In recent years, the anti-corrosive properties of natural extracts as environmentally friendly inhibitors have gained considerable interest. This study evaluates the potential of Marjoram (Origanum majorana L.) essential oil (OML), collected from Salé, Morocco, as a corrosion inhibitor for mild steel in 1 M HCl medium. The protection performance of OML was assessed using various electrochemical techniques, including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS), as well as the weight loss method. The influence of OML concentration and temperature on the inhibition performance were investigated. OML demonstrated pronounced inhibitory benefits via increasing the corrosion resistance of mild steel in the corrosive HCl solution, thus reducing the corrosion rate to 0.11 mg cm⁻² h⁻¹ and increasing the inhibition efficiency to 87.1% at an inhibitor concentration of 500 ppm. PDP confirmed that the inhibitor works as a mixed-type inhibitor with cathodic supremacy. EIS revealed that the charge transfer mechanism is the main controlling factor for the corrosion process. The thermodynamic parameters suggested a key role of OML physisorption in inhibition, following the Langmuir isotherm. Importantly, SEM and EDX analyses suggested the formation of a protective layer of the extract onto the steel surface, which shields the surface from corrosive species. This is owed to the functional group-rich phytochemicals of OML. Therefore, the development of bio-based corrosion inhibitors is not only a step towards more eco-friendly industrial practices, but also meets the growing demand for sustainable materials in a world with constrained resources.

Phytochemical-rich natural extracts have recently attracted intense attention as green corrosion inhibitors and costly benign coating components for the protection of metallic structures of immense commercial importance. Herein, various methods were applied to assess the corrosion protection efficiency of a methanolic extract of parsley (Petroselinum crispum) (PCE) on carbon steel C37 in 1 M HCl. Initially, the chemical profile of PCE was analyzed using gas chromatography/mass spectrometry (GC/MS), and myristicin and apiol were identified as the main components. The results from the weight loss, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) techniques revealed a substantial reduction in the corrosion rate upon the use of PCE, with a maximum inhibition efficiency of 92% at 1 g L⁻¹ PCE. To optimize the performance, the corrosion behavior was investigated over a temperature range of 303–333 K and for concentrations of 0.1–1 g L⁻¹. The inhibition effectiveness increased at higher concentrations of PCE, whilst it decreased when the temperature was elevated. The query suggests that the adsorption process involves both physical and chemical mechanisms. The adsorption of PCE onto C37 was well described by the Langmuir adsorption isotherm. The data were used to determine the activation energy and thermodynamic parameters. The PCE coating acted as a mixed-type inhibitor, hampering both cathodic and anodic corrosion reactions. SEM further confirmed the formation of a protective coating film on the steel surface when exposed to PCE. UV-Vis and XRD were implemented to understand the inhibition mechanism and formed products at the microscopic and spectroscopic levels. Hence, the green PCE inhibitor may potentially be applied in corrosion mitigation due to its high corrosion protection efficacy and its environmentally benign nature.

This study assessed the corrosion inhibitory and adsorption properties of two imidazol derivatives, namely 5-((2,4,5-triphenyl-1H-imidazol-1-yl)methyl)quinolin-8-ol (TIMQ) and 5-((2-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-1-yl)methyl)quinolin-8-ol (CDIQ), on carbon steel (CS) in 1 M of HCl using electrochemical methods, including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization measurements (PDP), UV–visible spectroscopy (UV–v), scanning electron microscopy (SEM), and molecular modeling. The findings showed that TIMQ and CDIQ were potent inhibitors with inhibition efficiencies of 94.8% and 95.8%, respectively. The potentiodynamic polarization experiments showed that the inhibitors worked as mixed-type inhibitors, and the impedance investigations supported the improvement of a protective layer for the inhibitor on the metal surface. Each inhibitor was adsorbed onto the carbon steel surfaces, according to the Langmuir adsorption method. The steel was shielded from acidic ions by an adsorbed coating of the inhibitor molecules, according to SEM. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations were used to inspect the results, and a good correlation was found between these results and those of the study. This information can be applied to determine the effectiveness of inhibitors in a HCl acid solution.

