Assessing the Corrosion Resistance of A630-420H Steel Exposed to NaCl Solution

The deterioration of reinforced concrete structures in marine environments presents multiple problems due to the premature degradation of reinforced steel. The corrosion of reinforcing steel exposed to seawater has received significant attention due to its widespread use in industrial and social infrastructures. This work aimed to study the corrosion of reinforced A630-420H steel when exposed to a 0.5 M NaCl solution. Although this carbon steel is the most widely used material for reinforced concrete structures in Chile, there is limited research on its resistance to corrosion when in contact with saline solutions. The electrochemical reactions and their roles in the corrosion rate were studied using linear sweep voltammetry, weight loss, scanning electron microscopy, and X-ray diffraction techniques. The experimental procedure was designed to examine the kinetics of the partial electrochemical reactions in A630-420H steel immersed in 0.5 M NaCl solution, with a focus on the hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and iron oxidation reaction (IOR). This analysis is unique as it used the superposition model based on mixed potential theory to determine the electrochemical and corrosion parameters. The outcomes of this study show that A630-420H steel has a higher corrosion rate than those of the other commercial carbon steels studied. This fact can be attributed to the competition between the cathodic oxygen reduction reaction and hydrogen evolution reaction, which also depends on the environmental conditions, exposure time, stabilization of the corrosion products layer, and presence of chloride ions. Additionally, the results under mechanical stress conditions show a brittle fracture of the corrosion product oriented longitudinally in the direction of the bend section, where the presence of pores and cracks were also observed. The corrosion products after corrosion were mainly composed of magnetite and lepidocrocite oxide phases, which are in concordance with the electrochemical results.