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

Abstract

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.

Keywords

• 439 ferritic stainless steel|marine atmospheric corrosion|pitting corrosion|electrochemical test|evaluation