Effect of Tempering Treatment on Atmospheric Corrosion Behavior of 3Cr13 Martensitic Stainless Steel in Marine Environment

In this study, 3Cr13 martensitic stainless steel was tempered to three typical strength grades, and the corresponding atmospheric corrosion behavior in a coastal zone of Wanning, China, was investigated. Electrochemical measurements were taken, and the morphology, composition, and structure of the rust formed after natural exposure were analyzed. The results indicated that different microstructures were obtained by tempering at different temperatures, which affected the corrosion behavior. The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization results show that the 280°C tempered condition was prone to form a better protective passive film compared to the other two higher-temperature tempered conditions. The corrosion rate of 3Cr13 steel tempered at a low temperature of 280°C was markedly lower than that at higher temperatures of 540 and 600°C. The corrosion weight loss of specimens tempered at 540°C and 600°C was over 8 times higher than that of the specimens tempered at 280°C after two years of natural exposure. The thickness of the rust layer formed on the 540- and 600°C-tempered specimens exceeded 40 μm, which was approximately 5 times that of on the 280°C-tempered specimens. The corrosion products formed on tempered 3Cr13 steel were found to vary with the temper conditions. The corrosion products formed on tempered 3Cr13 martensitic stainless steel also varied with the tempering temperature. A rust layer mainly composed of γ-FeOOH and β-FeOOH was formed on 280°C-tempered 3Cr13 steel specimens, while α-FeOOH and Fe3O4 were formed on 540- and 600°C-tempered 3Cr13 steel specimens in addition to γ-FeOOH and β-FeOOH. Distinct pitting corrosion occurred on specimens of all three strength grades specimens during natural exposure. Formation of Cr-rich carbides during high-temperature tempering increased corrosion pit initiation.