Role of Manganese Sulfide Inclusions in Steel Rebar in the Formation and Breakdown of Passive Films in Concrete Pore Solutions

This study examined manganese sulfide (MnS) inclusions in
steel rebar exposed to a simulated concrete pore solution to
understand their role in passive film, corrosion, and pit propagation behavior. The passive film was characterized using x-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and electrochemical techniques. The results showed that MnS inclusions adversely affected the nature of the passive film and accelerated corrosion and pit formation. A schematic model was developed to explain the deterioration of passive film formed on steel containing MnS inclusions, and was validated by Raman spectroscopy of the resulting rust formed on such steel.