碳钢中夹杂物诱发点蚀的规律和特性研究

海洋环境对于金属的腐蚀具有明显的加速作用，尤其在高铁海底隧道环境中，金属比正常的服役时间变短，这种腐蚀情况下会影响高铁的安全和准点运行。基于以上背景，通过夹杂物自动扫描、钢的加速腐蚀及电化学测试对钢中的夹杂物诱发腐蚀行为进行系统分析，重点分析了高铁轨旁信号设备连接金属件（Q235）中夹杂物在盐雾环境下的腐蚀行为。结果表明：钢中主要夹杂物为氧化物、硫化物或者其复合夹杂，而这两类夹杂物对于诱发钢基体点蚀的原因不同。其中数量最多、尺寸小于5 μm类型的夹杂物为硫化物夹杂和氧硫复合类型夹杂物；数量少、尺寸大于5 μm的夹杂物为氧化物夹杂。在服役过程中，钢中硫化物夹杂易溶解脱落形成点蚀坑，而氧化物夹杂周围基体会先溶解引起夹杂物脱落形成点蚀坑，复合类夹杂物也是诱发钢发生腐蚀的因素，不同复合类型的夹杂物腐蚀方式不同，硫化物夹杂和氧硫复合夹杂对碳钢影响较大。电化学测试表明自腐蚀电位约为为−0.1 V，Q235钢本身抗腐蚀能力不强。夹杂物在腐蚀过程中参与了腐蚀，引起阳极极化曲线的波动，加快了Q235钢的腐蚀情况。研究结果对于认识和改善钢的耐腐蚀性能有指导意义。

Law and feature of pitting caused by inclusion in carbon steel

The marine environment significantly accelerates metal corrosion especially in underwater or undersea tunnels for high-speed rails, where the life of the metals will be shorter than normal life time; moreover, this type of corrosion critically affects the safety, promptness, and efficient operation of high-speed rails. Accordingly, this article systematically analyzes the behavior of inclusion-induced corrosion on steel by automatic scanning of inclusions, accelerated corrosion tests, and electrochemical testing. It focuses on the analysis of inclusions in steel used for high-rail signal connection equipment (Q235) and corrosive behavior in foggy environments. The results show that the types of inclusions in steel are oxides, sulfides, and composite inclusions, and each type of inclusion has different effects on pitting corrosion of the steel structure. Among the inclusions, the main types largely present are sulfide inclusions and oxygen-sulfur composite inclusions, which have a particle size smaller than 5 μm. The inclusions larger than 5 μm are oxide inclusions and they are present in small number. When components or steel structures are used in marine environment, sulfide inclusions in steel are easily dissolved and deformed to form pits, while oxide inclusions around the substrate get dissolved and fall off resulting in pitting corrosion. Composite inclusions also induce steel corrosion. Therefore, different types of inclusions induce corrosion in different ways. Sulfide inclusions and oxygen-sulfur composite inclusions have a greater impact on carbon steel. Electrochemical tests show that the self-corrosion potential is approximately −0.1 V, and Q235 steel itself is not resistant to corrosion. As inclusions participate in corrosion process, they cause fluctuations in the anodic polarization curve and accelerate the corrosion of Q235 steel. The research results are of great significance for understanding and improving the corrosion resistance of steel, corrosion resistance of metal equipment in the undersea tunnel environment, and improving the safety and efficiency of high-speed railways.