Corrosion of carbon steels subjected to chloride and sulfate in simulated concrete pore solutions with different pH

The present study explores low-carbon steel corrosion in simulated concrete pore solutions with varying pH, focusing on the influence of chloride and/or sulfate ions. Employing electrochemical techniques, ToF-SIMS, XRD and DFT calculations, the results reveals that higher pH strengthens the passivation film and reduces corrosion by limiting corrosive ions adsorption. Notably, sulfate triggers corrosion at higher thresholds, while chloride alone significantly elevates corrosion rates. The presence of both ions shows mitigated corrosion risk due to competitive absorption onto steel interface of sulfate. The two-stage mechanism involving competitive adsorption and catalytic corrosion is initially proposed and elucidates the interaction mechanism of chloride and sulfate during steel corrosion process.