含Cr低合金钢在货油舱下底板环境中的腐蚀行为

Corrosion Behaviors of Cr Low-Alloy Steel in Bottom Plate Environment of Cargo Oil Tanks

为探究货油舱下底板环境中的腐蚀机理并开发满足该服役条件的的低合金耐蚀钢,采用自制的货油舱下底板强酸性Cl-溶液模拟腐蚀装置,进行Cr含量不同的低合金钢的腐蚀行为研究.测量了模拟腐蚀实验中各合金钢的平均腐蚀速率,观察了实验后各试样表面的宏观形貌,应用SEM、EDS对腐蚀表面的微观形貌及元素分布进行了分析,并应用EBSD和TEM技术分析了钢的微观结构对该环境下腐蚀性能的影响,同时对不同Cr含量的低合金钢进行了极化曲线和交流阻抗谱分析.结果表明：货油舱下底板环境中,Cr含量为1％～3％时,腐蚀速率随着Cr含量的升高逐渐增大,点蚀现象随之变得明显;随Cr含量的增加,合金钢中的小角度低能晶界含量增加,同时钢的局部位错密度增加,两种微观结构综合作用促使腐蚀速率增大;腐蚀实验结果与电化学分析结果是对应的.

In order to reveal the corrosion mechanism of the bottom plate environment of cargo oil tanks and to develop new low-alloy steels under such environment,a home-made cargo oil tank corrosion simulation device with the strong-acid C1-solution corrosion on the bottom plate,was used to investigate the corrosion behaviors of low-alloy steels with different Cr contents.Specifically,the average corrosion rates of the steels in the corrosion test were measured with the corresponding morphology observation,and the micromorphologies and element distributions of the steels were characterized respectively by means of SEM and EDS.Moreover,the effect of the steel microstructure on the corresponding corrosion-resistance was analyzed by means of EBSD （Electron Backscattered Diffraction）and TEM,and the polarization curves and AC impedance spectroscopy of the steels with different Cr contents were tested.The results show that （1） when the Cr content increases within a range of 1％ ～ 3％ in the bottom plate environment,the corrosion rate gradually increases and the surface pitting phenomenon becomes obvious; （2） with the increase of the Cr content,the proportion of small-angle low-energy grain boundary and the dislocation density both improve,and the changes of the two microstructures both play their roles in the increase of the corrosion rate ;and （3） the corrosion test results accord well with the electrochemical analysis results.