Analysis of inhibition of concrete steel-rebar corrosion by Na2Cr2O7 concentrations: Implications for conflicting reports on inhibitor effectiveness

Corrosion test data were measured using non-destructive electrochemical techniques and analysed for studying inhibition effectiveness by different concentrations of Na2Cr2O7 on the corrosion of concrete steel-rebar in NaCl and in H2SO4 media. For these, specifications of ASTM G16-95 R04 were combined with the normal and the Gumbel probability density functions as model analytical methods for addressing issues of conflicting reports of inhibitor effectiveness that had generated concerns. Results show that reinforced concrete samples admixed with concentrations having 4 g (0.012 7 mol), 8 g (0.025 4 mol) and 6 g (0.019 1 mol) Na2Cr2O7 exhibited, in that order, high inhibition effectiveness, with respective efficiency, η, of (90.46±1.30)%, (88.41±2.24)% and (84.87±4.74)%, in the NaCl medium. These exhibit good agreements within replicates and statistical methods for the samples. Also, optimal inhibition effectiveness model in the H 2SO4 medium was exhibited by 8 g (0.025 4 mol) Na 2Cr2O7 concentration having η=(78.44±1.10)%. These bear implications for addressing conflicting test data in the study of effective inhibitors for mitigating steel-rebar corrosion in aggressive environments. © 2013 Central South University Press and Springer-Verlag Berlin Heidelberg