Mixed-type Inhibitor Research Articles

Corrosion inhibition effects of celery (Apium graveolens) seeds extract on carbon steel in acid medium

The present study highlights the inhibition performance of celery seeds (CS) extract on carbon steel immersed in 1M HCl, using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. This extract is selected due to biodegradable, renewable, and foremost aspect, is safe towards both the human being and environment. The studied inhibitor was easily extracted by using a simple aqueous extraction procedure. The experimental results show that the investigated inhibitor can effectively retard the corrosion process that occurs to carbon steel in hydrochloric acid solution. Electrochemical impedance spectroscopy (EIS) spectra showed that inhibition efficiency increases with the increasing of (CS) extract concentration. Among the studied inhibitor showed maximum inhibition efficiency of 96,86% at 250 ppm. Polarization curves indicate that (CS) extract acted as mixed type of inhibitors with a predominant effect on the anodic reactions. Basic calculations for the adsorption studies were also carried out. The adsorption of the extract onto carbon steel surface followed the Langmuir adsorption isotherm.

Eco-friendly corrosion inhibition of steel using phenolic compounds from Cynara syriaca

This study evaluates the corrosion inhibition performance of the n-butanol (n-BuOH) fraction derived from Cynara syriaca on mild steel in acidic environments. The n-BuOH fraction achieved up to 94 % inhibition at 500 ppm, as assessed through gravimetric analysis, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). Key phenolic compounds, including kaempferol, naringenin, myricetin, chlorogenic acid, and quercetin, were identified by UPLC-MS/MS. These compounds form stable flavonoid-metal complexes, as confirmed by UV–Vis spectroscopy. FT-IR and SEM-EDS analyses revealed the formation of protective coatings and interactions with the steel surface. Polarization curves indicate that the n-BuOH fraction acts as a mixed-type inhibitor, predominantly affecting the anodic reaction. The inhibition efficiency decreased from 93.89 % to 73.43 % with increasing temperatures. Thermodynamic analysis showed an increase in activation energy (Ea = 58.20 kJ/ mol) and a positive ΔH value of 56.17 kJ/mol, which can be attributed to the increased thickness of the double layer, enhancing the activation energy of the corrosion process. A Gibbs free energy (ΔG0ads) value of −25.48 kJ/mol confirms that the adsorption process is spontaneous and involves both physisorption and chemisorption. pKa analysis identified specific adsorption sites. This research underscores the potential of the n-BuOH fraction as a novel, eco-friendly corrosion inhibitor, offering valuable insights for sustainable corrosion control strategies.

Synthesis investigation and exploring of new tetraglycidyl bisurea bisphenyl S polyepoxide as an excellent corrosion inhibitory resin for mild steel in 1M HCl environment: Comprehensive approaches

This work reports the synthesis of new epoxy resin namely tetraglycidyl bisurea bisphenyl S (TGBUBS). TGBUBS was characterized through using nuclear magnetic resonance (1H NMR and 13C NMR) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). TGBUBS was investigated as an excellent organic inhibitor for protecting the mild steel from corrosion in 1M HCl solution at different concentrations. Anticorrosion protection behaviors were evaluated and more discussed including different techniques such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and contact angle (CA) measurements. The obtained results showed that the TGBUBS exhibited inhibition efficiencies at lower concentration are 93.19 % (PDP) and 91.21 % (EIS), respectively. Further, PDP measurements indicated that the TGBUBS acted as a mixed-type inhibitor in 1M HCl solution. Furthermore, SEM and EDS analysis showed a significant reduction in the corrosion on the mild steel surface when the inhibitory epoxy resin was present compared to the blank solution (1M HCl). The effectiveness and interactions of the new epoxy resin on the mild steel surface were also predicted using DFT calculations and molecular dynamics (MD) simulations. The theoretical approaches are in agreement with the experiment results.

Chemical Variation and Biological Properties of the Essential Oil and Main Volatiles of Pimenta dioica Harvested in the Northern Highlands of Puebla, Mexico.

