溶液中的浸泡状态进行了评价。结果表明，两种缓蚀剂浸泡1年后，腐蚀速率下降。然后，浸泡3年后，没有观察到抑制剂对腐蚀速率的影响。然而，当抑制剂存在时，观察到混凝土电阻显着增加。目视检查表明，所有的钢筋在氯化物的存在下都被腐蚀了。对混凝土浸泡3年后的分析试验结果表明，就混凝土的最终状态而言，所测试的抑制剂并没有改变混凝土中化合物的类型。但最终游离氯化物含量仍高于临界氯化物阈值。傅里叶变换红外光谱（FT-IR）分析结果表明，混凝土在氯化物溶液中浸出亚硝酸盐，磷酸盐干扰了混凝土中CO32−和HCO3−的平衡。本研究的主要结论是：所测试的抑制剂在氯溶液中浸泡两年后，其效率随时间而降低。
This work deals with the effectiveness of sodium phosphates and nitrites used as inhibitors against steel corrosion in concrete reinforcement. First, concrete pore water was simulated with several alkaline solutions. Then, reinforced concrete specimens with inhibitors added in fresh concrete mix are immersed in chloride solution. The effectiveness of inhibitors was assessed by applying electrochemical techniques, namely Electrochemical Impedance Spectroscopy (EIS), Polarisation Curves (PC), and Open Circuit Potential (OCP) measurements. The final concrete condition was analysed with Scanning Electronic Microscopy (SEM), X-Ray Diffraction (XRD) and Infrared Spectroscopy (FT-IR).In solutions simulating concrete contaminated with chloride, the influence of the inhibitors on the steel corrosion was assessed by (PC) and (EIS). The results obtained show that phosphate prevents pitting corrosion when its content is equal to chloride concentration, and that nitrite only contributes to increase the value of pitting potential. Corrosion rate is reduced with both inhibitors at the different contents tested.For reinforced concrete specimens immersed in chloride solution, their conditions were assessed by applying EIS. The results indicate that after 1 year of immersion with the two inhibitors the corrosion rate decreased. Then, after 3 years of immersion no influence of inhibitors on the corrosion rate was observed. However a significant increase in concrete electrical resistance was observed when inhibitors were present. Visual examinations showed that all steel bars were corroded in the presence of chlorides.Results from analytical tests done on the concrete after 3 years of immersion show that as far as the final concrete condition is concerned, the tested inhibitors did not change the type of compounds in concrete. But the final free chloride content remained higher than the critical chloride threshold. The results of FT-IR technique showed that nitrites are likely washed out of concrete during immersion in chloride solution and phosphates interfere with the equilibrium between CO32−and HCO3−in concrete.The main conclusion of this study is: the efficiency of the tested inhibitors decreases with time, after two years of immersion in chloride solution.