Effect of chromium on the decarburization and corrosion properties of carbon steels

Full text of publication follows: Effect of 0.3-0.4 wt.%. chromium addition on the decarburization and corrosion behaviour of SA-106 carbon steel was investigated by performing microstructural analysis and electrochemical measurements. SA-106 is an ASME specification for seamless carbon steel pipe for high-temperature service. Optical microscopy, scanning electron microscopy and energy dispersive analysis spectroscopy were performed to clarify the change of de-carburized layer in the carbon steel with different chromium contents after decarburization heat treatment. The experimental results show that the de-carburized layer in the specimen containing 0.3-0.4 wt.%. chromium is much thinner than that in the specimen without chromium. Both specimens with and without chromium have oxide films along the grain boundaries after decarburization heat treatment for 24 hours. These microstructural and compositional differences change the electrochemical corrosion potential and re-passivation behaviour of the SA-106 specimens. (authors)