Interactions between nitrites and Fe(II)-containing phases during corrosion of iron in concrete-simulating electrolytes

• Published in: Journal of materials science 2006-08, Vol.41 (15), p.4928-4936
• Main Authors: DHOUIBI, L, REFAIT, Ph, TRIKI, E, GENIN, J.-M. R
• Format: Article
• Language: English
• Subjects: Applied sciences; Concretes; Corrosion; Corrosion environments; Corrosion inhibitors; Corrosion potential; Corrosion products; Corrosion rate; Corrosion tests; Electrode polarization; Electrolytes; Exact sciences and technology; Ferrous hydroxide; Foils; Inhibition; Iron; Iron carbonate; Materials science; Metals. Metallurgy; Mossbauer spectroscopy; Nitrites; Nitrogen dioxide; Oxidation; Pitting (corrosion); Pitting potential; Sodium nitrite; Spectrum analysis
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-006-0332-0

The influence of sodium nitrite on the corrosion processes of iron in solutions simulating polluted concrete was investigated by means of electrochemical methods, such us potentiodynamic, galvanostatic and impedance spectroscopy tests, coupled with analyses of the corrosion layers by Mössbauer spectroscopy. NO2− ions are anodic inhibitors and provoked consequently an important increase of the corrosion potential. The polarisation curves show that NO2− ions increase the pitting potential value. The size of electrochemical impedance spectra obtained at the OCP increases with the concentration of nitrite, which confirms the decrease of the corrosion rate. Galvanostatic experiments allowed us to provoke active corrosion even in presence of NO2−. When nitrite ions are not present, the corrosion products mainly consist of iron (II) compounds, FeCO3 or Fe(OH)2 depending on the pH, and iron(II)–iron (III) compounds, i.e. green rusts (GRs). The main effect of nitrite ions was to accelerate the oxidation of GRs into FeOOH phases, confirming their oxidizing role. While immersed for long periods in the nitrite containing solutions, the α-iron foils do not present any single trace of corrosion.