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.