The novelty of the work is to scrutinize for the first time the 4R,5S- 2,4,5-tris(4-ethoxy­phenyl)-4,5-dihydro-1H-imidazole (TEPI) as a corrosion inhibitor for carbon steel (C35E) in the acidic medium. The inhibitory properties of TEPI were assessed through various methods, including electrochemical, spectroscopic, and surface analysis, as well as quantum chemical calculations. The protective effect of C35E was seen to expand as the TEPI amount was extended but to diminish as temperature was augmented, fulfilling 98.3 % at 1 mM under 303 K. Certain thermodynamic and kinetic indices were estimated and explored. The TEPI complied with the Langmuir adsorption isotherm when it adsorbs on the C35E surface. TEPI behaviour was revealed by polarization trials to be of mixed type. The establishment of an adsorption-linked preventive TEPI layer on the C35E surface has been disclosed thanks to surface analysis. The outcomes of scanning electron microscopy coupled with energy dispersive X-ray spectroscopy clearly illustrate that TEPI can effi­ci­ently adsorb at the C35E interface, substantially reducing C35E steel corrosion. UV-visible analysis of the inhibited electrolyte clearly reveals the complexation of iron cations with TEPI molecules. The density functional theory, Monte Carlo and molecular dynamic simulation were adopted to check out the adsorption characteristics of the TEPI onto C35E surface. The laboratory outcomes have been proven by DFT and MDS.

To decrease the environmental and health consequences associated with pollution, several cobalt oxides-decorated biochar substrates have been developed for effective catalytic reduction of 4-NP. The porous biochar was produced by pyrolysis of sewage sludge and acid demineralization, and subsequently, Co₃O₄ was loaded with varying amounts to synthesize Co₃O₄/biochar nanocomposites. The characterization of the materials included FTIR, XRD, SEM/EDX, TEM, BET, CHNS elemental analysis, TGA/DTA, and pH_pzc analysis. The catalytic activity of synthesized composites was monitored by UV-Vis spectroscopy to measure the transformation of a priority toxic pollutant, 4-NP, to a desirable pharmaceutical intermediate, 4-AP, by NaBH4, considering it a reducing agent. The influence of corresponding parameters such as catalyst dosage, NaBH₄ concentration, and Co₃O₄ content in the composite on the reduction time of 4-NP was modelled using central composite design (CCD) of RSM. The optimal conditions for the catalytic reduction of 0.3 mM 4-NP were found to be a catalyst dosage of 5 mg, a NaBH₄ concentration of 26 mM, and a Co₃O₄ loading of 13%, resulting in complete reduction within 5 min. The optimized catalyst displayed a high porosity, well dispersion of Co₃O₄ nanoparticles, good catalytic stability, and cost-effectiveness, revealing new insights into application of cobalt oxide and sewage sludge for pollutant reduction.

The long-term durability of reinforced concrete (RC) is critically threatened by chloride-induced corrosion of embedded steel reinforcement. While the influence of cement type on corrosion is widely recognized, the mechanistic relationship between cement chemistry and the electrochemical and microstructural evolution of steel–concrete interfaces (SCI) remains insufficiently resolved. Herein, we investigate how two commercially produced Portland cements (CA and CB) control the corrosion performance of reinforcing steel exposed to 3% NaCl solution. Electrochemical methods, including open circuit potential (OCP), polarization resistance, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP), were coupled with SEM and XRD to correlate corrosion kinetics with interfacial properties. Cement CA demonstrated superior corrosion performance, evidenced by a two-fold higher polarization resistance, lower corrosion current, and significantly enhanced charge-transfer resistance compared with CB, indicating the formation of a more stable passive layer. Combined electrochemical, SEM-EDX, and XRD results revealed a more protective steel–concrete interfacial environment in CA, with increased incorporation of O and Ca and formation of Fe oxides/hydroxides, suggesting intermixing of cement hydration products with the rust layer. These findings demonstrate that cement chemistry decisively influences alkaline reserve, passive film stability, and chloride-induced corrosion, providing mechanistic insights into steel–cement interfaces and guidance for designing durable cementitious materials.