Carbon steel passivity examined in solutions with a low degree of carbonation: The effect of chloride and nitrite ions

M.B. VALCARCE; M. VAZQUEZ

MATERIALS CHEMISTRY AND PHYSICS

Elsevier

Lugar: Amsterdam; Año: 2009 vol. 115 p. 313 - 321

0254-0584

This work is focused on investigating the effect of nitrite ions as inhibitors against steel corrosion in carbonated (pH=9) and chloride-contaminated concrete pore simulating solutions. Various inhibitor dosages, together with two chloride contents are tested. The inhibition efficiency is evaluated on steel electrodes, measuring electrochemical parameters such as corrosion potential, cyclic voltammograms, anodic polarization curves, pitting and repassivation potentials, polarization resistance and performing electrochemical impedance spectra, together with weight-loss measurements after a 30-days immersion period. Independently of the chloride content, carbon steel presented the best behavior when [NO2-] = 0.2 mol l-1. In this case, the inhibition efficiency reaches 99% and after pitting attack, surface repassivation is possible. To high chloride ions when inadequate dosages of inhibitor are used, the risk of pitting attack is higher because Epit is close to the OCP. The [NO2-]/[Cl-] ratio is not an appropriate parameter to evaluate the inhibitor efficiency for different chloride concentrations in a carbonated concrete.