Natural Product-Derived Phosphonic Acids as Corrosion Inhibitors for Iron and Steel

Organic acids, typically derived from an oil-based value chain, are frequently used as corrosion inhibitors in industrial metal working fluids. The criteria for selection of these corrosion inhibitors have changed in the last decades, and are today not only performance-driven, but influenced by ecological considerations, toxicity and regulatory standards. We present scalable semisynthetic approaches to organic corrosion inhibitors based on phosphonic acids from renewable resources. They have been evaluated by chip filter assay, potentiodynamic polarization measurements, electrochemical impedance measurements and gravimetry for corrosion protection of iron and steel in an aqueous environment at slightly alkaline pH. The efficacy of several phosphonic acids tested was found to be strongly dependent on structural features influencing molecular self-assembly of protective layers, and the solubility of salts formed with di- and trivalent cations from the media or formed during corrosion. A carboxyphosphonic acid (derived from castor oil) was found to have remarkable anticorrosive effects in all media tested. We attribute the anticorrosion properties of this carboxyphosphonic acid to the formation of particularly stable protective layers on the metal surface. It might thus serve as a commercially attractive substitute for current acidic corrosion inhibitors, derived from renewable resources.     

Long-Chain Alkylthia-Benzimidazoles as Corrosion Inhibitors for Carbon Steel in H2SO4 Solution

Abstract

A series of long-chain N-arylundecanamides containing benzimidazole thioethers (2a–e) were synthesized and characterized by FT IR, ¹H NMR, and elemental analysis. The corrosion inhibitory properties of these compounds on cold rolled low carbon steel metal coupons were investigated by weight loss measurements in acidic media. Surface characterization studies of the metal coupons used were performed by contact angle measurements using the sessile-drop method. In addition, the 3D image of the metal surface was measured using an optical profilometer. The results obtained from these analyses showed that almost all of the tested compounds between 25–150-ppm concentrations in acidic media are good to excellent corrosion inhibitors with the values of percentage inhibition efficiency (η) = 77–99%.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Synthesis of Cyano-Benzylidene Xanthene Synthons Using a Diprotic Brønsted Acid Catalyst,and Their Application as Efficient Inhibitors of Aluminum Corrosion in Alkaline Solutions

Novel cyano-benzylidene xanthene derivatives were synthesized using one-pot and condensation reactions. A diprotic Brønsted acid (i.e., oxalic acid) was used as an effective catalyst for the promotion of the synthesis process of the new starting xanthene–aldehyde compound. Different xanthene concentrations (ca. 0.1–2.0 mM) were applied as corrosion inhibitors to control the alkaline uniform corrosion of aluminum. Measurements were conducted in 1.0 M NaOH solution using Tafel extrapolation and linear polarization resistance (LPR) methods. The investigated xanthenes acted as mixed-type inhibitors that primarily affect the anodic process. Their inhibition efficiency values were enhanced with inhibitor concentration, and varied according to their chemical structures. At a concentration of 2.0 mM, the best-performing studied xanthene derivative recorded maximum inhibition efficiency values of 98.9% (calculated via the Tafel extrapolation method) and 98.4% (estimated via the LPR method). Scanning electron microscopy (SEM) was used to examine the morphology of the corroded and inhibited aluminum surfaces, revealing strong inhibitory action of each studied compound. High-resolution X-ray photoelectron spectroscopy (XPS) profiles validated the inhibitor compounds’ adsorption on the Al surface. Density functional theory (DFT) and Monte Carlo simulations were applied to investigate the distinction of the anticorrosive behavior among the studied xanthenes toward the Al (111) surface. The non-planarity of xanthenes and the presence of the nitrile group were the key players in the adsorption process. A match between the experimental and theoretical findings was evidenced.     

Novel Cellulose Derivatives Containing Metal (Cu,Fe, Ni) Oxide Nanoparticles as Eco-Friendly Corrosion Inhibitors for C-Steel in Acidic Chloride Solutions

