A517Gr.Q海工钢在模拟海洋飞溅区的腐蚀行为研究

Corrosion Behavior of A517Gr.Q Marine Steel in Simulated Corrosive Condition of Marine Splashing Zone

利用失重法和SEM、EDS、XRD、FT-IR等分析技术研究了A517Gr.Q海工钢在模拟海洋飞溅区干湿交替环境下的腐蚀行为以及环境湿度的影响。结果表明:在飞溅区干湿交替环境下,A517钢的腐蚀较为严重,在敞口和半封闭两种模拟环境(实验箱平均环境湿度分别为(62±5)%、(83±5)%)下腐蚀失重均随着时间的延长而增大,平均腐蚀速度都是先增大后趋于平稳。腐蚀产物均是由γ-Fe_(3)O_(4)OH、β-Fe_(3)O_(4)OH、α-Fe_(3)O_(4)OH和Fe_(3)O_(4)组成。在62%RH环境下电解液膜的停留时间短,干/湿状态变化程度更加彻底,样品表面生成了更多的腐蚀产物,同时生成了较多具有高阴极氧化活性的β-Fe_(3)O_(4)OH,锈层疏松多孔,表现为不均匀的全面腐蚀,材料的腐蚀程度较为严重。而在83%RH环境下,产物膜中生成了更多致密均匀的Fe_(3)O_(4),对侵蚀性Cl-具有一定的阻挡作用。

The corrosion behavior of A517Gr.Q steel was studied by mass loss method,SEM,EDS,XRD,and FT-IR in a cyclic wet/dry testing chamber,which was specially designed to simulate the corrosion condition of marine splash zone i.e.cyclically wetting in 3.5%NaCl solution and drying in atmospheres with humidity of either(62±5)%or(83±5)%.The results show that A517 steel is suffered from serious corrosion in the simulated environments of marine splash zone.The corrosion mass loss increases with time,while the average corrosion rate increases first and then stabilizes.The corrosion products are all composed ofγ-Fe_(3)O_(4)OH,β-Fe_(3)O_(4)OH,α-Fe_(3)O_(4)OH and Fe_(3)O_(4).In the condition when the chamber atmosphere with humidity of 62%RH,the electrolyte film formed on the steel surface after immersion can be maintained only for a shorter period,as a result,the steel surface undergoes distinct dry and wet changes,and the formed rust scale is porous with obviously high amount ofβ-Fe_(3)O_(4)OH,which is of high cathode oxidation activity,thus the steel presents much severe non-uniform corrosion.On the other hand,when the chamber atmosphere with humidity of 83%RH,the corrosion products scale is much dense and uniform with higher amount of Fe_(3)O_(4),therefore,exhibits a blocking effect on the attack of aggressive Cl-to certain extent.