Influence of pH on passivation of mild steel in simulated concrete pore solution: Electrochemical, ToF-SIMS and ReaxFF study

The passivation evolution of mild steels in simulated concrete pore solutions with varying pH were systematically investigated in present study. Based on electrochemical, time-of-flight secondary ion mass spectrometry, and ReaxFF molecular dynamics simulation, a plausible model with high logical coherence and theoretical soundness was proposed to elucidate the underlying passivation mechanism. The results depict that the steels within concrete pore solution with high pH facilitates quick and compact film formation, leading to superior passivation performance. Spontaneously-induced passive film of mild steel demonstrates a dual-layer structure composed of an inner layer rich in Fe(II) and an outer layer rich in Fe(III).