Andres Carmona-Hernández

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.

Electrochemical potential noise signals from LiFePO₄ batteries often contain a slowly varying trend component that overlaps and distorts the intrinsic low-frequency electrochemical noise and must therefore be removed to enable reliable downstream analysis. To address this issue, this work presents a new segment-wise wavelet-based detrending (SWBD) method, applied to commercial rechargeable LiFePO₄/graphite batteries during discharge. The approach combines signal segmentation, dyadic discrete wavelet decomposition, and the joint optimal selection of the mother wavelet and decomposition level under a regularized SNR–RMSE–parsimony criterion, and it is validated against the most widely used detrending procedures: high-order polynomial fitting, empirical mode decomposition (EMD), and fixed wavelets. Quantitative evaluation across discharge segments shows that SWBD attains higher signal-to-trend ratios and lower reconstruction errors, ensuring improved temporal and spectral fidelity. According to the power spectral density (PSD) analysis, SWBD produces a smooth and continuous spectral slope with α ≈ 1, consistent with 1/f-type electrochemical noise. The Shannon energy analysis confirms a uniform and gradual multiscale energy distribution, reflecting efficient energy dispersion. Overall, the results demonstrate that SWBD provides a robust framework for adaptive trend removal, preserving the intrinsic stochastic dynamics of electrochemical fluctuations and enabling accurate spectral and statistical characterization in lithium-ion energy storage systems.

X65 steel is a very important material for the oil and gas industry, particularly for the construction of transportation and storage infrastructure, this is due to the excellent electromechanical properties of the alloy and relative low cost of acquisition. However, it is prone to corrosion in acid media, HCl for example, which is used during cleaning and maintenance. Expired drug Ardosons was studied as a potential corrosion inhibitor for X65 steel in acid media (1M HCl) at different temperatures (25 and 40 ºC). Open Circuit Potential (OCP) displacement towards more noble values, indicates the formation of a protective adsorbed layer on the metal surface, the magnitude of this shift allows the classification of Ardosons as a mixed corrosion inhibitor. Electrochemical evaluation was carried out by means of Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization Curves (PDP), the maximum observed efficiency at room temperature is 77.1% according to EIS and 60.3% according to PDP, while at 40 ºC, it is 51.6% according to EIS. A thermodynamic analysis reveals that the adsorption mechanism follows the Langmuir adsorption isotherm with a free Gibbs adsorption energy (ΔG°ads) of −19.06 kJ⸳mol−1 at room temperature and −8.50 kJ⸳mol−1 at 40 °C, both adsorption processes correspond to physisorption.

In this research work, the electrochemical evaluation of a non-ionic gemini surfactant as a green corrosion inhibitor for X100 pipeline steel in CO₂-saturated brine solution was carried out by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves (PPC). The corrosion inhibition performance of the gemini surfactant was studied in static and hydrodynamic conditions at room temperature and 60 °C. Electrochemical measurements showed that the inhibitor’s performance was enhanced with increasing inhibitor concentration and with increasing exposure time at room temperature, reaching the highest inhibition efficiency (η) at 100 ppm. With increasing temperature, the inhibitor efficiency decreased, with similar behavior at all concentrations. The analysis of the cathodic polarization curves at different rotation speeds showed the strong influence of mass transport on the cathodic process in the absence and the presence of the inhibitor. Under hydrodynamic conditions, PPC and EIS results indicated that the best inhibitor performance was with a concentration of 50 ppm, achieving a maximum inhibition efficiency of 91%. The adsorption of the inhibitor molecules on the surface obeyed the Langmuir isotherm, and the type of adsorption was mixed in all the study conditions. Surface characterization by scanning electron microscopy (SEM) revealed the formation of a protective corrosion inhibitor film.

In this research work, the influence of the electrolyte hydrodynamic conditions on the corrosion mechanism of the high-strength low-alloy (HSLA) X100 steel used in the petroleum transportation pipelines was analyzed. A Rotary Cylinder Electrode (RCE) was used to simulate the hydrodynamic conditions (1000 and 5000 rpm). Mechanical, microstructural and elemental characterization tests were performed on X100 steel, and the electrochemical impedance spectroscopy (EIS) technique was used to analyze the corrosion mechanism, while the morphology of the corrosion process on the corroded surfaces was obtained by scanning electronic microscopy (SEM). It was found that the increasing rotation rate (υ rot) generates a fully developed flow regime where the system was dominated by a mass transfer process and increases the kinetics of chemical and electrochemical reactions so there is an increase in the corrosion rate (CR). On the other hand, the adsorption of corrosion product films that limits the charge transfer process depended on the magnitude of the shear stress that can generate wear and roughness, as well as a greater number of anodic sites, leaving the metal exposure to the corrosive medium.

In this research, the Pistia stratiotes leaf (PSL) extract was evaluated as a green corrosion inhibitor for the corrosion of mild steel in 1 M HCl using electrochemical measurements and surface characterization. Electrochemical impedance spectroscopy (EIS) spectra showed that the inhibitory activity of the phytochemical compounds enhanced with increasing concentration up to 400 ppm, which was reflected in the increase in the charge transfer resistance and double-layer capacitance. Regarding the effect of immersion time, EIS results indicated that the persistence of the PSL extract was between 4 h and 8 h of exposure time. From polarization curve (PCC) results, the best performance of the corrosion inhibitor was achieved at 400 ppm with an inhibition efficiency of 93.7%. The PSL extract acted as a mixed-type corrosion inhibitor. The adsorption of the phytomolecules on the metal surface obeyed the Langmuir isotherm through a mixed mechanism (physical and chemical interactions) dominated by physisorption. Scanning electron microscopy (SEM) examinations and energy-dispersive X-ray spectroscopy (EDS) elemental analysis of the corroded samples confirmed the anticorrosive protection of the PSL extract. Chemical characterization of the PSL extract by GC-MS revealed the presence of phytol, steroids, and aromatic and long-chain unsaturated fatty acid esters, in order of abundance. Chemical quantum calculations by DFT allowed for determining that the phthalic acid, di(2-propylpentyl) ester compound has the most significant potential to act as the main active component in corrosion inhibition activity.

One of the alternative materials used for conducting conservation treatment of iron artifacts is the rust converter, since it generates barrier properties and more stable oxides. The protective properties and surface modifications from using Mimosa tenuiflora extract as a green rust converter on a gray iron oxide layer were studied. The surface characterization was carried out using a Scanning Electron Microscope coupled to an energy-dispersive X-ray spectrometer (SEM-EDS), along with infrared spectroscopy (IR), Raman spectroscopy, X-ray Diffraction (XRD), and Water Contact Angle (WCA). Electrochemical characterization was performed with an Electrochemical Impedance Spectroscope (EIS) using 3.5 wt.% NaCl as the electrolyte. According to the results of the Raman spectroscopy and XRD, the layer of corrosion products formed after 90 days in the atmosphere was composed of goethite, lepidocrocite, maghemite, hematite, and magnetite. The surface of the corrosion products was transformed with the rust converter into an amorphous and microcracked layer. By IR, the Fe-O and C-O-Fe bonds associated with the iron chelate were found with absorption bands at 1540 and 1567 cm⁻¹, respectively. By XRD, a modification of the magnetite crystallinity was observed. Finally, the Water Contact Angle and the protective capacity of the corrosion products were improved by the presence of the rust converter.