Effects of Cr on pitting corrosion resistance and passive film properties of austenitic Fe–19Mn–12Al–1.5 C lightweight steel

The effects of Cr on microstructure, pitting corrosion resistance, and passive film properties of austenitic Fe–19Mn–12Al–1.5 C–(0–7.3 wt%)Cr lightweight steel were studied. Microstructural analysis indicated that the optimal Cr content for a homogeneous microstructure was 5 wt%. Passive film analysis showed that alloying Cr up to 5 wt% in the matrix increased both the Cr and Al content in the passive film and increased the ratio of oxide to hydroxide in the film. Thus, the Fe–19Mn–12Al–1.5–5 Cr alloy exhibited the highest resistance to pitting corrosion among the investigated alloys due to the homogeneous microstructure and a (Cr,Al)-enriched passive film. • Pitting corrosion resistance of Fe-19Mn-12Al-1.5 C-(0–7 wt%)Cr lightweight steels was studied. • Highest pitting corrosion resistance was obtained in Fe-19Mn-12Al-1.5–5 Cr (wt%) alloy. • All secondary phases of the lightweight steels act as pit initiation sites. • Alloying Cr with the matrix increased the oxide-to-hydroxide ratio of the passive film. • Passive film was enriched with Cr and Al by alloying Cr with the matrix.