Q345D低合金钢在海洋潮差区的腐蚀规律及电化学行为研究

Electrochemical Investigation and Corrosion Behavior of Low Alloy Steel Q345D in Marine Tidal Zone

通过在青岛海域2年实海挂片暴露试验研究Q345D低合金钢和对比材料Q235B普碳钢在潮差区的腐蚀行为。试验结果表明,Q345D钢在实海潮差区1年和2年周期的平均腐蚀速率都小于Q235B钢,且两种钢锈层组成和结构基本类似,但Q345D钢表面锈层较厚,且更致密均匀。通过室内模拟海水周浸腐蚀试验研究两种钢的初期腐蚀行为,通过腐蚀数据的回归拟合分析得出,在腐蚀起始阶段,Q345D钢与Q235B钢的腐蚀倾向差别不大,但随着周浸时间的延长,腐蚀速率逐渐降低,且Q345D钢表现出比Q235B更好的耐全面腐蚀性能。宏观电化学阻抗谱和微区阻抗谱测试结果也证实,Q345D低合金钢形成的腐蚀产物膜层具有比Q235B钢更高的膜层电阻,且能够在更短时间内形成稳定的腐蚀产物膜层。

The corrosion behavior of low alloy steel Q345 D and carbon steel Q235 B in marine tidal zone is investigated by outdoor corrosion test for 2 years in Qingdao sea area located on the east coast of China. The depth losses of steels exposed for 1 year and 2 year show that the average corrosion rates of Q345 D are lower than that of the carbon steel Q235 B in marine tidal zone, and the structure observation and composition of rust layers for two kinds of steels are close. Compared with Q235 B, the corrosion products formed on Q345 D is more compact and uniform. Moreover, the early corrosion behavior of Q345 D and Q235 B is studied by laboratory cyclic-immersion corrosion test for a period of 30 days in artificial seawater, and the regression analysis is conducted to study the process of corrosion. The results show that the corrosion tendency of Q345 D is similar to that of Q235 B in the initial stage, because the electrolyte can contact the substrate directly, the corrosion rates of two kinds of steels are higher. As the time is going on, the Q345 D steel exerts a better resistance to corrosion than the carbon steel Q235 B, and the average corrosion rate is reduced obviously. In addition, the results of electrochemical impedance spectroscopic（EIS） and local electrochemical impedance spectroscopic（LEIS） indicate that the resistance of rust layer on Q345 D is higher than that on Q235 B, furthermore, a stable rust layer could form easily for the Q345 D in artificial seawater.