Pre-treatments in silicate solutions to mitigate reinforcing steel corrosion in chloride-contaminated environments

Abstract

Silicate ions were incorporated into a pre-treatment to mitigate corrosion in reinforcing steel bars. The efficiency of these pre-treatments was compared by testing steel samples in concrete pore simulating solutions contaminated with chloride ions. The study involved cyclic voltammetry, anodic polarisation curves and weight-loss tests following a 60-day immersion period. Surface analysis included micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrical properties of the film were analyzed by impedance spectroscopy and Mott–Schottky plots. Polarisation curves show higher pitting potentials and lower corrosion current densities when pre-treating with silicate ions. Localised attack appears after 60 days of immersion in solutions containing chloride ions, but weight loss is reduced by 75% for coupons pre-treated in silicate solutions. XPS and Raman spectra indicate that the presence of silicate ions affects the composition of the passive film and the corrosion products. The results show that pre-treatments in silicate solutions are effective to minimise steel corrosion in aggressive environments.