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Active constituents of Chinese yam peel (CYPE), namely, diosgenin (DOG), batatasin-I (BTS-I), batatasin-III (BTS-III), and yam polysaccharide (Y-PS), were extracted via an ultrasonic soaking strategy. The synergetic anticorrosion mechanism among these compounds for copper in artificial seawater (ASW) was clarified by gravimetric measurements, electrochemical evaluations, surface analyses, quantum chemical calculations under a dominant solvent model, and molecular dynamics (MD) simulations. The results of weight loss revealed that CYPE strongly inhibited the corrosion of copper in ASW, and the elevating temperature boosted the anticorrosion efficacy of CYPE. The inhibition efficiency could attain 96.33% with 900 mg/L CYPE in ASW at 298 K due to effective adsorption. CYPE simultaneously suppressed the anodic and cathodic reactions for copper in ASW, which could be categorized as the mixed-type corrosion inhibitor with the predominant anodic effect. Similar electrochemical kinetics was evidenced by electrochemical frequency modulation (EFM). Electrochemical impedance spectroscopy (EIS) indicated that CYPE prominently increased the charge-transfer resistance at the copper/electrolyte interface without altering the corrosion mechanism. Extending the immersion time was also conducive for CYPE to further minimize the corrosion of copper in ASW, which was demonstrated by the time-course polarization, EIS, and EFM tests. Owing to the adsorption of CYPE, the copper surface was well-protected and showed reduced wettability and limited variation of roughness. From the outcomes of quantum chemical calculations, global and local reactive descriptors of DOG implied the cross-linked deposition of actually formed dioscin on the copper surface; otherwise, those of BTS-I/-III showed the propensity for parallel adsorption, which could chemically anchor on the voids uncovered by dioscin and thereby synergistically inhibit the corrosion process. The adsorption orientations of DOG, BTS-I, and BTS-III were also consolidated by MD simulations. The findings of this study might be beneficial to inspire the development of eco-friendly corrosion inhibitors from plant wastes for copper in marine environments.

The inhibitive effect and inhibition mechanism of l-lysine derivatives, namely α-N-benzyloxycarbonyl-l-lysine (α-NL) and e-N-benzyloxycarbonyl-l-lysine (e-NL), on the corrosion of carbon steel in 0.5 M H2SO4 solution were investigated by electrochemical technique, weightlessness test, scanning electron microscope, atomic force microscope, infrared attenuated reflectance spectroscopy and quantum chemical calculation. The results showed that α-NL and e-NL as moderate cathodic inhibitors mainly inhibited the cathodic reaction of carbon steel in 0.5 M H2SO4 solution, and the terminal substituted e-NL showed better corrosion inhibition than the α-N-benzyloxycarbonyl protected α-NL. Their inhibition efficiencies increased with the increase in inhibitor concentration, and the inhibition efficiency of α-NL and e-NL with concentration of 10 mmol can reach 53.4% and 61.5%, respectively, but decreased with rising temperature. The adsorption of investigated inhibitors on the surface of carbon steel obeyed the modified Langmuir isotherm and El-Awady thermodynamic-kinetic model, and the thermodynamic and kinetic parameters were determined to discuss the mechanism of inhibition of α-NL and e-NL. Moreover, Quantum chemical calculation gave further insight into the inhibition mechanism of α-NL and e-NL and was employed to reveal the reasons for their differences in inhibition performance.

The mutually corroborated electrochemical measurements and theoretical calculations were used to investigate the corrosion inhibition performances of purpald (4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, AHMT) and its synergistic effect with tartaric acid (TA) on mild steel in 0.5 M H2SO4 solution. The experimental results show that the inhibition efficiency increases with the concentration of AHMT and increases further when TA exists. Density functional theory (DFT) calculations were performed to interpret the measured data and trends observed in the electrochemical studies. Furthermore, molecular dynamic simulation revealed a nearly flat configuration for molecules on metal surface with negative adsorption energies in a sequence agreed with experimental observation.