Novel environmentally-friendly corrosion inhibitors based on primary aminated modified cellulose (PAC) containing nano-oxide of some metals (MONPs), for instance iron oxide nanoparticles (Fe₃O₄NPs), copper oxide nanoparticles (CuONPs), and nickel oxide nanoparticles (NiONPs), were successfully synthesized. The as-prepared PAC/MONPs nanocomposites were categorized using Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and selected area diffraction pattern (SAED) techniques. The data from spectroscopy indicated that successful formation of PAC/MONPs nanocomposites, as well as the TEM images, declared the synthesized PAC/Fe₃O₄NPs, PAC/CuONPs, and PAC/NiONPs with regular distribution with particle size diameters of 10, 23 and 43 nm, respectively. The protection performance of the as-prepared PAC and PAC/MONPs nanocomposites on the corrosion of C-steel in molar HCl was studied by the electrochemical and weight-loss approaches. The outcomes confirmed that the protection power increased with a rise in the [inhibitor]. The protection efficiency reached 88.1, 93.2, 96.1 and 98.6% with 250 ppm of PAC/CuONP, PAC/Fe₃O₄NPs, and PAC/NiONPs, respectively. PAC and all PAC/MONPs nanocomposites worked as mixed-kind inhibitors and their adsorption on the C-steel interface followed the isotherm Langmuir model. The findings were reinforced by FT-IR, FE-SEM and EDX analyses.     

An Eco-Friendly Quaternary Ammonium Salt as a Corrosion Inhibitor for Carbon Steel in 5 M HCl Solution: Theoretical and Experimental Investigation

The corrosion of industrial material is a costly problem associated with global economic losses reaching trillions of US dollars in the repair of failures. Injecting corrosion inhibitors is the most practically promising method for decelerating corrosion reactions and protecting surfaces. Recent investigations have focused on surfactants as corrosion inhibitors due to their amphiphilic nature, low cost, and simple chemical preparation procedures. This study aims to investigate the performance of an environment-friendly Quaternium-22 (Q-22) surfactant which is widely used in cosmetics for C-steel corrosion inhibition in a 5 M HCl medium. Weight loss experiments were performed at different concentrations and immersion times, presenting a maximum efficiency at 2.22 mmol·L⁻¹. The influence of Q-22 on the corrosion behavior of C-steel was elucidated using non-destructive electrochemical measurements. The overall results revealed that adding varied concentrations of Q-22 significantly decreases the corrosion rate of C-steel. The results revealed the physisorption nature of Q-22 onto the C-steel surface, with adsorption following the Freundlich isotherm (∆Hads= −16.40 kJ·mol⁻¹). The relative inhibition performance of Q-22 was also evaluated by SEM and AFM analyses. Lastly, quantum chemical calculations based on density functional theory (DFT) demonstrated that Q-22 has promising molecular features concerning the anticorrosive mechanism.     

Electrochemical and Theoretical Studies of 1-Alkyl-2-substituted Benzimidazoles as Corrosion Inhibitors for Carbon Steel Surface in HCl Medium

The inhibition efficiencies of newly synthesized four 1-alkyl-2-substituted benzimidazole compounds(a~d) have been studied for the corrosion of carbon steel in 1.0 M HCl by using potentiodynamic polarization measurement. The four inhibitors act as mixed-type inhibitors,which mainly inhibit cathodes. The inhibition efficiency of these compounds enhanced when the concentration of the inhibitors increased. A theoretical study of the corrosion inhibition efficiency of these compounds was carried out by using the B3 LYP level with the 6-31+G* basis set. Considering the solvent effect,the IEFPCM model was selected. Furthermore,the adsorption energies of the inhibitors with the iron(001) surface were studied by using molecular dynamic(MD) simulations. The theoretical results show that these inhibitors all exhibit several adsorption active-centers. Meanwhile,the MD simulations indicate that the adsorption occurs mostly through benzene ring and the lone pair electrons of the nitro atoms. These results demonstrated that the theoretical studies and MD simulations are reliable and promising methods for analyzing the inhibition efficiency of organic inhibitors.     

Synthesis and Characterization of Some Amino Acid Derived Schiff Bases Bearing Nonionic Species as Corrosion Inhibitors for Carbon Steel in 2N HCl

A novel series of nonionic amino acid Schiff-Bases were synthesized and characterized using different spectroscopic tools to elucidate their chemical structures. The surface and thermodynamic properties of these compounds were studied using classical measurements including surface and interfacial tension and emulsification tendency. The surface parameters of these compounds including surface tension, critical micelle concentration (CMC), effectiveness (π_cmc), efficiency (Pc₂₀), maximum surface excess (Γ_max), and minimum surface area (A_min) showed their good surface activity. Their thermodynamic parameters of adsorption and micellization including free energy change of micellization and adsorption showed their tendency toward adsorption at the interfaces and also micelle formation at lower concentrations. The synthesized compounds were also evaluated as corrosion inhibitors for carbon steel at different doses (400, 200, 100, 50, and 25 ppm) in 2 N HCl using gravimetric technique (weight loss). The results showed that these inhibitors are characterized by very high corrosion inhibition efficiency ranged between 99.93% and 97.98% and low corrosion rates varied between 0.09 mpy and 0.17 mpy for higher doses (400 ppm). The efficiency of inhibition was decreased by increasing the exposure time. The most efficient corrosion inhibitor of the synthesized compounds was the inhibitor which contains polyethylene oxide chain length of 23 EO units and alkyl chain length of 12 methylene groups. The effect of the hydrophobic and hydrophilic chain length in the inhibitor molecules was discussed and rationalized with their inhibition efficiency. The tendency of these inhibitors toward complexation with the transition metals was also discussed in order to explain their higher efficiency.     

