Effect of chemical composition and plastic deformation on corrosion properties of high-Mn austenitic steels in alkaline solution

Purpose: The aim of the paper is to compare the corrosion properties of two high-Mn austenitic steels with various Al and Si additions in 0.1M NaOH solution using a potentiodynamic method. Design/methodology/approach: The steels used for the investigation were thermomechanically rolled in 3 passes. The final thickness of about 2 mm was obtained at a temperature of 850°C. Three groups of samples were prepared: thermomechanically rolled, thermomechanically rolled and additionally annealed at 900°C for 20 min, thermomechanically rolled and additionally cold deformed in static tensile test to total elongation of 36%. Corrosion resistance of investigated steels was examined using the potentiodynamic method. The metallographic inspection of corrosion damage included scanning electron microscope observations. The chemical analyses of the corrosion pits were carried out using EDS techniques. Findings: It was found that X4MnSiAlNbTi27-4-2 and X6MnSiAlNbTi26-3-3 steels were characterized by relatively high corrosion resistance in 0.1M NaOH solution independently of their state. EDS analysis revealed that corrosion pits nucleated preferentially at nonmetallic inclusions such as MnS and AlN. Results of potentiodynamic tests showed that cold deformation had the highest influence on decreasing the corrosion resistance of investigated steels. Thermomechanically treated and supersaturated specimens showed lower values of corrosion current density and consequently less amount of corrosion damage. Research limitations/implications: To investigate in more detail the corrosion behaviour of high-manganese austenitic steels, the impedance spectroscopy investigations will be carried out. Practical implications: The knowledge of the corrosion resistance of high-Mn steels has a significant effect on their industrial application in the automotive industry. Originality/value: The corrosion resistance of two high-manganese austenitic steels with different initial microstructures was compared in alkaline solution.