The ethanol extract of bamboo shoots was obtained by refluxing bamboo shoots in 95 % ethanol, and then the ethanol extract from bamboo shoots were separated by organic solvents with different polarity, including petroleum ether, dichloromethane, ethyl acetate and n-butanol. The inhibitive effect of different solvent extraction fractions of bamboo shoot extract on the corrosion of mild steel in 0.5 mol/L H2SO4 solution was investigated through electrochemical technique, weight loss test, scanning electron microscope and X-ray photoelectron spectroscopy. Electrochemical results showed that all extraction fractions of bamboo shoots extract, as modest cathodic inhibitors, mainly inhibited the cathodic reaction of mild steel in 0.5 mol/L H2SO4 solution, and the inhibition efficiency of extraction fraction increased with the increase in its concentration. When the concentration was 0.4 g/L, the corrosion inhibition efficiency of dichloromethane fraction (DCMF), n-butanol fraction (nBF), ethyl acetate fraction (EAF) and the residual fraction (RF) are 93.03%, 89.62%, 85.33% and 64.84%, respectively. However, the results of weight loss experiment showed that when the experimental time increased from 4 h to 24 h, the inhibition efficiency of DCMF and EAF decreased significantly, but that of nBF remained at about 86%, showing a better long-term effect. Surface analysis technology was used to investigate the corrosion inhibition and adsorption behavior of the extraction extraction fractions, and the adsorption of different solvent extraction fractions of bamboo shoot ethanol extract on mild steel surface was in accordance with the equation of Langmuir isotherm.

In this work, nitrogen-doped carbon dots (NCDs) were obtained by hydrothermal method with citric acid and ethylenediamine as precursors. The corrosion inhibition performance and mechanism of prepared the NCDs on the Q235 carbon steel in 1 M HCl solution were evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curve, and surface analysis. The results that the NCDs exhibited 93% of inhibition efficiency at 100 mg/L. Electrochemical measurements demonstrated that the NCDs adsorbed on the metal surface and effectively inhibited the electron transfer process. The potentiodynamic polarization suggested that NCDs were excellent mix-type corrosion inhibition. Furthermore, NCDs successfully prevented the dissolution of anode metal and the evolution of cathode hydrogen ions. The adsorption of the NCDs followed Langmuir adsorption isotherm indicated physical and chemical adsorption. At the same time, the adsorption mechanism was analyzed, guiding the use of carbon dots as environment-friendly corrosion inhibitors in the future.

In this work, we used experimental and theoretical calculation methods to investigate the corrosion inhibition nature of banana leaves water extract (BLWE) for X70 steel at 1 mol/L hydrochloric acid environment. The data of electrochemical tests manifest that the hydrochloric acid medium will accelerate the corrosion of X70 steel with increasing temperature. The charge transfer resistance dropped sharply from 55 Ω cm2 at 298 K to 18.4 Ω cm2 at 313 K. After adding BLWE in hydrochloric acid solution, the anti-corrosion efficiency of banana leaves extract for X70 steel can be maintained at about 90%. BLWE can simultaneously inhibit the anodic and cathodic reactions of X70 steel in hydrochloric acid solution, so it is mixed-type inhibitor. Surface morphology analysis strongly shows that BLWE can effectually restrain the corrosion of X70 steel. BLWE adsorption at the X70 steel surface is accord with Langmuir single-deck adsorption. Quantum chemical (QC) calculation and molecular dynamics simulations (MDS) have shown that (S)-2-amino-3-(4-hydroxyphenyl)propanoic acid (AHP), 3-(2-aminoethyl)-1H-indol-5-ol (ATI), and 3,4-Dihydroxycinnamic Acid (DDA) in BLWE can show excellent anti-corrosion character. QC calculation results show that AHP, ATI and DDA have small dipole moment values. The small dipole moment value is favorable the accumulation of inhibitor molecule on the X70 steel surface, thereby forming a denser barrier film. MDS results show that AHP, ATI and DDA can be adsorbed on the Fe (110) surface in parallel to obtain the maximum coverage.

