INVESTIGADORES
YOHAI DEL CERRO lucia
congresos y reuniones científicas
Título:
The Role of Chloride, Phosphate and Carbonate Ions on Carbon Steel Passivity Studied in Simulating Concrete Pore Solutions.
Autor/es:
EVELYN TOLOSA; M.A. FRONTINI; L. YOHAI; M. VÁZQUEZ; M.B. VALCARCE
Lugar:
Sevilla
Reunión:
Congreso; EUROCORR 2019; 2019
Institución organizadora:
European Federation of Corrosion
Resumen:
Corrosion of constructional steel is one of the main pathologies affecting life extension in reinforced concrete. To mitigate the effect of aggressive environments, phosphate ions can be used as corrosion inhibitors, favoring the formation of a compact and adherent passive layer composed by iron oxides and iron phosphates. The effect of phosphate ions on the protective properties of passive films formed in carbonated concrete (pH = 9) is evaluated. Anodic polarization curves, Mott-Schottky plots and weight loss test are performed. The inhibitor/chloride ratios tested are 1, 0.6 and 0.2. All the experimental work is carried out in a solution that simulates the composition of the pores in chloride contaminated carbonated concrete. Two carbonate contents are analyzed: low carbonated solutions (LCS) contain ([HCO3-] + [CO3-2]) = 0.0315 mol L-1 and high carbonated solutions contain ([HCO3- ] + [CO3-2]) = 0.315 mol L-1. Both electrolytes include NaCl (0.1 mol L-1), resulting in [Cl-]/[OH-]=10000. The results indicate that steel is passive in HCS and active in LCS. However, passivity is regained in LCS when phosphate ions are incorporated. Mott-Schottky plots indicate that the passivating film behaves as an n-type semiconductor. Donor density values are similar in LCS and HCS when phosphate/chloride ratio is 1. After 30 days at open circuit potential, localized attack is not observed with 1 and 0.6 inhibitor/chloride ratios, accompanied by corrosion efficiencies higher than 99%. However, when inhibitor/chloride = 0.2, pitting attack is observed. Raman results show a wide band at 982 cm-1 in LCS when inhibitor/chloride = 1, associated to the presence of phosphate ions in the passive layer. In contrast, this is not observed in HCS, probably because the passive layer is thinner.
