Influence of sulfate salt type on passive film of steel in simulated concrete pore solution

Abstract

Abstract The durability of steel reinforced concrete caused by sulfate erosion is a big concern. However, little is known about the erosive effect of different types of sulfate salts on the properties of reinforced steel. This paper investigated the effects of four cationic sulfate salts (magnesium sulfate, ammonium sulfate, sodium sulfate, and calcium sulfate) on the stability of the passive film of reinforced steel in simulated concrete pore (SCP) solution. Open-circuit potential, Cyclic Polarization, Mott-Schottky and EIS electrochemical methods were employed to characterize the corrosion resistance of the passive film exposed to various sulfates. Moreover, the morphology of the steel was examined by optical microscope. The results showed that different types of sulfates exerted differing effects on the passive film of steel bar. Magnesium sulfate and ammonium sulfate seriously damaged the passive film of reinforced steel. Sodium sulfate was also harmful to the stability of the passive film. In contrast, calcium sulfate had a negligible influence on the passive film. At a given concentration, the samples immersed in magnesium sulfate and ammonium sulfate solutions possessed less corrosion resistance and a higher corrosion rate compared with those immersed in sodium chloride solution. Whereas, sodium sulfate imposed a weaker corrosion effect on the passive film. Findings from this study may provide new insights into the design and comparison of experimental studies on damages of reinforced concrete caused by different cationic types of sulfates.