Quantitative Judgment Method for Passivation and Depassivation of Reinforcing Steel Bar in Simulated Concrete Solution
YU Bo1,2,3, HUANG Junming1, WAN Weiwei1, YANG Lyufeng1,2,3
1 School of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China 2 Key Laboratory of Engineering Disaster Prevention and Structural Safety of Ministry of Education, Nanning 530004, China 3 Guangxi Key Laboratory of Disaster Prevention and Engineering Safety, Nanning 530004, China
Abstract: Based on the passivation and depassivation experiments of reinforcing steel bar in simulated concrete solution, the corrosion electrochemical parameters of reinforcing steel bar during the passivation and depassivation processes were systematically investigated. Meanwhile, the quantitative judgment method for the passivation and depassivation process of reinforcing steel bar in simulated concrete solution was proposed. Simulated concrete solution and reinforcement electrode were prepared first. Then the variation of corrosion electrochemical parameters (including the open circuit potential, polarization resistance and corrosion current density) of reinforcing steel bar during passivation and depassivation process were tested by means of the half-cell potential method, the electrochemical impedance spectroscopy and the dynamic potential polarization method with the saturated calomel electrode and mercury/oxide mercury electrode as the reference electrode respectively. Finally, the quantitative judgment method for the passivation and depassivation process of reinforcing steel bar in simulated concrete solution was presented, and the critical chloride content of reinforcing steel bars during depassivation process was determined. Analysis results show that it takes about 5 days for reinforcing steel bar to complete the passivation and to form a stable passivation film during the passivation process, when the relative variation rate of open circuit potential, polarization resistance and corrosion current density along with time lower than 10% and tend to be stable. Depassivation of reinforcing steel bar will occur when the relative variation rate of open circuit potential, polarization resistance and corrosion current density along with chloride content greater than 30%, 50% and 150% respectively. The critical chloride content for depassivation of reinforcing steel bar is about 0.12 mol/L in the simulated concrete solution.
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2020, Vol. 34 
