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. 2023 Sep 1;16(17):6017.
doi: 10.3390/ma16176017.

Corrosion of Reinforced A630-420H Steel in Direct Contact with NaCl Solution

Felipe M Galleguillos Madrid  1 , Alvaro Soliz  2 , Luis Cáceres  3 , Sebastian Salazar-Avalos  1 , Danny Guzmán  2 , Edelmira Gálvez  4
Affiliations

Corrosion of Reinforced A630-420H Steel in Direct Contact with NaCl Solution

Felipe M Galleguillos Madrid et al. Materials (Basel). .

Abstract

The deterioration of reinforced concrete structures in marine environments presents multiple problems due to the premature degradation of reinforced steel. 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. 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 is in concordance with the electrochemical results.

Keywords: A630-420H steel; mixed potential theory; oxygen reduction reaction; reinforced steel; saline solution.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Damaged buildings after 10 years in contact with the marine environment, Iquique, Chile. Corrosion damages on (a) retaining wall structures and (b) bottom of the bridge.
Figure 2
Figure 2
Electrode geometries for corrosion analysis made using 630A-420H steel: (a) rotating disc electrode for LSV measurements, (b) cylindrical electrode for WL measurements, and (c) bent electrode for LVS measurements under mechanical stress conditions.
Figure 3
Figure 3
Linear polarization curves for A630-420H steel in aerated sodium chloride solutions.
Figure 4
Figure 4
Deconstruction of polarization curves by applying mixed potential theory for A630-420H steel in contact with saline solutions: (a) 0.01 M NaCl, (b) 0.1 M NaCl, and (c) 0.5 M NaCl.
Figure 5
Figure 5
Linear polarization curves for A630-420H, A36, and AISI 1020 sheets of steel in 0.5 M NaCl solution under (a) aerated and (b) de-aerated conditions.
Figure 6
Figure 6
SEM images of A630-420H steel (a) before and (b–d) after corrosion process in aerated 0.5 M NaCl solution.
Figure 7
Figure 7
Linear polarization curves for A630-420H in contact with 0.5 M NaCl at OCP measured at different immersion times up to 288 h.
Figure 8
Figure 8
SEM images of corroded A630-420H steel after 288 h of immersion in 0.5 M NaCl solution with formation of (a–d) cracks and (e–h) pore sites.
Figure 9
Figure 9
SEM images of the corrosion products formed on the A630-420H steel surface after 288 h of immersion in 0.5 M NaCl solution, (a) magnification of 70,000×, (b) magnification of 20,000×, (c) magnification of 10,000×, and (d) elemental mapping of the corrosion products at magnification of 1999×.
Figure 10
Figure 10
XRD patterns for corrosion products after corrosion process of A630-420H samples immersed in 0.5 M NaCl solution during 288 h.
See this image and copyright information in PMC

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