Effect of microstructure on corrosion behavior of dual-phase steels

Dual phase (DP) steels with different volume fractions of martensite and epitaxial ferrite were produced in different intercritical annealing temperatures and cooling rates. Corrosion behaviors of four different DP steels were investigated in 3.5 % NaCl solution by using potentiodynamic polarization and immersion tests. The results showed that both amounts of martensite and epitaxial ferrite have an influence on the corrosion behavior of DP steels. It was observed that corrosion resistance increased considerably with the presence of epitaxial ferrite as compared to dual phase steel containing non-epitaxial ferrite. On the other hand, the corrosion resistance of DP steels decreased with an increase in the martensite volume fraction (MVF).