轨道交通隧道内预埋槽道的耐腐蚀性能研究

Study on Corrosion Resistance of Pre-Buried Channels in Rail Transit Tunnels

为了深入了解预埋槽道不同防腐蚀涂层体系的耐腐蚀性能差异,收集了某批地铁项目的 4组槽道样品。借助2 400 h中性盐雾试验结果并通过扫描电子显微镜(SEM)、能谱分析仪(EDS)、金相显微镜、电化学阻抗谱(EIS)、耐砂浆性试验等对试验的预埋槽道的耐腐蚀性能进行了分析与表征。结果表明:4组防腐蚀样品都含有热镀/锌层,中性盐雾试验后1号样品(锌层+中间层+有机涂层)和2号样品(锌层+有机涂层)表面无明显变化,3号样品(锌层+有机涂层)锚杆连接处和端部出现严重鼓泡但无红锈,4号样品(单一热镀锌层)表面被红锈覆盖;SEM/EDS结果表明存在有机涂层的防腐蚀体系腐蚀过程主要由氧扩散效应控制,含锌铝的中间层防腐蚀效果明显,腐蚀产物主要是锌和铝的氧化物。2 400 h中性盐雾试验的电化学阻抗谱的测试结果表明:1号样品低频阻抗值降低到105Ω·cm2,有机涂层基本失效,2号样品低频阻抗值降低到106Ω·cm2,有机涂层仍有效,3号样品低频阻抗值降低到104Ω·cm2,有机涂层基本失效,4号样品防腐蚀性能效果有限;耐砂浆性试验结果表明:1,2,3号(存在有机涂层)样品表面无明显变化,4号(仅单一热镀锌层)样品表面有轻微腐蚀现象。预埋槽道防腐蚀体系的防腐蚀材料及制备工艺是决定耐腐蚀性能强弱的关键因素。

In order to understand the difference of corrosion resistance of different anticorrosive coating systems for embedded channel,four groups of channel samples were collected from a batch of subway projects.From the results of neutral salt spray tests for 2400 h and through the means including scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),metallographic microscope,electrochemical impedance spectroscopy(EIS)and mortar resistance test,the corrosion resistance of pre-buried embedded channels was analyzed and characterized.Results showed that all the four groups of anticorrosive samples contained hot-dip galvanizing layer.After neutral salt spray test,the surface of Sample 1(zinc layer+intermediate layer+organic coating)and Sample 2(zinc layer+organic coating)presented no obvious change.The bolt joints and ends of Sample 3(zinc layer+organic coating)appeared serious bubbling but no red rust occurred.The surface of Sample 4(single hot-dip galvanizing coating)was covered with red rust.Moreover,SEM/EDS results showed that the corrosion process of organic coating was mainly controlled by oxygen diffusion effect,and the corrosion products of zinc-aluminium interlayer were mainly composed of oxides of zinc and aluminium.The results of electrochemical impedance spectroscopy after 2400 h salt spray test exhibited that the low frequency impedance value of Sample 1 decreased to 105Ω·cm2,and the organic coating basically failed;the low frequency impedance value of Sample 2 decreased to 106Ω·cm2,and the organic coating was still effective;the low frequency impedance value of Sample 3 decreased to 104Ω·cm2,and the organic coating basically failed;Sample 4 had some limited anti-corrosion effect.The results of mortar resistance test indicated that there was no obvious change in the surface of organic coating Sample 1,2,3,while slight corrosion phenomenon was observed on the surface of Sample 4.Therefore,the anti-corrosive material and preparation technology of the anticorrosive system were the key factors to determine the anticorrosive performance of pre-embedded channels.