The chemical variation of the annual essential oils from Pimenta dioca (PdEOs) grown in the Northern Highlands of Puebla, Mexico, and their biological activities were determined. Eugenol (>50%) and beta-myrcene (>16%) were the main volatiles contained in the annual PdEOs (2022-2024) extracted from fruit and leaves. PdEOs showed inhibitory properties on human pancreatic lipase (IC50, 33-44 µg/mL) through mixed type inhibition with clear eugenol involvement (IC50, 47 µg/mL). The oral administration of PdEOs and eugenol combined with corn oil on ICR mice (p < 0.01), confirmed a strong anti-hypertriglyceridemic activity at 3 and 4.5 h post-treatment. PdEOs showed low toxicity in 3T3 fibroblasts and probiotics (IC50 >500 µg/mL), whereas high lethal dose in ICR mice (LD50 >8000 mg/kg BW). Eugenol, beta-myrcene and PdEOs decreased Helicobacter pylori viability acting as mixed inhibitors on urease. Results of anti-lipase and anti-H.pylori urease assays were endorsed by docking calculations.

Synthesis and biological evaluation of esculetin derivatives as antidiabetic agents

Esculetin derivatives 4a-4j (including six novel hydroxylated/halogenated derivatives 4a, 4d, 4e, 4f, 4g, 4h) were synthesized through Perkin reaction with 2,4,5-trihydroxybenzaldehyde and appropriate phenylacetic acid as raw materials, and screened for α-glucosidase and α-amylase inhibitory activities. Among these compounds, compound 3-(3-iodophenyl)-6,7-dihydroxy-2H-chromen-2-one (4d) showed promising hypoglycaemic activity with half maximal inhibitory concentration (IC50) values of 0.18±0.03 mM and 1.82±0.18 mM against α-glucosidase and α-amylase, respectively, classifying it as a mixed-type inhibitor. Compound 4d could statically quench the intrinsic fluorescence of enzymes, which bound to enzymes mainly through hydrogen bonding and hydrophobic interactions affecting the microenvironment of proteins. Compound 4d also exhibited antioxidant activity, which demonstrated good scavenging effects for 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals. Furthermore, compound 4d still maintained a certain degree of hypoglycemic and antioxidant activities after simulated gastrointestinal digestion. The oral toxicity study showed that compound 4d had no significant effect on the serum biochemical indices and organs of mice, indicating its safety profile. This study suggests that esculetin may be a potential skeleton to the development of hypoglycaemic drugs.

Electrochemical study and modeling of an innovative pyrazole carboxamide derivative as an inhibitor for carbon steel corrosion in acidic environment.

The impact of N,1-dibenzyl-5-methyl-1H-pyrazol-3-carboxamide (BPC) on the carbon steel (CS) corrosion in hydrochloric acid (1M) was studied in this work, considering concentration and temperature effects. Electrochemical investigation indicated that BPC functions as a mixed-type inhibitor. For an optimal BPC concentration of 125ppm, the inhibition efficiency of 91.55% was obtained at 298K. According to adsorption isotherm of Langmuir, the BPC adheres to the CS with standard adsorption free energy (ΔG°ads) of - 26.76kJmol-1. Furthermore, the calculation of dissolution activation parameters revealed an increase in energy (Ea) from 46.48 to 94.97kJmol-1, an elevation in the enthalpy (∆Ha) from 43.89 to 92.37kJmol-1, and a rise in the entropy (∆Sa) from - 91.17 to 51.43Jmol-1K-1 in the presence of 125ppm of BPC. The experimental results were confirmed by quantum chemistry calculations based on density functional theory (DFT) and molecular simulations using the Monte Carlo method. These theoretical approaches also allowed for a comparison of the inhibitory performances of BPC with its protonated form, BPCH, the latter being found more effective. Moreover, the study of the radial distribution function g(r) predicted that the nature of the bond formed with the steel surface is of a chemical type.

