苯并三唑对水泥砂浆中钢筋的阻锈作用

Effect of Benzotriazole as Corrosion Inhibitor for Reinforcing Steel in Cement Mortar

应用腐蚀电位(Ecorr)、极化电阻(Rp)和砂浆保护层电阻率(ρc)研究了苯并三唑(BTA)对钢筋电极腐蚀电化学行为的影响.通过电化学阻抗谱(EIS)、循环极化(CP)和循环伏安(CV)结果对比了BTA与NaNO2(SN)对钢筋电极在未处理、预锈蚀和内掺氯盐3种状态下3.5%(w)氯盐浸泡360d后的阻锈效率.利用环境扫描电镜(ESEM)与能谱分析(EDS)解释了BTA对水泥基材料中钢筋的阻锈机理.结果表明:3种状态下BTA均能明显降低砂浆中钢筋的均匀腐蚀速率,且其阻锈效率高于SN.在未处理与预锈状态下,BTA抑制点蚀的能力稍弱于SN;但在内掺氯盐的状态下,BTA表现出了较大的点蚀阻力.BTA除了能在钢筋表面形成复杂的保护膜,从而有效抑制氯盐的破钝化作用.ESEM/EDS结果表明BTA还能与砂浆基体形成较多富钙C-S-H凝胶,可能优化了钢筋/砂浆界面区的孔结构,形成更致密的微观结构,显著延缓了氯盐向钢筋表面的传输进程,较好地保护了钢筋.适量的BTA对砂浆360d的基本力学性能无明显影响.

The effects of benzotriazole （BTA） on the corrosion behavior of reinforcing steel in mortar specimens were studied by corrosion potential （Ecorr）, polarization resistance （Rp）, and resistivity of mortar cover （ρc）. Additionally, the corrosion inhibiting efficiencies of BTA and NaNO2 （SN） were compared after exposure to 3.5% （w） NaCl solution for 360 d. Three samples with different surface conditions （as-received reinforcing steel, pre-rusted reinforcing steel, and chloride-admixed in mortar） were studied using electrochemical impendence spectroscopy （EIS）, cyclic polarization （CP） and cyclic voltammetry （CV）. Environmental scanning electron microscopy （ESEM） and energy dispersive spectroscopy （EDS） were employed to obtain the mechanism of the inhibiting efficiency of BTA in cementitious materials. The results show that under all three conditions, BTA strongly reduces the uniform corrosion rates of reinforcing steels in mortar with inhibiting efficiencies better than those of SN. On the other hand, the pitting corrosion resistance of specimen with BTA is slightly lower than that with SN for the as-received and pre-rusted reinforcing steels. However, when chlorides were pre-mixed in mortar, BTA showed better protection against pitting corrosion. In previous investigations, BTA was found to form a complex film on the surface of the reinforcing steel which restrained the depassivation of the passive film by Cl-. The results of ESEM/EDS indicate that BTA facilitates more Ca-rich C-S-H gel in the mortar matrix, which may refine the microstructure of the reinforcing steel/mortar interface. The compact microstructure delays the transport of Cl- towards the steel surface, which protects the reinforcing steel effectively. The long-term （360 d） strength of the mortar specimen is not affected obviously when BTA is used in appropriate proportions.