The corrosion of reinforcement steel present under different conditions namely bare steel (SI), steel incement mortar (SII), and steel in cement mortar containing polycarboxylate superplasticizer (SIII) wasinvestigated in 3.5 % sodium chloride solution using potentiodynamic polarization and electrochemicalimpedance spectroscopy (EIS) techniques. The polarization results showed thatthe corrosion rate ofsteel in a mortar containing superplasticizer is much less than that of steel in mortar only or that ofuncovered steel surface, i.e. the corrosion rate follows the order SIII< SII< SI. Also, the results of EISspectra revealed that the charge transfer resistance of steel samples decreases in the order SIII> SII> SIconforming potentiodynamic polarization results. The corrosion rate increases and consequently thecharge transfer resistance decreases with increasing the immersion time for all steel specimens insodium chloride solution. This means that the presence of cement mortar around the steel bar decreasesthe contact of NaCl solution with metal which occurs through the pores in the cement mortar andhence the corrosion rate of steel decreases. In the presence of the superplasticizer within the cementmortar its porosity decreases and consequently decreases the passing of NaCl solution to steel surfaceresults in decreasing in its corrosion rate. Increasing of the superplasticizer concentration in cementmortar results in more decrease in the rate of steel corrosion in NaCl solution. Examining the steelsurface through scanning electron microscopy (SEM) indicated that this surface (SI)exhibits muchdamage more than that of steel in a mortar containing superplasticizer (SIII) when both exposed to thecorrosive sodium chloride solution.
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