2-Amino-6-methylbenzothiazole as corrosion inhibitor for low carbon steel in acidic solution: Experimental and theoretical studies

The corrosion susceptibility of S235 steel samples in 1 M HCl solution, with and without addition of 2-amino-6-methylbenzothiazole (AMBT) was evaluated using weight loss (WL), chronopotentiometry, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PD) techniques. The corrosion inhibition efficiency of AMBT was investigated at 298 to 318 K, with and without addition of 0.5 wt% KI. The highest corrosion inhibition efficiency (i.e. 83.30 %) was achieved upon addition of 5 mM AMBT. PD curve measurements after 24 h immersion revealed that AMBT behaves as a mixed-type inhibitor, predominantly affecting the cathodic corrosion reaction. Thermodynamic calculations showed that AMBT adheres to the Langmuir adsorption isotherm. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) was used to confirm the adsorption of AMBT, while its influence on the morphology of the S235 steel samples was also investigated by scanning electron microscopy (SEM). Density Functional Theory (DFT) calculations, along with Monte Carlo (MC) and Molecular Dynamics (MD) simulations, were employed to investigate AMBT’s corrosion inhibition behaviour at the molecular level. The simulations confirmed that AMBT strongly adsorbs on the Fe(110) surface through a combination of physisorption and chemisorption mechanisms. This study offers detailed insights into AMBT’s effectiveness as a corrosion inhibitor

Novel eco-friendly quinolinone derivative as a water-soluble corrosion inhibitor for low carbon steel: Synthesis, inhibitive efficacy, and DFT analysis

A novel and rapid synthetic route for producing 4-imino-3-(2-phenylhydrazono)-3,4-dihydroquinolin-2(1H)-one (IQ) from 3-(2-phenylhydrazono)quinoline-2,4(1H,3H)‑dione 1 is introduced. The inhibitory effectiveness of IQ in mitigating the corrosion of low carbon steel (LCS) in acidic environments was evaluated using weight loss (Wt-L) and electrochemical methods, such as potentiodynamic polarization (Pd-P) and electrochemical impedance spectroscopy (EIS). The optimum concentration of IQ was determined to be 30×10−3 Mm, at which it exhibited the highest inhibition efficiency of approximately 93.2 %. The nature of IQ as a mixed-type inhibitor was demonstrated by its ability to inhibit both anodic and cathodic reactions, primarily acting as an anodic inhibitor.The adsorption of IQ onto the LCS surface followed the Langmuir adsorption model, indicating a monolayer adsorption mechanism. Moreover, EIS findings suggest that IQ forms a protective layer on the LCS surface at the metal/electrolyte interface, preventing its dissolution in the acidic medium. Further analysis of the corrosive solution containing IQ after two days of LCS immersion showed the formation of Fe-IQ complex, confirmed by ultraviolet/visible spectroscopy. Using atomic force microscopy (AFM), we confirmed that a protective layer of IQ forms on the surface of LCS. Additionally, in silico studies of IQ revealed the active sites responsible for its interaction with the LCS surface under acidic conditions. These findings underscore the potential of IQ as an effective corrosion inhibitor for LCS in acidic environments, providing significant protection by forming a stable, protective film on the metal surface.

Electrochemical and quantum chemical investigation on the adsorption behavior of a schiff base and its metal complex for corrosion protection of mild steel in 15 wt% HCl solution

This work evaluates the effectiveness of Schiff base derivatives, namely, 2,2'-((1E,1′E)-((2,2-dimethylpropane-1,3-diyl)bis(azaneylylidene))bis(methaneylylidene))diphenol (DAMD) and (2-((E)-((3-(((E)-2-hydroxybenzylidene)amino)-2,2dimethylpropyl)imino)methyl)phenoxy) zinc (HDMZ), as corrosion inhibitors for mild steel in a 15 % HCl solution. By employing a blend of experimental assessments and theoretical computations, such as electrochemical tests, morphological observations, and theoretical simulations, the study achieved an impressive up to 94.6 % inhibition efficiency. Notably, HDMZ exhibited significant protective properties. The results of PDP showed that both inhibitors act as mixed-type corrosion inhibitors. SEM surface analysis of the uninhibited and inhibited samples revealed the formation of a protective layer of inhibitor molecules on the mild steel surface to mitigate its corrosion. The Langmuir adsorption model verified the occurrence of dual adsorption, while theoretical simulations offered insights into the underlying interaction mechanisms. The identification of Schiff-based inhibitors reveals a pronounced synergistic effect in corrosion inhibition, marking a significant advancement in understanding corrosion control mechanisms. This study illuminates the process of forming covalent bonds between inhibitor molecules and iron atoms, presenting a hopeful path towards the advancement of corrosion inhibitors tailored for industrial use. The parallel adsorption configuration and mutual interactions form a stable structure, reinforcing the organic-metal bonds and enhancing both chemical and physical adhesion to the steel surface. These findings indicate that the synergistic effect of molecular interactions and polar-rich regions offers a promising strategy for designing functional hybrid materials.

