Experimental and theoretical studies of benzalkonium chloride as an inhibitor for carbon steel corrosion in sulfuric acid

In situ study of the interactions between metal surfaces and cationic surfactant corrosion inhibitors by surface-enhanced Raman spectroscopy coupled with visible spectroscopy

Cationic surfactants are widely used as corrosion inhibitors for industrial tubings and pipelines. They protect the surface of steel pipes through a film-forming mechanism, providing both anodic and cathodic inhibition. To improve the efficiency of the corrosion protection, it is essential to understand the interactions between the surfactants and metal surfaces. To achieve this, surface enhanced Raman spectroscopy (SERS) can serve as a powerful tool due to its surface sensitivity and potential to detect trace amounts of analytes in complex media. In this contribution, we have investigated the behaviour of in situ prepared AgNPs in the presence of benzalkonium chloride as a model corrosion inhibitor using SERS coupled to visible spectroscopy and combined with light scattering methods. By combining these experimental methods, we were able to correlate the aggregation of silver particles with the concentration of added surfactant in the resulting mixture. Using this insight, we also established a SERS method for the detection of benzalkonium chloride traces in water. For this, we utilised the quenching of the SERS response of methylene blue by competitive adsorption of methylene blue and the surfactant on SERS active AgNPs. We believe that our approach can serve a variety of applications to improve the industrial water treatment. For example, the modelling of the interaction of different surfactants with SERS can be used for process intensification, and ultimately, to move towards the digital twinning of corrosion processes for more efficient corrosion inhibition. Furthermore, the ability to adapt our sensing protocol for on-line corrosion inhibitor monitoring allows a fast response to process changes, hence, enabling resource-efficient, continuous process control.

Synergistic inhibition effect of ultraviolet irradiation and benzalkonium chloride on the corrosion of 316L stainless steel caused by Aspergillus terreus

Microbiologically influenced corrosion (MIC) is a key factor that damages engineering materials in marine environments. One of the major concerns in this regard is the corrosion protection of stainless steel (SS) caused against fungal attacks. This study investigated the effect of ultraviolet (UV) irradiation and benzalkonium chloride (BKC) on the corrosion of 316L stainless steel (316L SS) induced by marine Aspergillus terreus in 3.5 wt% NaCl solution. This was accomplished by employing microstructural characterisations and electrochemical analysis to analyse the synergistic inhibition behaviour of the two methods. The results indicated that while UV and BKC demonstrated individual abilities to suppress the biological activity of A. terreus, their inhibitory effects were not significant. The combination of UV light and BKC was found to cause a further decline in the biological activity of A. terreus. The analysis revealed that the combination of BKC and UV significantly decreased the sessile cell counts of A. terreus by more than three orders of magnitude. The fungal corrosion inhibition effect of individual application of UV light or BKC did not yield satisfactory results owing to the low intensity of UV and low concentration of BKC. Furthermore, the corrosion inhibition of UV and BKC occurred mainly during the early stages. The corrosion rate of the 316L SS declined rapidly when the combination of UV light and BKC were used, indicating that UV light and BKC exert a good synergistic inhibitory effect on the corrosion of the 316L SS caused by A. terreus. Therefore, the results suggest that the combination of UV light and BKC can be an effective approach to control the MIC of 316L SS in marine environments.

Evaluation of inhibitive corrosion potential of symmetrical hydrazine derivatives containing nitrophenyl moiety in 1M HCl for C38 steel: experimental and theoretical studies

