Microelectrochemistry of dual-phase steel corroding in 0.1 M sulfuric acid

Corrosion behavior of high-purity dual-phase carbon steel composed of only ferrite and martensite phases in 0.1 M sulfuric acid was investigated by both macro- and micro-electrochemical methods. The dual-phase steel corrodes non-uniformly due to galvanic coupling between its microstructures as well as self-corrosion of each phase. Hydrogen evolution reaction on galvanic-coupled martensite accelerates iron dissolution reaction of ferrite, though the corrosion rate of martensite was three-times larger than that of ferrite due to the self-corrosion in the acid. Totally, ferrite phases corrode selectively and the degree of selective corrosion was about two-times larger than martensite phases.