Optimized corrosion performance of a carbon steel in dilute sulfuric acid through heat treatment

Corrosion performance of pearlitic-ferritic carbon steel A179 was compared to its spheroidized condition in contact with 0.5M H2SO4 using a combination of microstructural and electrochemical investigations. Results confirmed a more heterogeneous microstructure with fine ferrite and pearlite grains, increased grain boundary length per unit area and lattice defects (due to lattice strain) for the pearlitic metal compared to the spheroidized condition. Electrochemical measurements then showed different mechanisms for the corrosion of the metal samples. Polarization resistance was lower in the pearlitic condition with localized attack sites and high amounts of surface deposits. Spheroidization treatment was, on the other hand, found to result in 21 times reduction in the corrosion rate because of the development of a homogeneous microstructure.