Trypsin from digestive tract of harpiosquillid mantis shrimp: Molecular characteristics and the inhibition by chitooligosaccharide and its catechin conjugate.

Trypsin from the digestive tract of harpiosquillid mantis shrimp (HMS) was purified using ammonium sulfate precipitation and a soybean trypsin inhibitor-CNBr-activated Sepharose 4B affinity column. The purified trypsin (PTRP-HMS) had a purity of 30.4-fold, and a yield of 14.5% was obtained. PTRP-HMS had the molecular weight of 23.0kDa as examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and only one isoform was detected by native-PAGE. Its optimal temperature and pH were 55°C and 8.5, respectively. TLCK almost completely inhibited the activity of trypsin. The PTRP-HMS had a Michaelis-Menten constant (Km) and catalytic constant (Kcat) of 0.87mM and 13.04s-1, respectively, toward Nα-benzoyl-l-arginine 4-nitroanilide hydrochloride. When chitooligosaccharide (COS) and COS-catechin (COS-CAT) conjugates were examined for inhibition toward the PTRP, the latter exhibited higher efficacy in inhibiting the trypsin. Both COS and COS-CAT conjugate showed mixed-type inhibition kinetics. As a consequence, COS and COS-CAT conjugate could be used as natural additives for inhibiting trypsin in whole HMS, thus retarding the softening and lengthening the shelf-life of HMS during the iced storage. PRACTICAL APPLICATION: Harpiosquillid mantis shrimp (HMS) is of high demand due to its delicacy. However, its meat undergoes rapid softening within 2-3 days when stored in ice. Understanding causative proteolytic enzymes, especially trypsin from digestive tract, paves a way for preventing their negative impact on HMS eating quality. Employment of safe inhibitors, for example, chitooligosaccharide (COS) or COS conjugated with catechin, could inhibit HMS trypsin. Overall, softening of whole HMS containing trypsin in its digestive tract can be impeded, especially when treated with COS-CAT. This finding is beneficial for the HMS local vendor or exporter, in which HMS quality can be maintained.

Experimental and computational investigations on the synergistic inhibition mechanism of biphenyl quinoline quaternary ammonium and hexamethylenetetramine on the corrosion of J55 steel in 20 wt% HCl solution

The present study involves the synthesis of a novel biphenyl quinoline quaternary ammonium salt (BDQ) and its application in combination with hexamethylenetetramine (HMT) as a compounded corrosion inhibitor for acid stimulation, aiming to effectively prevent the corrosion of J55 steel in a 20 wt% HCl solution at 60 °C. The optimized BDQ/HMT mixture (with a mass ratio of 1:3) at 0.4 wt% produced a significant decrease in the corrosion rate of J55 steel to 3.7637 g/(m2·h), much lower than the requirement of 5.0 g/(m2·h) stipulated by the standard SY/T 5404–2019. The electrochemical analysis demonstrated that the BDQ/HMT mixture exhibited a mixed-type corrosion inhibitor with predominantly anodic characteristics, retarding both the anodic oxidation and cathodic reduction reactions of J55 steel in the HCl solution. The adsorption studies revealed that BDQ conformed to a Langmuir-type adsorption isotherm on J55 surfaces, driven by a combination of physisorption and chemical interactions, with chemical interactions playing a dominant role. Additionally, quantum chemical calculations and molecular dynamics simulation were also performed to elucidate the observed synergistic effect of BDQ and HMT.