Quaternary Ammonium Salts from Hydrolyzed Fatty Oil Based on Novel Tertiary Amines Used as Corrosion Inhibitors for Pipelines Carbon Steel at Acid Job in Petroleum Industry

Ten new quaternary ammonium salts (QASs) were designed and synthesized from hydrolyzed fatty oils; the hydrolyzed oils were used as a source of alkyl halides to prepare the QASs by refluxing the fatty alkyl halide with ethoxylated amines as untraditional 3° amines in acetone. The structure of the prepared QASs were characterized by FTIR and ¹H NMR spectroscopy. The prepared cationic surfactants QASs were tested as corrosion inhibitors for carbon steel in 1 M HCl solution. The corrosion inhibition efficiency was measured using weight loss and potentiodynamic polarization methods. The inhibition efficiencies obtained from the two employed methods are in good agreement with each other. In generally, the inhibition efficiency increased with increasing the inhibitor concentration. From the obtained data it was found that the inhibition efficiency of QASs, which, based on ethoxylated aromatic tertiary amine, is greater than the efficiencies of the QASs based on ethoxylated aliphatic tertiary amine. The QASs based on fatty alkyl halide from palm oil exhibited the best inhibition efficiency than QASs based on fatty alkyl halides from coconut oil. The potentiodynamic polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the inhibitors on the carbon steel surface in the acid solution was found to obey Langmuir's adsorption isotherm. The free energy of adsorption processes was calculated and discussed. The surface active properties were calculated on the basic of surface tension measurements. The obtained data of inhibition efficiencies were discussed on the light of surface active properties of these QASs and their chemical structures. The quantum chemical calculations was proceeded for QHL1,4,5 and QHP3,4,5 the following quantum chemical indices such as the bond length, bond angle, charge density distribution, highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), energy gap ΔE?HOMO –LUMO, and dipole moment (u) were considered.The surface morphology of carbon steel sample was investigated by scanning electron microscopy.     

Combined Experimental and Theoretical Insights into the Corrosion Inhibition Activity on Carbon Steel Iron of Phosphonic Acids

The inhibition effect of N,N′-phosphonomethylglycine (PMG) and vinyl phosphonic acid (VPA) on the 3% NaCl acidic solution corrosion of carbon steel iron was studied at different immersion times by potentiodynamic polarization, electrochemical impedance spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and computational methods. It is found from the polarization studies that PMG and VPA behave as mixed-type inhibitors in NaCl. Values of charge transfer resistance (R_ct) and double layer capacitance (C_dl) in the absence and presence of inhibitors are determined. The PMG and VPA inhibitors were capable of inhibiting the corrosion process up to ≈91% and ≈85%, respectively. In the presence of PMG, the synergic effect of chlorine ions was observed. Density functional theory (DFT) was engaged to establish the adsorption site of PMG, VPA, and their deprotonated states. For studied compounds, the resulted values of E_LUMO, E_HOMO, energy gap (∆E), dipole moment (μ), electronic hardness (η), global softness (σ), electrophilic index (ω), and the electronic potential map are in concordance with the experimental data results regarding their corrosion inhibition behavior and adsorption on the metal surface.     

An Integrated Experimental and Theoretical Studies on the Corrosion Inhibition of Carbon Steel by Harmal Extracts

The corrosion inhibition effect of the three extracts from Harmal roots (HRE), leaves (HLE), and flowers (HFE) were studied for carbon steel corrosion inhibition in 0.25 M H₂SO₄ solution. The electrochemical impedance study indicated that the three types of extracts decreased corrosion effectively through a charge transfer mechanism. Harmal roots and leaf extracts showed inhibition values of 94.1% and 94.2%, while it was 88.7% for Harmal flower extract at the inhibitor concentration of 82.6 ppm. Potentiodynamic polarization data revealed that Harmal extracts acted through predominant cathodic type inhibition. Both the corrosion current density and corrosion rate decreased significantly in the presence of Harmal extracts compared to blank solution. The corrosion rate (mpy) value was 63.3, 86.1, and 180.7 for HRE, HLE, and HFE, respectively. The adsorption-free energy change ΔG_ads (kJ·mol⁻¹) values calculated from the Langmuir adsorption isotherm plots were for HRE (−35.08), HLE (−33.17), and HFE (−33.12). Thus, corrosion inhibition occurred due to the adsorption of Harmal extract on the carbon steel surface via the chemisorption mechanism. Moreover, a computational investigation using B3LYP/6-311G++(d,p) basis set in both gaseous and aqueous phases was performed for the major alkaloids (1–8) present in the Harmal extract.     