The corrosion inhibition performance of 5-Mercapto-1-phenyltetrazole (MPT) has been studied using theoretical calculation and abundant experimental methods. Electrochemical experiments show that MPT show high-efficiency corrosion inhibition ability for Q235 steel in H2SO4 environment. The concentration of MPT is 5 mM, the anti-corrosion inhibition efficiency (η) is 98.1% at the 298 K. Besides, the anti-corrosion nature of MPT can keep about 98% in the temperature district of 298 K to 318 K. The test results of atomic force microscope (AFM) and scanning electron microscope (SEM) strongly prove that MPT can effectively adsorb at the Q235 steel interface, thereby effectively inhibiting the Q235 steel corrosion. The adsorption of MPT at the interface of Q235 steel conforms to Langmuir single-deck adsorption, and both physical and chemical adsorption exist. The theoretically calculated surface MPT has a large dipole moment and a small energy gap value, so it can exhibit high-quality corrosion inhibition performance.

WOS: 000403012700051, One of the effective methods developed to inhibit the corrosion of steel is the use of organic molecules as corrosion inhibitors. In particular, the design and synthesis of large size organic corrosion inhibitors draws more and more attention. Unfortunately, an atomic-level insight into the inhibition mechanism is still lacking, and regular density functional theory method is found to be inefficient in dealing with large inhibitor-metal adsorption systems. Given this background, in this work, density functional based tight binding (DFTB) approach was used to investigate the adsorption properties of three large size inhibitors (i.e., chalcone derivatives) on an iron surface. The molecular activity of free chalcone derivatives was studied by means of Frontier molecular orbital theory. The growth characteristics of alpha-Fe habits were observed using the "Morphology" software. Some adsorption parameters such as charge density difference, density of states, and changes of molecular orbital were described in detail. The present study is helpful to understand the anticorrosive mechanism of similar organic inhibitors and provides a feasible way to develop novel corrosion inhibitors., Science and Technology Program of Guizhou Province [QKHJC 2016-1149]; Guizhou Provincial Department of Education Foundation [QJHKYZ2016105, 2016-009]; Research Fund for the Doctoral Program of Tongren University [trxyDH1510]; National Natural Science Foundation of China [51462030]; Student's Platform for Innovation and Entrepreneurship Training Program [2016106665]; Opening Project of Sichuan University of Science and Engineering [2016CL06], This research was sponsored by the Science and Technology Program of Guizhou Province (QKHJC 2016-1149), the Guizhou Provincial Department of Education Foundation (QJHKYZ2016105, 2016-009), the Research Fund for the Doctoral Program of Tongren University (trxyDH1510), the National Natural Science Foundation of China (51462030), the Student's Platform for Innovation and Entrepreneurship Training Program (2016106665), and the Opening Project of Sichuan University of Science and Engineering (2016CL06).

Here, S-allyl-O,O′-diphenyldithiophosphate(SOD1), S-allyl-O,O′-dibenzyldithiophosphate (SOD2) and S-allyl-O,O′-di(2-phenylethyl)dithiophosphate(SOD3) were successful synthesized and characterized, which acting as the novel corrosion inhibitors for mild steel in hydrochloric acid (HCl) solution were evaluated by electrochemical measurements, weight loss measurement and scanning electron microscopy. Potentiodynamic polarization measurement indicates that the synthesized inhibitors are effective mixed-type inhibitors. The inhibition efficiency increases with inhibitor concentration increasing, decreases with HCl concentration and temperature increasing. The adsorption of SOD1, SOD2 and SOD3 on mild steel surface obeys Langmuir isotherm. The adsorption of SOD1 and SOD3 on mild steel surface is a mixed adsorption involving both physisorption and chemisorption, and that the adsorption of SOD2 on mild steel surface belongs to chemical adsorption. Keywords: Corrosion inhibitor, Mild steel, Polarization, Weight loss, Adsorption

In this paper, the corrosion inhibition performance of eco-friendly corrosion inhibitors 1-propyl-3-methylimidazolium bromide ([PrMIm]Br), 1-aminopropyl-3-methylimidazolium bromide ([APMIm]Br) and 1,4-bis(3-methylimidazolium-1-yl)butane dibromide ([BMImB]Br2) was investigated for mild steel (MS) in H2SO4 medium via experimental and theoretical methods. The results of electrochemical experiments show that the order of their corrosion inhibition is [BMImB]Br2 > [APMIm]Br > [PrMIm]Br. The corrosion inhibition efficiency of [BMImB]Br2, [APMIm]Br and [PrMIm]Br are 92.9%, 88.0%, and 69.6% at the 303 K, respectively. The scanning electron microscope (SEM) morphology test results vividly prove that [BMImB]Br2 has higher corrosion inhibition performance for [APMIm]Br and [PrMIm]Br. Weight loss experiments show that [BMImB]Br2 and [APMIm]Br can still exhibit good corrosion inhibition nature with increasing temperature. Besides, the adsorption of three imidazole ionic liquids on the MS/solution interface is conform to Langmuir single-layer model, and they belong to the physical and chemical adsorption on the MS surface. Theoretical calculations explain their corrosion inhibition mechanism from an atomic or molecule perspective.