Revitalizing sumatriptan: transforming expired medication into a potent solution for corrosion control in acidic environments

The concerns regarding pharmaceutical waste, particularly expired drugs have prompted the exploration of their alternative applications. This research highlights the potential of repurposing expired pharmaceuticals as eco-friendly corrosion inhibitors for their industrial applications. An expired drug sumatriptan was investigated for its anticorrosive properties on MS in 1 M HCl medium. Electrochemical techniques, including potentiodynamic polarization and electrochemical impedance spectroscopy, were employed to evaluate the inhibition efficiency and complemented by surface characterization studies (SEM, EDAX, CA and AFM). The results demonstrated that sumatriptan acts as an effective mixed-type inhibitor, achieving maximum inhibition efficiencies of 94.51% and 93.85% from PDP and EIS studies respectively for 500 ppm at 318 K. The adsorption of sumatriptan on the metal surface followed the Langmuir isotherm having an R2 value of ∼1, suggesting a physical adsorption behaviour with Δ G° values ranging from −16.286 to −21.518 kJ mol−1. The results demonstrate the effectiveness of sumatriptan as a corrosion inhibitor and the potential of repurposing expired pharmaceuticals as eco-friendly and sustainable alternatives.

The novel mechanism on the inhibition of superoxide anion generating from xanthine oxidase in the presence of myricetin

To gain an in-depth understanding of the process of myricetin (MY) inhibiting the generation of •O2− from Xanthine Oxidase (XOD) at a novel perspective, the inhibiting pathway is necessary to be re-elaborated through inhibitory type, thermodynamic analysis and molecular simulation. The results demonstrated that MY is indeed a potent inhibiting agent for •O2− producing from XOD, with the maximum value of 33.78 % in the inhibition of •O2−. Furthermore, the deprotonated form (De-MY) of MY was examined to be an effective agent for interacting with XOD, with the measurement of •O2− in productions from MY, XOD@MY and XAN-XOD@MY, as comparing to the XAN-XOD@ALL. On the inhibition kinetics, De-MY was witnessed to be on a mixed-type inhibition, with more competitive inhibition. In the thermodynamic analysis, the Stern-Volmer plots for De-MY obtained at 298 K, 303 K and 308 K, were polynomial-fitted to form curves approaching the X axis via the fluorescence quenching of XOD, which was against the reported with good linearity. It indicated that the interaction between De-MY and XOD occurred at the range of MY concentrations from 0 to 0.025 (×10−5 mol L−1), is dominated by a static quenching procedure, ascribing to the appearance of accessible interaction with corresponding f values less than 1. As well, via combining the synchronous fluorescence data, Molecular dynamics simulations showed that MY binding to the Trp 283, ARG-60 and Tyr 58 with H-binding interactions is an available access to block the transfer of free electrons from FADH2 to O2. Therefore, in this work, successfully re-elaborating the inhibition mechanism of •O2− generating from XOD by MY is benefited for MY in the future applications.

Evaluation of cactus mucilage as a green corrosion inhibitor for copper in sulfuric acid environment

This study investigates the corrosion inhibition performance of cactus mucilage for copper in 0.5 M H2SO4 solution. The cactus mucilage was extracted using a pure water extraction method and characterized using FTIR and GC-MS analyses. The inhibition efficiency was evaluated using potentiodynamic polarization and EIS techniques, while surface morphology was analyzed using SEM and AFM. The potentiodynamic polarization results revealed that cactus mucilage acts as a mixed-type inhibitor, with inhibition efficiency increasing from 78.6% at 100 mg L-1 to 94.5% at 600 mg L-1. The EIS measurements showed a significant increase in charge transfer resistance from 0.56 k? cm-2 in the uninhibited solution to 8.26 k? cm-2 with 600 mg L-1 cactus mucilage. The adsorption of cactus mucilage on the copper surface followed the Langmuir isotherm model, with a strong adsorption equilibrium constant of 23.6 × 103 M. Compared to other green inhibitors, cactus mucilage exhibited superior inhibition efficiency and sustainability advantages, making it a promising eco-friendly alternative for copper corrosion protection.

