Study on electrochemical corrosion dynamics of cathode dic shield in concrete crack

Abstract

Corrosion of steel reinforcement is a primary factor that negatively impacts the service life and safety of bridges made of concrete. Cathodic protection techniques are widely used to protect reinforcing bars in concrete against corrosion. However, it is inevitable that corrosion cracks will develop in the concrete during long-Term operation, which will significantly shorten the cathodic current protection distance and increase the degree of corrosion of the rebar within the cracks. Therefore, electrochemical experiments and characterization of corrosion forms were carried out based on the company's design of a rectangular connection device, we studied HRB500 steel in 3 wt.% corrosion behavior in rectangular joints under different CP current densities in NaCl solution. The results showed that with increasing experimental time, the corrosion in the crevice transitioned from activation corrosion to oxygen concentration corrosion, with the open-pore potential of the HRB500 steel inside the crevice appearing as a positive shift and the open-pore potential outside the crevice shifting from positive to negative. When implementing cathodic protection, the corrosion of HRB500 steel within the crevice is activated, while the corrosion outside the crevice changes from anodic to mixed controlled corrosion and from full to pitting corrosion. With the increase of CP current density, the corrosion process of HRB500 steel outside the gap is mainly dominated by cathode control, then gradually weakens, and the corrosion form changes from pitting to comprehensive corrosion.