Study On Corrosion Inhibitors For Reinforcing Steel And Electrochemical Chloride Extraction Applied To Reinforced Concrete Structures

Reinforcing steel corrosion is the major cause of premature degradation of concrete structures and has been a serious and significant problem in modern society. Cl^-ingress is the main cause of reinforcing steel corrosion. It is very significant to study the corrosion and protection of reinforcing steel in chloride-contaminated concrete. The aim of this work is to study the corrosion mechanism of reinforcing steel, explore corrosion inhibitors and electrochemical chloride extraction (ECE) technique for chloride-contaminated reinforced concrete, which is valuable and significant both in science and practice. The main results are as follows:1. Some corrosion inhibitors for reinforcing steel have been investigated, and the good inhibiting effect of D-sodium gluconate has been found.The inhibiting effect of sodium benzoate,β-sodium glycerophosphate, ethanolamine and D-sodium gluconate on the reinforcing steel immersed in the simulated concrete pore solution (SPS) with 0.1mol·L^-1NaCl has been studied by EIS and other electrochemical techniques, respectively. With the concentration of 0.1mol·L^-1, sodium benzoate andβ-sodium glycerophosphate show obvious inhibiting effect, respectively. And D-sodium gluconate with the concentration ranged from 0.001 to 0.1mol·L^-1 has excellent inhibiting effect.Moreover, D-sodium gluconate was mixed with other substances and used as corrosion inhibiting admixtures. The admixture of D-sodium gluconate and sodium tetraborate has the best inhibiting effect among these mixed inhibitors. In addition, the admixtures of D-sodium gluconate and glycin, D-sodium gluconate and ethanolamine have good inhibiting effect, too.2. Corrosion inhibition and mechanism of reinforcing steel by D-sodium gluconate has been studied.D-sodium gluconate can effectively inhibit the initiation of the reinforcing steel corrosion in SPS containing Cl^-, mainly by suppressing the anodic reactions. The inhibition mechanism can be explained on the basis of the competitive adsorption between gluconate anions and Cl^- on the reinforcing steel surface. And gluconate anions can eventually form a compact adsorptive film by strong chelation and effectively inhibit the initiation of reinforcing steel corrosion.3. Electrochemical chloride extraction (ECE) technique has been developed.The ECE instrument for reinforced concrete has been designed and set up in the laboratory. The electrochemical treatment was performed using a cathodic current with platinized titanium mesh as the external anode. Ag/AgCl electrodes as Cl^- probe were embedded at the different distance from the steel/concrete interface in concrete. The ECE technique set-up is able to reduce the Cl^- concentrations in concrete effectively, and mitigate the corrosion of reinforcing steel.