Comparative Corrosion Behavior of Five Microstructures (Pearlite, Bainite, Spheroidized, Martensite, and Tempered Marten
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UCTION
CORROSION of steel is a major problem in the petroleum, chemical, automotive, and construction industries. Corrosion of steel depends on several factors, such as environment, material composition, and microstructure. These factors are also crucial in deciding the life of the components.[1] Microstructure and composition play a very important role in deciding the corrosion susceptibility of steel, as reported by several researchers.[2–16] Clover et al.[17] showed that the tempered martensite has a higher corrosion rate than the ferrite/pearlite microstructure in the stirred autoclave operating with a CO2 environment. Kazum et al.[13] reported a higher corrosion rate for a martensitic steel than that of a nanostructured bainitic steel in 3.5 pct NaCl solution. The nanostructured bainitic steel shows only general corrosion, whereas the martensitic steel reveals a high rate of localized corrosion. Cleary and Greene[16] reported a lower corrosion rate for a spheroidized steel in 0.1N H2SO4 as compared to an annealed as well as
PRVAN KUMAR KATIYAR and K. MONDAL are with the Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208 016, India. Contact email: [email protected] S. MISRA is with the Department of Civil Engineering, Indian Institute of Technology, Kanpur 208 016, India. Manuscript submitted March 1, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
water-quenched steel. In addition, the corrosion rate decreases with the increase in the cementite particle size in the spheroidized steel. Moon et al.[4] showed that, in 3.5 pct NaCl solution, conventional C-Mn pearlitic steel exhibits lower corrosion current density than does bainitic steel. Balasubramaniam et al.[2] observed that the pearlitic steel with microalloying (Cr-Cu-Ni (NCC)) elements shows better crevice corrosion resistance as compared to the conventional C-Mn pearlitic steel in 3.5 pct NaCl + 3.5 pct FeCl3 solution. Moon et al. also reported higher polarization resistance for the NCC normalized rail steel than that of the conventional C-Mn steel in a solution of 3.5 pct NaCl because the pearlitic spacing of the C-Mn steel is coarser as compared to the NCC normalized steel. The steel with 0.7 wt pct carbon is predominantly used in making rail, spring, and cutting tools. The electrochemical properties of high carbon steel depend heavily on the morphology of cementite (Fe3C) in the ferrite matrix.[16] On the other hand, for the same composition of steel, the microstructure and, subsequently, size, shape, and distribution of different phases can be altered by various heat treatment practices, such as normalizing, isothermal transformation, spheroidizing, oil quenching, and tempering.[17–19] Hence, it would be interesting to see the effect of different microstructures made from a single composition of steel on the electrochemical behavior. Despite recognizing the importance of the morphology of microstructure on the corrosion susceptibility of steel,[2–17,20–25] not much work is reported in the
literature where, fo
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