Design, synthesis, biological evaluation, and molecular modeling studies of some quinazolin-4(3H)-one-benzenesulfonamide hybrids as potential α-glucosidase inhibitors

Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycemia, posing serious health risks and becoming increasingly prevalent. Prolonged hyperglycemia can lead to complications such as nephropathy, neuropathy, retinopathy, cardiovascular damage, and blindness. Controlling hyperglycemia through α-glucosidase inhibitors, which slow down carbohydrate breakdown, is an effective treatment strategy. However, current inhibitors like acarbose, voglibose, and miglitol while used to manage type 2 diabetes, have significant side effects. Therefore, developing new α-glucosidase inhibitors that are more effective and have fewer side effects is crucial. In this study, a series of novel quinazolin-4(3H)-one-benzenesulfonamide hybrid compounds were designed, synthesized, and evaluated for in vitro α-glucosidase inhibitory activity. The compounds showed higher enzyme inhibition potency, with IC50 values ranging between 129.2 ± 0.5 and 558.7 ± 13.7 µM, compared to acarbose (IC50=814.3 ± 13.5 µM). Among the tested compounds, compound 10, bearing a 4-chlorophenyl ring on the nitrogen atom of the sulfonamide group, was the most active, with an IC50 value of 129.2 ± 0.5 µM. Enzyme kinetics analyses and molecular modeling studies were conducted to understand their inhibition mechanisms and interactions with the enzyme. The kinetic studies revealed a mixed-type inhibition model, indicating that the compounds bind to the enzyme-substrate complex with higher affinity than to the free enzyme. Molecular modeling results confirmed these findings. Additionally, in silico prediction studies showed that the selected compounds have favourable physicochemical and drug-like properties. These results suggest these compounds have potential for further optimization and development as effective α-glucosidase inhibitors for diabetes treatment.

Comparative insights into the inhibition of pancreatic lipase by quercetin using Mg-MOF-74 as nano-carrier: Inhibitory interaction, inhibition activity and conformational change

As one of the focus causes of death in the world, obesity has attracted much attention in recent years. Pancreatic lipase (PL), an outstanding target for obesity, is an enzyme which can decompose dietary lipids. Based on the good performance and drug loading effect of Mg-MOF-74, the interaction mechanism and inhibition mechanism of quercetin (Que) loaded with Mg-MOF-74 on PL were studied by multispectral technology and enzyme inhibition kinetic analysis. The effect of Mg-MOF-74 loaded Que on PL is a mix quenching process dominated by hydrophobic force. Fluorescence spectral data of the nanocomposite system were resolved by multivariate curve resolution-alternating least squares. The complex system equilibrated at a [Que]:[PL] ratio nearly 2. The conformation of PL changes under the influence of Mg-MOF-74 and Mg-MOF-74-Que were demonstrated through 3D fluorescence, Fourier transform infrared spectroscopy and circular dichroism spectrum. Molecular docking studies showed that more hydrogen bonds were formed and confirmed the stronger binding affinity of PL when Que loaded on Mg-MOF-74 (−103.17 kcal mol−1). Further analysis of the inhibition kinetics showed that PL-Que belonged to the mixed inhibition type, PL-Mg-MOF-74-Que belonged to the non-competitive inhibition type, and the inhibition constants were Ki, Que (16.63 ± 7.49 × 10−6 mol L−1) > Ki, Mg-MOF-74-Que (10.68 ± 2.04 × 10−6 mol L−1). Through investigating the inhibitory mechanism and interaction between Mg-MOF-74-Que and PL on a molecular level, it affords a new idea for the design of new PL inhibitors and a new method for the potential treatment of obesity.

Assessment of three quinolin-8-ol-imidazole hybrids as corrosion carbon steel inhibitors in acidic conditions employing practical and theoretical methodologies