The exploitation of cost-effective, sustainable, green and efficient compounds is a renewed science and a demanding mission for today's chemists and technologists. In this view, the inhibitive corrosion properties of some hydrazine derivatives named (1E,2E)-bis(1-(2-nitrophenyl)ethylidene)hydrazine (SSBO), (1E,2E)-bis(1-(3-nitrophenyl)ethylidene)hydrazine (SSBM) and (1E,2E)-bis(1-(4-nitrophenyl)ethylidene)hydrazine (SSBP) on the C38 steel corrosion in 1M HCl media has been evaluated by different techniques like electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. The EIS results showed that SSBM is the greatest inhibitor (η>93%) among the three tested compounds. The SSBM gives considerable inhibition efficiency against corrosion of steel compared to the previous studies. The PDP curves indicated that the studied inhibitors were a mixed-type inhibitor with a predominantly cathodic control. Quantum calculations of some descriptors derived from the density functional theory (DFT), the transition state theory (TST), the quantum theory of atoms in molecules (QTAIM) and molecular dynamics simulation have delivered helpful information regarding electron transfer and mechanism during adsorption of inhibitors on C38 steel surface.

Molecular modelling of compounds used for corrosion inhibition studies: a review

Molecular modelling of organic compounds using computational software has emerged as a powerful approach for theoretical determination of the corrosion inhibition potential of organic compounds. Some of the common techniques involved in the theoretical studies of corrosion inhibition potential and mechanisms include density functional theory (DFT), molecular dynamics (MD) and Monte Carlo (MC) simulations, and artificial neural network (ANN) and quantitative structure-activity relationship (QSAR) modeling. Using computational modelling, the chemical reactivity and corrosion inhibition activities of organic compounds can be explained. The modelling can be regarded as a time-saving and eco-friendly approach for screening organic compounds for corrosion inhibition potential before their wet laboratory synthesis would be carried out. Another advantage of computational modelling is that molecular sites responsible for interactions with metallic surfaces (active sites or adsorption sites) and the orientation of organic compounds can be easily predicted. Using different theoretical descriptors/parameters, the inhibition effectiveness and nature of the metal-inhibitor interactions can also be predicted. The present review article is a collection of major advancements in the field of computational modelling for the design and testing of the corrosion inhibition effectiveness of organic corrosion inhibitors.

The effect of functionalization on solubility and plasmonic features of gold nanoparticles

Effect of functionalization on stability, solubility, and plasmonic features of gold nanoparticle with the general formula of Au₁₈(SR)₁₄ in water solvent has been studied in this work. Thiol functional groups including 1,1-mercapto-ethyl alcohol, s-cysteamine, thioglycolic acid, and beta-mercaptoethanol have been used. Electronic band-gap, excitation energies, dipole moment, and hardness for all gold nanoparticles in water solvent were investigated using the quantum mechanical approach. Intermolecular forces, radial distribution function (RDF), mean square displacement (MSD), and solvation free energy were calculated by using simulation methods. Electronic band-gap, and excitation energy analysis show that surface modification of gold nanoparticles can change their electronic and plasmonic properties. The analysis of dipole moments indicates that ligands affect the nanoparticle's solubility. An increase of hardness and therefore chemical stability can be observed for functionalized nanoparticles compared to the bare structure. Intermolecular energies analyses suggest that structure with 1,1-mercapto ethyl alcohol ligand has the strongest interaction with the solvent. The analysis of RDF diagrams also indicates that the molecule with 1,1-mercapto ethyl alcohol ligand has the sharpest pick. The slope of the linear part of MSD diagrams that is the criterion of solute's lateral diffusion is the highest value for nanoparticle with 1,1-mercapto ethyl alcohol ligand. Furthermore, functionalization also affects solvation free energy contributions. According to obtained data of quantum mechanical calculations and molecular dynamics simulations, it may be concluded that particle with 1,1-mercapto ethyl alcohol is the best ligand for increasing solubility, stability, and plasmonic functions of Au₁₈(SR)₁₄ structures among the examined ones.

