Study on the Relationship Between Humidity and Under-Deposit Corrosion in High Strength Medium Manganese Steel

This study examines the behavior of under-deposit corrosion in M10C medium manganese steel when subjected to three distinct levels of relative humidity—60%, 80%, and 100%. The research employs X-ray diffraction, scanning electron microscopy, and confocal laser scanning microscopy to observe and statistically analyze the corrosion product phases, corrosion product morphology, and maximum pit dimensions on the sample surfaces. The results indicate that under-deposit corrosion occurs only when the relative humidity reaches a critical threshold value, which falls between 60 and 80%. This phenomenon is attributed to the hygroscopic dissolution of NaCl particles within the deposit layer, as they absorb sufficient moisture from the surrounding air, leading to the formation of a corrosive thin liquid film on the surface of the medium manganese steel. As the relative humidity increases, medium manganese steel under-deposit corrosion develops faster and corrosion is more pronounced. Under 100% relative humidity conditions, the medium manganese steel is most susceptible to pitting corrosion.