Effect of micro-alloying with cr, n and al on corrosion resistance of high manganese austenitic steel in acidic salt spray environment

To further enhance the corrosion resistance of high manganese steel, the effect of adding micro-alloying elements such as Cr, N, and Al on the corrosion process and electrochemical properties of fully austenitic high manganese steel (HMS) in acidic salt spray environment was investigated. The corrosion performance and corrosion products of the HMS were assessed by means of mass loss method, field emission scanning electron microscopy (SEM), and white light interferometry, and the evolution of electrochemical properties of two HMSs (namely the micro-alloyed HMS (WH-HMS) and the un-alloyed HMS (PT-HMS)) was examined by electrochemical techniques such as dynamic potential polarization and AC impedance spectroscopy. The results show that with the prolongation of corrosion time, the formed oxide scale on Micro-alloyed HMS becomes much more compact and has much better corrosion resistance for long-cycle corrosion. The corrosion kinetics of the micro-alloyed high Mn steels follows ΔW_WH = 4.44202 × 10^-4 t^0.9618, in the contrast, the un-alloyed HMS follows ΔW_PT = 8.74985 × 10^-4 t^0.67759. The electrochemical results show that the corrosion current density of the two HMSs gradually decreases with increasing corrosion time, and the capacitive arc gradually increases. After 240 h corrosion, the micro- alloyed HMS presents the capacitive arc much greater than that of the untreated HMS, whereas the corresponding corrosion rate of 1.925 × 10^-3 mm/a for the former is less than that of the later. The main reason for the better corrosion resistance of the micro-alloyed high manganese steel is that the micro-alloying of Cr, N, and Al reduces the precipitation of carbides within high manganese steel, the formed oxide scale is much compact with good adhesion to the substrate, therefore which can effectively hinder the attack of Cl- and thus provide better protectiveness for the micro-alloyed HMS.