三种桥梁耐候钢在模拟海洋大气环境中的耐蚀性能比较

Comparative study of corrosion resistance of three weathering steels for bridges in simulated marine atmospheric environment

通过室内周期浸润加速腐蚀实验,结合腐蚀形貌观察、物相分析及电化学测试,对三种耐候桥梁钢Q355NHD、Q450NQR1、Q460q在模拟海洋大气环境(3.5%NaCl溶液)下的腐蚀行为进行对比研究。结果表明,三种耐候钢在实验周期内,腐蚀速率均呈先增大后减小的趋势。腐蚀前期,耐蚀性差异主要是由显微组织决定的,以铁素体和珠光体复相组织为主的Q355NHD、Q450NQR1钢腐蚀速率高于以粒状贝氏体为主的Q460q钢。腐蚀后期,微量合金元素在锈层中富集使其致密化,显著提高了三种钢的耐蚀性能。其中Q460q钢锈层最为致密,锈层保护因子α/γ*和电化学阻抗值|Z|最大,在该环境下表现出了最佳的耐蚀性能。

Through indoor accelerated cycling immersion test,the corrosion behaviour of three weathering steels for bridge,i.e.Q355NHD,Q450NQR1 and Q460q,in the simulated marine atmospheric environment(3.5%NaCl solution)was investigated comparatively by means of corrosion morphology observation,phase analysis and electrochemical test.The results show that the corrosion rate of three weathering steels increases firstly and then dicreases with the proceeding of the immersion test.In the early stage of corrosion,the difference in corrosion resistance is mainly determined by the microstructure.The corrosion rate of Q355NHD and Q450NQR1 weathering steels with ferrite-pearlite dual phase structure is higher than that of Q460q steel with granular bainite.In the later stage of corrosion,the micro-alloying elements are enriched in the rust layer,which enhances the densification degree and therefore improves the corrosion resistance of three steels significantly.Among them,the Q460q steel shows the best corrosion resistance in the simulated marine atmospheric environment due to the most dense rust layer,the largest protective coefficientα/γ*value as well as the highest electrochemical impedance value|Z|.