Research on Local Corrosion Behavior of High Manganese Austenitic Steel

The effects of adding oxidant to 3.5%NaCl solution and sensitization treatment on the local corrosion properties of high manganese steel are studied by using alternate immersion corrosion test, polarization curve test, scanning observation (SEM) and transmission electron microscope observation (TEM). The results show that after the alternate immersion corrosion test, all the samples show the morphologies of overall non-uniform corrosion and local pitting corrosion. The rust layer on the surface of the sample is loose after corrosion in 3.5% NaCl solution. The self-corrosion current density increases by two orders of magnitude in initial stage in 3.5%NaCl+0.25%Na₂S₂O₈ solution, which produces dense rust layer in a short time and prevents corrosion from spreading to the inner layer. The average corrosion rate and the depth of pitting corrosion are reduced. The microstructure of high manganese steel has not changed, carbides precipitated discontinues at the grain boundary after sensitization treatment at 800 ℃ for 5 hours, but the corrosion resistance of the sensitized state is equivalent to that of the original state. The polarization curve confirms the experimental results.