439铁素体不锈钢在典型海洋大气环境中的腐蚀行为

Corrosion Behavior of 439 Ferritic Stainless Steel in Typical Marine Atmospheric Environment

为研究新型439铁素体不锈钢在海洋大气环境中的腐蚀行为,在典型海洋大气环境的海南文昌试验站、山东青岛试验站和对照的内陆城市大气环境湖北武汉试验站分别投放439不锈钢试样进行大气曝晒试验。对取回的2 a曝晒后试样进行电化学试验测试,结合超景深显微镜、扫描电子显微镜以及EDS能谱仪进行分析。试验结果表明:439不锈钢在大气环境中曝晒后的主要腐蚀形式为点蚀,其中文昌地区曝晒后的腐蚀程度最高,腐蚀产物主要为铁的氧化物,且曝晒后试样在3.5%(质量分数)的NaCl溶液中仍具有钝化能力,电化学试验结果经分析后与宏微观形貌判断结果一致,即文昌地区试样腐蚀程度最高,腐蚀电位最低,表明钝化膜稳定性最差;山东青岛试验站试样腐蚀也较为严重,而内陆城市大气环境的武汉试验站试样腐蚀程度最低。

In order to study the corrosion behavior of a new type of 439 ferritic stainless steel in marine atmospheric environment,439 stainless steel samples were put into two test stations in typical marine atmospheric environment(Wenchang test station and Qingdao test station)and one inland urban atmospheric environment(Wuhan test station)for atmospheric exposure test.After two years of exposure,the samples were tested by electrochemical test and analyzed by ultra depth of field microscope,scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).Results showed that the main corrosion form of 439 stainless steel in atmospheric environment was pitting corrosion,and the corrosion degree in Wenchang area was the highest.Meanwhile,the corrosion products were mainly composed of iron oxides,and the samples still had passivation ability in 3.5%(mass fraction)NaCl solution after exposure.The electrochemical test results were consistent with the macro and micro morphology judgment results,i.e.,the samples in Wenchang area corroded most seriously and had the lowest corrosion potential,revealing that the stability of the passive film on those samples was the worst.The samples in Qingdao test station also corroded seriously,while those in Wuhan test station had the lowest corrosion degree.