Corrosion behaviour of steel rebar: effect of simulated concrete pore solution and chloride ions

Abstract

In this work, we investigate the corrosion behavior of steel rebar (SR) in four simulated concrete pore solutions (CPS): NaOH+KOH (CPS1), Na 2 CO 3 (CPS2), NaOH (CPS3) and Ca(OH) 2 (CPS4) medium.  Effect of addition of Cl - anions as pollutant on pitting and uniform corrosion of SR is investigated by using potentiodynamic polarization (PDP) technic. The result obtained show that uniform and pitting corrosion of SR are strongly influenced by the nature of simulated CPS. In unpolluted CPS’s, only uniform corrosion of SR is observed in all cases. SR has excellent corrosion resistance in CPS4 compared to the other simulated CPS. In the polluted CPS’s by Cl - anions, we observe an accelerated uniform corrosion especially in CPS1, CPS3 and CPS4 mediums. The sensitivity to localized corrosion of SR varies from one simulated environment to another. It has the best resistance to pitting corrosion in polluted CPS3 medium. In CPS1 (pH = 13) and CPS2 (pH = 11.6) polluted by 3% NaCl, the tendency to pitting corrosion is the same. The localized attack is more pronounced in polluted CPS4 (pH=12.7). These results demonstrate that there are no limit values of the pH and the content of Cl - ions for the initiation of pitting and / or uniform corrosion. Therefore, it is the chemical composition of the simulated medium which imposes the pH value and the Cl - content for systematic corrosion study of the SR in the simulated CPS.