Self-assembly of new O- and S-heterocycle-based protective layers for copper in acid solution

In order to explore the effects of the structures of organic molecules on their performance and develop high-efficiency self-assembly monolayers (SAMs), two heterocycle-based indole compounds, namely FYBI and TYBI, have been synthesized by a simple route. Herein, we show that FYBI and TYBI can effectively self-assemble on a copper surface and form strong anti-corrosive monolayers to protect copper in acid medium. The compositions, morphologies, and thicknesses of the SAMs have been investigated by XPS, FTIR, SEM and ellipsometry analyses. The optimal self-assembly conditions and inhibition performance of the SAMs with O- or S-heterocycles have been studied by electrochemical tests. According to the results, TYBI displays more powerful inhibition performance than FYBI. Furthermore, the high-resolution XPS and quantum calculation results reveal that the S-heterocycle indole (TYBI) can readily donate electrons to the empty d orbital of Cu and form more robust, hydrophobic, and anti-corrosive SAMs than the O-heterocycle indole (FYBI). The inhibited corrosion is achieved by inhibiting the generation of Cu2+. This systematic study on the performance of various heterocycle-based organic compounds gives a fresh perspective for forming SAMs with certain characteristics, such as anti-corrosion ability or super-hydrophobicity.

Molecular Assembly between Weak Crosslinking Cyclodextrin Polymer and trans-Cinnamaldehyde for Corrosion Inhibition towards Mild Steel in 3.5% NaCl Solution: Experimental and Theoretical Studies

Constructing molecular assembly between a soluble cyclodextrin polymer (SCDP) and an anticorrosive component is conducive to increasing the availability of a corrosion inhibitor with low molecular polarity in aqueous solution. The SCDP was prepared via the weak crosslinking effect of glutaraldehyde using β-cyclodextrin as the subunit, whose structure was confirmed by proton nuclear magnetic resonance spectra (¹H NMR), X-ray diffraction and morphology. An assembly between SCDP (host) and trans-cinnamaldehyde (guest, CA) was constructed, and the intermolecular interactions were disclosed by Fourier transform infrared spectra (FTIR). The corrosion inhibition of SCDP/CA assembly for mild steel in 3.5% NaCl solution was assessed through electrochemical and surface analyses. ¹H NMR results showed that exterior hydroxyls of β-cyclodextrin were the active sites for crosslinking. Hydrogen bonds might be the binding force between SCDP and CA according to FTIR analyses. Electrochemical measurements revealed that SCDP/CA assembly could suppress both cathodic and anodic reactions and enhance the polarization impedance for mild steel in the corrosive medium with a maximum efficiency of 92.2% at 30 °C. Surface analyses showed that CA molecules could be released from the assembly followed by the energy competition mechanism, and solely adsorb on the steel surface in parallel form, which was further evidenced by theoretical modeling.

Electrochemical Analysis of Aqueous Benzalkonium Chloride Micellar Solution and Its Mediated Electrocatalytic De-Chlorination Application

The physicochemical properties of biologically important benzalkonium chlorides (BKCs) and the effects of its structure on the de-chlorination of allyl chloride was studied by electrogenerated [Co(I)(bipyridine)3]+ (Co(I)) using an electrochemical technique. The results of [Co(II)(bipyridine)3]2+ (Co(II)) cyclic voltammetry in the presence of BKC demonstrates Co(II)/Co(III) redox couple for physicochemical analysis of BKC and Co(II)/Co(I) redox couple for catalytic application. Cyclic voltammetry over a range of scan rates and BKC concentrations revealed the BKC-bound Co(II)/Co(III) micelles showed that the identification of cmc and association of the probe Co(II) species, associated more in the hydrophobic region. In addition, change in diffusion coefficient value of Co(II)/Co(III) with BKC concentration demonstrates the association of Co(II) in micellar hydrophobic region. The beneficial effects of BKC could be accounted for by considering the benzyl headgroup-Co (II) precatalyst-volatile organic compounds (VOCs) (allyl chloride here) substrate interaction. Chromatography/mass spectroscopy (GC/MS) revealed 100% complete de-chlorination of allyl chloride accompanied by three non-chloro products. This is the first report of benzyl headgroup-induced micellar enhancement by an electrochemical method, showing that it is possible to use hydrophobic benzyl headgroup-substitution to tune the properties of micelles for various applications.