Experimental and Theoretical Studies on Synthesized Compounds as Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution

Imidazole derivatives, namely, 1-((1-(piperazinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (PBIP), and 1-((1-(morpholinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (MBIP) were synthesized and investigated as inhibitors for mild steel corrosion in 15% HCl solution using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. It was found that the inhibition efficiency of both the inhibitors increases with increase in concentration of inhibitors and decreases with increase in temperature. The inhibitors, PBIP and MBIP, show corrosion inhibition efficiency of 92.6% and 91.4% at 300 ppm concentration, respectively, at 303 K. Polarization studies showed that both the studied inhibitors were of mixed type in nature. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed for surface study of uninhibited and inhibited mild steel samples. The semi-empirical AM1 method was employed for theoretical calculations.     

Garlic Powder as a Safe Environment Green Corrosion Inhibitor for Mild Steel in Acidic Media; Adsorption and Quantum Chemical Studies

The corrosion inhibition of mild steel in H3PO4 solution by garlic powder was investigated using weight loss and polarization techniques. The adsorption of garlic powder was found to obey Langmuir adsorption isotherm. Maximum inhibition efficiency was 75% at 50 °C and 250 ppm inhibitor concentration. The values of heat of adsorption were negative indicating the spontaneous adsorption process. Quantum chemical calculations were used successfully to evaluate the theoretical inhibitor efficiency. Mathematical and statistical analyses were also used to represent the corrosion rate data with high correlation coefficients. Polarization measurements showed that garlic powder was a mixed — type inhibitor.     

Cucumber (Cucumis sativus L.) Leaf Extract as a Green Corrosion Inhibitor for Carbon Steel in Acidic Solution: Electrochemical,Functional and Molecular Analysis

An extract of cucumber leaves (ECSL) was prepared as a green corrosion inhibitor for carbon steel. Its carbon steel corrosion inhibition performance against 0.5 mol L⁻¹ H₂SO₄ was investigated using electrochemical methods and scanning electron microscopy (SEM). Its composition was analyzed by gas chromatography and mass spectroscopy (GC−MS). Quantum chemical calculations and molecular dynamics simulations (MDS) were conducted to elucidate the adsorption mechanism of the inhibitor molecules on the carbon steel surface. The results indicated that the inhibition efficiency increases with its increasing concentration. The extract acted as a mixed type corrosion inhibitor, and its inhibition properties were ascribed to the geometric coverage effect induced by its adsorption on the metal surface in accordance with Langmuir’s law. The active components in the extract were identified as mainly organic compounds with functional groups such as aromatic moieties and heteroatoms. The inhibition activities of ECSL are delivered through the ability of the active components to adsorb on the metal surface through their functional groups to form a protective layer which hinders the contact of aggressive substances with carbon steel and thus suppresses its corrosion. This research provides an important reference for the design of green corrosion inhibitors based on plant waste materials.     

Performance and Mechanism of Alkylimidazolium Ionic Liquids as Corrosion Inhibitors for Copper in Sulfuric Acid Solution

The addition of corrosion inhibitors is an economic and environmental protection method to prevent the corrosion of copper. The adsorption, performance, and mechanism of three 1-alkyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO₄, [HMIM]HSO₄, and [OMIM]HSO₄) ionic liquids (ILs) on the copper surface in 0.5 M H₂SO₄ solutions were studied by quantum chemical calculation, quantitative structure-activity relationship (QSAR), and molecular dynamics simulation. It is found that the main reactive site is located on the imidazolium ring (especially the C2, N4, and N7 groups). When the alkyl chain of the imidazolium ring is increasing, the molecular reactivity of the ILs and the interaction between the ILs inhibitor and copper surface are enhanced. The imidazole ring of the ILs tends to be adsorbed on Cu (111) surface in parallel through physical adsorption. The order of adsorption energy is [Bmim]HSO₄ < [Hmim]HSO₄ < [OMIM]HSO₄, which is in agreement with the experimental order of corrosion efficiency. On the imidazole ring, the interaction between the copper surface and the C atom is greater than that between the copper surface and the N atom. It is found that ILs addition can hinder the diffusion of corrosion particles, reduce the number density of corrosion particles and slow down the corrosion rate. The order of inhibition ability of three ILs is [Bmim]HSO₄ < [Hmim]HSO₄ < [OMIM]HSO₄,which agree well with experimental results. A reliable QSAR correlation between the inhibition corrosion efficiency and molecular reactivity parameters of the ILs was established.     

