Pitting corrosion behavior in advanced high strength steels

•The density of inclusions was high in an order of DP, TWIP, and TRIP steels.•TRIP and TWIP steels exhibited complex inclusions as well as single inclusions.•DP steel had the lowest resistance to pitting corrosion.•Initial pits occurred at the MnS particles of complex inclusions in TRIP steel.•Initial pits formed at the Mn oxy-sulfide of complex inclusions in TWIP steel. The type and size of inclusions and their pitting corrosion behavior in dual-phase (DP), transformation-induced plasticity (TRIP), and twinning-induced plasticity (TWIP) steels were investigated. Whereas DP steel had single MnS inclusions, TRIP and TWIP steels had the complex inclusions of MnS and Al2O3, and MnS and Mn oxy-sulfide, respectively. TWIP steel had the most wide size distribution and the largest average size of inclusions. DP steel exhibited the lowest resistance to pitting corrosion due to the high density of inclusions. MnS inclusions in TRIP steel and Mn oxy-sulfide inclusions in TWIP steel acted as a galvanic anode in complex inclusions.