Enhanced passivation of Cr-modified rebar in simulated seawater sea-sand concrete chloride environment

This study investigates the enhanced passivation behavior of Cr-modified rebar compared to ordinary carbon rebar in a simulated seawater sea-sand concrete (SSC) chloride environment. The effects of chloride concentration on the morphology and composition of passive films are analyzed, along with the kinetics of film formation and the interaction between the passive film and chloride ions. Results show that Cr-modified rebars exhibit superior passivation, with a higher critical chloride concentration (0.8 M for Cr11 vs. 0.2 M for HRB) and better stability under varying alkalinity. Increased chloride concentration leads to a slight increase in passive film thickness for Cr11, along with Cr diffusion that reduces stratification. The Cr-modified rebars also demonstrate enhanced interfacial adhesion, providing more stability and resistance to degradation. Chloride adsorption weakens the passive film's electronic structure, but Cr-rich regions within the film help mitigate this damage, making the Cr-modified rebars more resistant to corrosion. The findings highlight the potential of Cr-modified rebars as a superior reinforcement material for SSC structures.