Role of Martensite Structural Characteristics on Corrosion Features in Ni-Advanced Dual-Phase Low-Alloy Steels

The relationship between the corrosion resistance and martensite structure of Ni-advanced dual-phase weathering steel was studied using transmission electron microscopy, scanning electron microscopy, electrochemical analysis, and atomic force microscopy. The investigations indicate that the final microstructure of the dual-phase weathering steel was composed of a large amount of low-carbon lath martensite distributed in the ferrite matrix. The potential of the martensite phase is higher than that of ferrite, which acts as a microcathode. As the martensite volume fraction in the Ni-advanced dual-phase weathering steel increased, the corrosion rate increased owing to the greater galvanic couple formed between the ferrite and martensite from the increasing ratio of the cathode area to the anode area. In addition, this work provides a method to obtain advanced weathering steel with improved mechanical properties and corrosion resistance.