Effect of ethylenediaminetetraacetic disodium dihydrate and sodium nitrite admixtures on steel-rebar corrosion in concrete

This study investigates effect of different concentrations of ethylenediaminetetraacetic disodium dihydrate (EDTA-Na2: C 10H14N2Na2O8.2H 2O) and sodium nitrite (NaNO2) admixtures, individually or in synergistic/partial NaNO2 replacement model, on the corrosion of concrete steel-rebar in NaCl and in H2SO4 media. Electrochemical monitoring techniques were employed for 48 steel-reinforced concrete samples immersed in the saline/marine and microbial/industrial simulating test environments for 96 days. These test data were subjected to the analyses of the Normal and the Weibull distribution fitting models, for each of which goodness of their fitting the electrochemical test data were studied using the Kolmogorov-Smirnov test statistics. Analysed results showed that EDTA-Na2 admixture concentrations exhibited better inhibition effectiveness, with relatively good effectiveness in their synergistic admixtures, than their equal-mass NaNO2 counterparts in both corrosive environments. Also, post-electrochemical experiment subjection of the concrete samples to testing and analyses of ASTM C39/C39M-03 and ASTM C267-01 showed that use of the optimally inhibiting 8 g EDTA-Na2 (per 2 × 10-3m3 concrete) culminates in gross reduction in compressive strength of concretes in both test-media. However, lowered EDTA-Na2 concentrations exhibited better strength improvements with high corrosion inhibition in the test environments. These suggest suitability of EDTA-Na2 as an environmental-friendly NaNO2 alternative for inhibiting steel-rebar corrosion in saline/marine and microbial/industrial environments. © 2013 Copyright Taylor and Francis Group, LLC