Silicate Ions as Corrosion Inhibitors for Carbon Steel in Chloride-Contaminated Concrete Pore Simulating Solutions

Silicate ions were tested as corrosion inhibitors for construction steel using concrete pore simulating solutions contaminated with chloride ions. The results were compared to those from solutions with no silicate and with no silicate and no chloride ions. The evaluation included typical electrochemical techniques such as cyclic voltammetry, polarization curves, and weight loss evaluation after a 60 day immersion. Surface analysis was undertaken using micro-Raman spectroscopy and x-ray photoelectron spectroscopy (XPS). Polarization curves showed no sign of pitting and low corrosion current densities if silicate ions were present, even when chloride ions were also in the system. In parallel, no localized attack was observed after 60 days of immersion in solutions containing an inhibitor/chloride = 1 ratio. Cyclic voltammograms and XPS spectra indicated that the presence of silicate ions affects the composition and thickness of the passive film: the film becomes thinner and contains more Fe(II) species. All of the results showed that silicate ions act as promising inhibiting agents.