New insights for composition design: A novel synergistic corrosion-resistant effect of Fe–Mn–Al–Cr–Si–Mo–C lightweight steel in 3.5 wt% NaCl solution

Nowadays, a good corrosion resistance of lightweight steel is demanded for its application. However, due to the high contents of Mn and C, which are always corrosion-susceptible elements in steels, the conventional lightweight steel is not desirable for this mission. Although Cr is widely believed to be a common alloying element to improve the corrosion resistance of most steels, it is considered to be ineligible using in the lightweight steel due to the relatively high content of C. This is because the trade-off between corrosion resistance and mechanical properties by alloying Cr. In recent years, the rapid developments of additive and coating manufacturing have provided new possibilities for both the Cr alloying and microstructural modulation to improve corrosion resistance of lightweight steel. In this case, to design a certain chemical composition using in additive and coating manufacturing, it is interesting to clarify the effects of Cr alloying on the corrosion resistance of lightweight steel. To reveal it, in the present work, the Fe–Mn–Al–Cr–Si–Mo–C lightweight steel alloyed with Cr contents of 4 wt%, 8 wt% and 12 wt% are prepared. The corrosion resistances and mechanisms of Cr-alloyed lightweight steels in 3.5 wt% NaCl solution are investigated by electrochemical and immersion tests. The present work may provide new insights for the composition design of lightweight steel, especially for the directions of additive and coating manufacturing.