Corrosion Rate and Noise Resistance Correlation from NaNO2-Admixed Steel-Reinforced Concrete

Abstract

The lack of correlation from measurements of corrosion potential with corrosion rate in corrosion monitoring of steel-reinforced concrete has constituted concerns instigating demands for further experiments or additional monitoring techniques in corrosion studies. This paper studies correlation of corrosion rate from linear polarization resistance instrument and noise resistance from the ratio of standard deviations of corrosion potential to that of corrosion current measured from NaNO2-admixed steel-reinforced concrete in 3.5% NaCl. Different concentrations of NaNO2 were admixed in replicates of steel-reinforced concretes immersed in the saline/marine simulating test-solution and corrosion of the embedded steel-rebar were monitored using the three different, non-destructive, electrochemical methods. Measurements of corrosion test-data from these were subjected to the descriptive statistics of the Weibull distribution function, for which test-data compatibility was ascertained using the Kolmogorov-Smirnov goodness-of-fit statistics. The analysed results of the measured corrosion test-variables, exhibited good correlation between the corrosion rate, as the dependent variable and the function of the admixed NaNO2 molar concentration and the noise resistance, as independent variables. Both experimental and prediction, from correlation fitting, models identified 0.1208 M NaNO2, the optimal concentration employed in the study, with optimum effectiveness, of η>90%, at inhibiting steel-rebar corrosion in the corrosive solution of concrete test-immersion. These bear suggestions of the suitability of the analysed more easily measured corrosion potential and corrosion current for indicating the corrosion activity of steel-reinforcement in concrete designed for corrosive service-environments.