Experimental,DFT and MD Assessments of Bark Extract of Tamarix aphylla as Corrosion Inhibitor for Carbon Steel Used in Desalination Plants

This study aimed to examine the extract of barks of Tamarix aphylla as a corrosion inhibitor. The methodology briefly includes plant sample collection, extraction of the corrosion inhibitor, gravimetric analysis, plotting potentiodynamic polarization plots, electrochemical impedance spectroscopic measurements, optimization of conditions, and preparation of the inhibitor products. The results show that the values of inhibition efficiency (IE%) increased as the concentrations of the inhibitor increased, with a maximum achievable inhibition efficiency of 85.0%. Potentiodynamic polarization (PP) tests revealed that the extract acts as a dual-type inhibitor. The results obtained from electrochemical impedance spectroscopy (EIS) measurements indicate an increase in polarisation resistance, confirming the inhibitive capacity of the tested inhibitor. The adsorption of the inhibitor on the steel surface follows the Langmuir adsorption isotherm model and involves competitive physio-sorption and chemisorption mechanisms. The EIS technique was utilized to investigate the effect of temperature on corrosion inhibition within the 298–328 K temperature range. Results confirm that the inhibition efficiency (IE%) of the inhibitor decreased slightly as the temperature increased. Lastly, the thermodynamic parameters for the inhibitor were calculated.     

Discovery of New VEGFR-2 Inhibitors: Design,Synthesis, Anti-Proliferative Evaluation,Docking, and MD Simulation Studies

Four new nicotinamide-based derivatives were designed as antiangiogenic VEGFR-2 inhibitors. The congeners were synthesized possessing the pharmacophoric essential features to bind correctly with the VEGFR-2 active pocket. All members were evaluated for their cytotoxic and VEGFR-2 inhibitory potentialities. Compound 6 was the most potent showingIC₅₀ values of 9.3 ± 0.02 and 7.8 ± 0.025 µM against HCT-116 and HepG-2 cells, respectively, and IC₅₀ of 60.83 nM regarding VEGFR-2 enzyme inhibition. Compound 6 arrested the growth of HCT-116 cells at the pre-G1 and G2-M phases. Further, it induced both early and late apoptosis. Additionally, compound 6 caused a significant decrease in TNF-α and IL6 by 66.42% and 57.34%, respectively. The considered compounds had similar docking performances to that of sorafenib against the VEGFR-2 (PDB ID: 2OH4). The correct binding of compound 6 with VEGFR-2 was validated using MD simulations, and MM-GPSA calculations.     

Electrochemical and Quantum Chemical Studies of Azoles as Corrosion Inhibitors for Mild Steel in Hydrochloric Acid

The inhibition effect of three azole compounds, 2-aminobenzimidazole(ABM), 2-aminothiazole(AT) and 2-aminobenzothiazole(ABT), on the corrosion of mild steel in a 1 mol/L HCl solution was investigated by means of potentiodynamic polarization measurement, electrochemical impedance spectroscopy(EIS) and scanning electron mi-croscopy(SEM). The correlation between inhibition efficiency and molecular structure of inhibitor was theoretically studied via quantum chemical calculations. The results show that the inhibition efficiency(η) of the inhibitors follows the order of η_ABT >η_AT >η_ABM. Moreover, ABM, AT and ABT belong to mixed-type inhibitors. The adsorption of the inhibitors on the steel surface follows the Langmuir adsorption isotherm, with both physisorption and chemisorption.     

Quinoline Carbonitriles as Novel Inhibitors for N80 Steel Corrosion in Oil-Well Acidizing: Experimental and Computational Insights

Russian Journal of Electrochemistry - Three quinoline derivatives as corrosion inhibitors for N80 steel 15% HCl solutions. Influence of the –H, –OCH3 groups and the introduction of...     

四种三唑化合物的合成及它们在盐酸介质中对碳钢缓蚀性能的研究

本文通过“点击化学”的方法合成了四种1,2,3-三唑化合物(3a, 3b, 4a和4b)，通过IR, ¹H NMR, ¹³C NMR 和 single crystal X-ray 晶体结构衍射分析对化合物进行了表征。通过交流阻抗和动电位扫描极化曲线研究四种化合物在1 mol/L HCl 中对碳钢的缓蚀性能。研究结果表明，四种化合物均可作为高效阳离子缓蚀剂，其中化合物4b的缓蚀效果最好，最高抑制效率可达97％。