The efficiency of eco-friendly corrosion inhibitors in protecting steel reinforcement

Abstract

Reinforcing steel is used extensively in buildings to provide strength and integrity to the concrete structure. This material is, however, highly susceptible to corrosion in chloride-contaminated environments, which increases the risk of structural instability and failure. This work characterises the mechanisms and efficiency of corrosion protection offered by sodium nitrate, casein, and two amino acids (11–aminoundecanoic acid, and p–aminobenzoic acid) in simulated concrete pore solutions with different contents of chloride ions. The performance of each inhibitor in the critical chloride concentration (Ccirt) was investigated using electrochemical techniques. Open circuit potential and linear polarisation were used to identify the Ccrit in synthetic pore solutions. Potentiodynamic polarisation and electrochemical impedance spectroscopy were performed to evaluate the corrosion activities and the passivation mechanism of inhibitors in Ccrit. Results indicate that reinforcing steel can be protected through an appropriate selection of corrosion inhibitors. Among of the inhibitors studied here, casein demonstrated the highest corrosion inhibition efficiency with minimum current density of 9.19 × 10−8 μA/cm2 and inhibitor efficiency of more than 80%. Casein provides passivity to the reinforcing steel in the presence of the Ccirt in the pore solution.