Abstract: Microstructure of a Fe-Mn-Al-C ferrite based lightweight steel after hot-rolling and solution treatment at 850, 950 and 1050 ℃, respectively, were analysed by means of OM, SEM and X-ray diffractometer. The corrosion resistance of the solution treated samples were studied by obtaining the polarization curves, impedance curves and the surface states corrosion in 3.5%NaCl solution. The results show that the microstructure after solution treatment at 850, 950 and 1050 ℃ are ferrite+ κ carbide, ferrite+ austenite+ a little κ carbide and ferrite+ austenite, respectively. With the solution treatment temperature increasing, κ carbides coarse gradually until dissolve completely, austenite forms and the grain grows, but the amount of the austenite decreases slightly. The best corrosion resistance in 3.5%NaCl solution is obtained after solution treatment at 950 ℃, which self corrosion current density is 3.102×10^-6 A/cm² and resistance R_p value of passivation film is 3944 Ω, the corrosion rate is lowest after corrosion test for 240 h. All of that is mainly due to the higher content of austenite and Al in ferrite as well as the lower content of ferrite and κ carbide.

Key words: Fe-Mn-Al-C ferrite based ligh tweight steel, solution treatment, microstructure, corrosion resistance