Three hybrids of quinolin-8-ol-imidazole were scrutinized as corrosion inhibitors in 1 M HCl for carbon steel (Cstl). These hybrids are 5-((2-(4-(dimethylamino)phenyl)-4,5-diphenyl-1H-imidazol-1-yl)methyl)quinoline-8-ol (Quin-Amino), 5-((4,5-diphenyl-2-(p-tolyl)-1H-imidazol-1-yl)methyl)quinoline-8-ol (Quin-Tolyl), and 5-((2-(4-bromophenyl)-4,5-diphenyl-1H-imidazol-1-yl)methyl)quinoline-8-ol (Quin-Br). The current research includes a mixture of methods. In addition to computational approaches, several experimental approaches were employed, such as electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM-EDX), UV–vis spectroscopy, and potentiodynamic polarization (PDP). The investigated hybrids' corrosion resistance was encountered to be concerned by the concentration, temperature, and chemical structure, which attained a maximum of 96.1 % for Quin-Amino, 93.4 % for Quin-Tolyl, and 92.5 % for Quin-Br at 10−3 M, respectively. The PDP results illustrated that the studied hybrids performed as mixed-type inhibitors. In addition, the chemisorption of these hybrids on the Cstl surface obeyed the Langmuir adsorption isotherm. SEM-EDX confirmed that the effectiveness of the three hybrids lies in their capability to develop an organic layer on the Cstl surface. The density functional theory (DFT) was employed for theoretical calculations. Molecular dynamics (MD) simulations manifest that hybrids are oriented beneficially on the Fe (110) surface, providing a high surface coverage and thus a high inhibition performance.

Insight into the Corrosion Inhibition Performance of Pistia stratiotes Leaf Extract as a Novel Eco-Friendly Corrosion Inhibitor for Mild Steel in 1 M HCl Solution.

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.

Insights into the corrosion inhibition performance of essential oil of Teucrium luteum subsp. flavovirens for carbon steel in 1.0 M HCl medium: experimental and theoretical evaluations

The objective of this research work was to assess Teucrium luteum subsp. flavovirens essential oil (EOTL), for the first time, as novel and eco-friendly corrosion inhibitor for carbon steel (CS) in 1.0 M HCl medium. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and surface analysis were employed to assess the effectiveness of the EOTL. The findings indicate that the EOTL reduces the corrosion of CS in hydrochloric acid and offered an inhibition efficiency (IE) of 91% at a dosage of 2.00 g/L at 298 K. The PDP data showed that EOTL behaved as a mixed-type corrosion inhibitor. The effect of immersion time and temperature on the corrosion inhibition performance of EOTL was also studied. It was found that the IE increased only up to 24 h and decreased with prolonged immersion time. In addition, the IE diminished with increasing temperature. The EOTL molecules adsorbed on the CS surface following Langmuir adsorption isotherm, with an adsorption energy ranging from −16 to −27 kJ/mol, an indication of physico-chemical adsorption mechanisms. The SEM/EDX results provide evidence of the presence of a protective film of the inhibitor on the surface of the CS. Theoretical studies using DFT, Monte Carlo simulations, molecular dynamics simulations and mean square displacement were conducted to given insight into the contributions of the four main components of EOTL. This work not only introduces a sustainable alternative to conventional corrosion inhibitors but also provides a robust understanding of the underlying mechanisms, hence contributing to advancement in corrosion science.

Evaluation of thiocarbohydrazide derivative as corrosion inhibitor for C1018 carbon steel in 3.5% NaCl + 500ppm HAc solution: Electrochemical, SEM, FTIR and computational studies

N'-((E)-3-phenylallylidene)hydrazinethiocarbohydrazide (PHCT) was synthesized, purified, characterized and assessed for its inhibitive property against the sweet corrosion of C1018 carbon steel in CO2-saturated 3.5 % NaCl + 500 ppm HAc solution at 25 and 60 °C. At 50 ppm and 25 °C, electrochemical impedance spectroscopy (EIS) confirmed that the presence of PHCT in the electric double layer fortified the hydrophobicity of the region and mitigated rate of charge transfer. Potentiodynamic polarization (PP) measurements at 25 °C showed that PHCT is a mixed-type inhibitor, which could reduce corrosion rate from 24.32 mpy in blank to 0.67 mpy at 50 ppm dosage and deliver 97.24 % inhibition efficiency. PHCT adsorbs, principally, using its NH2, C = S and C = C functional groups, based on FTIR characterization. Computational modeling using the FMO and MEP analyses confirmed that PHCT exhibits higher electron donating than electron accepting power and interacts with the metal surface through nitrogen and sulfur atoms. Scanning electron microscopy (SEM) confirmed the ability of PHCT to protect the steel surface from localized pitting corrosion. Although increasing the temperature up to 60 °C diminished the efficiency of PHCT, the inhibitor was able to provide up to 92 % efficiency.