Abstract
Dual phase steels have been widely used in the automotive industry to produce lighter weight vehicles to meet stringent safety and fuel economy regulations. While galvanic corrosion resulting from dissimilar ferrite and martensite phases has been reported, little is known about the corrosion behavior of dual phase steel coupled to a dissimilar metal under corrosive environments. A fundamental study was undertaken to understand the corrosion behaviors of dual phase steel under coupling conditions in NaCl solution. The results show that dual phase steel has a corrosion potential between carbon steel and martensitic steel. Galvanic action between the ferrite and martensite phases leads to selective corrosion of ferrite phase in NaCl solution. When coupled to more noble Ni, dissolution takes place in both ferrite and martensite phases, and ferrite phase dissolves faster. When coupled to less noble Zn, a minor amount of hydrogen resulting from corrosion of a steel-Zn coupling is found to diffuse into the steel.