Corrosion inhibitor efficiency rating to concrete in environments contaminated with CO2 and chloride ions

Abstract

The objective of this study was to evaluate, through electrochemical techniques, the behavior and efficiency of three corrosion inhibitors for concrete in marine environments and contamination from carbon dioxide (CO2). The synthetic inhibitor of sodium nitrite (SN) and the commercial inhibitors nitrite salts (NIS) and organic and inorganic compounds (OIC) were tested at the concentrations of 2, 3 and 4% (m.V-1). Electrochemical tests were carried out to assess the effectiveness of inhibitors against corrosion caused by chloride ions along with the effect of carbon dioxide gas. In these tests, a simulated pore solution (SPS) was used, which represents the electrochemical characteristics of the concrete, adding chloride and bubbling the CO2 gas until the achievement of a pH approximately 7. This procedure was used to simulate the carbonation of the concrete. In environments with CO2, where there was a drop in pH to around 7, the inhibitors NTS and SNI showed a small passivation domain. This occurred for the inhibitor SN in all tested concentrations and with the NIS inhibitor it occurred in concentrations above 2% (m.V-1). For the OIC inhibitor, the 1020 steel showed active dissolution in all tested concentrations, ie. is a passivation domain was not observed in these conditions with CO2 gas. Impedance tests showed less resistance to polarization for the solutions with CO2 and NaCl, in the absence and in the presence of inhibitors.