Evaluation of the Corrosion Mechanism of Reinforced Concrete with Surface Treatment of Silica Nanoparticles by Electrochemical Noise Analysis

This research evaluated the electrochemical effects of using SiO2 nanoparticles (NPs) as a surface treatment to reduce porosity in steel–concrete systems exposed to synthetic seawater. Corrosion behavior of steel rebars was investigated using electrochemical noise (EN) measurements, employing several EN analysis methods, including shot noise, Discrete Wavelet transform (DWT), and Hilbert–Huang transform (HHT). SiO2 NPs were synthesized from sugarcane bagasse ash and incorporated into concrete systems fabricated with Type 40 composite Portland cement and embedded AISI 1018 carbon steel. The treated systems (designated NP) were subjected to cyclic wetting–drying exposure in synthetic seawater. EN analysis revealed that the reference system (R) exhibited a metastable localized corrosion process. In contrast, the incorporation of NPs modified the microstructure and porosity of the cementitious matrix, thereby modifying the electrochemical response of steel rebars. Shot noise analysis showed corrosion events with lower charge but higher repetition rates, suggesting an increase in the frequency of metastable corrosion processes. Furthermore, DWT and HHT analyses detected periods of increased energy release. This behavior was attributed to a transient stage of a localized process involving partial depassivation, passive film breakdown, and subsequent repassivation. At the end of the exposure period, both systems exhibited partial repassivation, indicating partial recovery of their protective passive conditions.