Experimental and ReaxFF MD study on Cr10Mo steel passivation in simulated concrete pore solutions

In this paper, the passivation evolution and mechanisms of a novel Cr10Mo steel in simulated concrete pore solutions with varying pH levels (12.4, 12.9, and 13.5) are investigated using electrochemical methods, Pourbaix analysis, and ReaxFF molecular dynamics (MD) simulations. The findings reveal that Cr10Mo steel undergoes spontaneous passivation in all simulated solutions, forming a bi-layered passivation film composed of inner Cr 2 O 3 and outer Fe 2 O 3 layers. However, lower pH values promote the formation of chromium oxides/hydroxides, resulting in thicker and more stable passivation films. Conversely, higher pH values diminish open circuit potential and linear polarization resistance, thereby compromising the corrosion resistance of passivated Cr10Mo steel. Experimental X-ray photoelectron spectroscopy observations and ReaxFF MD simulations corroborate this seemingly paradoxical phenomenon. The fundamental mechanism likely involves pH-sensitive selective generation of Cr(OH) 3 , which transforms into Cr 2 O 3 or Cr 2 O 4 2- .