Adsorption and Computational Studies for Evaluating the Behavior of Silicon Based Compounds as Novel Corrosion Inhibitors of Carbon Steel Surfaces in Acidic Media

Two organo-silicon compounds namely; di-triethanolamine siloxane and bis (dithioamine triethanolamine) siloxane were employed as inhibitors for C-steel alloys corrosion in 1 M H2SO4 solution utilizing potentiodynamic polarization, electrochemical impedance and computational studies. According to both polarization and impedance data, it has been found that the investigated organo-silicon compounds work as efficient corrosion inhibitors and the protection aptitude raised by increasing the inhibitor concentration. The shown behavior of the tested compounds is cathodic and anodic type inhibition following Langmuir’s adsorption isotherm. The evaluated adsorption parameters, adsorption equilibrium constant (K ads) and Gibbs free energy of adsorption ( Δ G ads o ) $(\Delta G_{{\rm{ads}}}^o)$ reveal a good association between the inhibitor molecules and the surface of carbon steel in a predominantly chemisorptions manner. In the view of computational quantum and molecular dynamic simulation studies, molecular structure effectiveness and suggested mechanism of protection efficiency were discussed. Surface characterization studies such as scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) have been utilized as corroborative tools for confirming the presence of the defensive inhibitor film on the surface of a metal.

Theoretical, thermodynamic and electrochemical analysis of biotin drug as an impending corrosion inhibitor for mild steel in 15% hydrochloric acid

The corrosion mitigation efficiency of biotin drug for mild steel in 15% hydrochloric acid was thoroughly investigated by weight loss and electrochemical methods. The surface morphology was studied by the contact angle, scanning electrochemical microscopy, atomic force microscopy and scanning electron microscopy methods. Quantum chemical calculation and Fukui analysis were done to correlate the experimental and theoretical data. The influence of the concentration of inhibitor, immersion time, temperature, activation energy, enthalpy and entropy has been reported. The mitigation efficiency of biotin obtained by all methods was in good correlation with each other. Polarization studies revealed that biotin acted as a mixed inhibitor. The adsorption of biotin was found to obey the Langmuir adsorption isotherm. Surface studies showed the hydrophobic nature of the steel with inhibitor and vindicated the formation of a film on the metal surface that reduced the corrosion rate.

Experimental and theoretical studies on the corrosion inhibition of copper by two indazole derivatives in 3.0% NaCl solution

Corrosion experiments and theoretical calculations were performed to investigate the inhibition mechanism of indazole (IA) and 5-aminoindazole (AIA) for copper in NaCl solution. The results obtained from weight loss and electrochemical experiments are in good agreement, and reveal that these compounds are high-efficiency inhibitors with inhibition efficiency order: AIA>IA, which was further confirmed by field emission scanning electronic microscope (FESEM) observation. Besides, the quantum chemical calculations and molecular dynamics (MD) simulation showed that both studied inhibitors are adsorbed strongly on the copper surface in parallel mode. The adsorption of these molecules on copper substrate was found to obey Langmuir isotherm.

N-(3-(Dimethyl benzyl ammonio)propyl)alkanamide chloride derivatives as corrosion inhibitors for mild steel in 1 M HCl solution: experimental and theoretical investigation

The effects of the synthesized cationic surfactants corrosion inhibitiors DMBL, DMBM and DMBP on the corrosion of mild carbon steel in acidic medium (1.0 M HCl) were investigated using weight loss and electrochemical measurements.

Theoretical evaluation of some benzotriazole and phospono derivatives as aluminum corrosion inhibitors: DFT and molecular dynamics simulation approaches

The adsorption and corrosion inhibition properties of some benzotriazole and phospono derivatives namely, (PBTA), (TBTA), (PAA) and (PBA) molecules on the corrosion of aluminum were investigated by quantum chemical calculations and by molecular dynamics simulations.