In this work, we studied food flavor 2-Furfurylthio-3-methylpyrazine (FFM) as the green inhibitor for copper corrosion H2SO4 solution. Electrochemical experiment data show that FFM can exhibit prominent anti-corrosion nature for copper in H2SO4 medium in the temperature range of 298 K to 313 K. Potentiodynamic polarization curve results show that the corrosion inhibition efficiency of FFM can be as high as 97.9% at a concentration of 5 mmol/L. The surface morphology test results show that adding 5 mmol/L FFM in H2SO4 medium, the copper sample is still relatively flat after soaking for 20 h, and the roughness values is only 7.84 nm. The XPS experimental results show that the S and N atoms in the FFM molecule can form N Cu and S Cu bonds on the copper surface to generate chemical adsorption. Besides, the FFM adsorption on the copper/solution surface conforms to the Langmuir monolayer adsorption model. The theoretical calculation results also prove that FFM can exhibit prominent anti-corrosion nature for copper in sulfuric acid medium.

The inhibition performance and mechanism of loquat leaves extract (LLE) for the corrosion of mild steel in 0.5 M H2SO4 were investigated using weight loss method, electrochemical measurements and scanning electron microscope (SEM). The results revealed that LLE acted as a modest cathodic inhibitor, its inhibition efficiency increased with the concentration of LLE and reached a maximum value of 96% at the 100% V/V concentration, but decreased with incremental temperature. Besides, it was found that the adsorption of LLE on steel surface obeyed Langmuir adsorption isotherm, and then the thermodynamic and kinetic parameters were further determined accordingly. Furthermore, LLE was preliminarily separated by pH-gradient sedimentation and the synergistic inhibition between the isolates was investigated.

The inhibition performance and mechanism of 1-octyl-3-methylimidazolium bromide ([OMIM]Br) and 1-allyl-3-octylimidazolium bromide ([AOIM]Br) for the corrosion of mild steel in 0.5 M H2SO4 were investigated using weight loss method, electrochemical measurements, scanning electron microscope (SEM) and quantum chemical calculation. The results revealed that [OMIM]Br and [AOIM]Br acted as modest cathodic inhibitors, and due to the electron-donating effect of allyl group, [AOIM]Br showed better inhibitive performance. The adsorption of both inhibitors on steel surface obeyed El-Awady thermodynamic–kinetic model, thus the thermodynamic and kinetic parameters were calculated and discussed. Moreover, theoretical calculation was used to investigate inhibition mechanism of studied inhibitors.

The work presents the combined effect of methionine molecules and cuprous oxide passive film on the corrosion inhibition of copper in 1 M NaOH solution by using potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy/energy dispersive X-ray analysis and theoretical calculations. The results reveal that methionine is an effective inhibitor for copper in 1 M NaOH solution and its inhibition efficiency is increased by increasing its concentration. Also, the electrochemical results showed that methionine mainly suppresses the cathodic process as a cathodic-typed inhibitor by adsorption, and the adsorption of methionine can occur on the passive film surface (cuprous oxide) of copper. The adsorbed film of inhibitors combines with the cuprous oxide passive film, and provides a double-layer protection for copper in alkaline solution. Quantum chemical calculation was applied to investigate the inhibition mechanism of methionine, and molecular dynamics simulation was further performed to illustrate the double-layer protection system for copper in alkaline solution.

WOS: 000410464300053, PubMed ID: 28755643, The mutually corroborated density functional theory (DFT) and molecular dynamics (MD) simulation methodology were employed to evaluate the inhibition performance of three thiourea derivatives (Inhl, Inh2, and Inh3) on carbon steel corrosion. Experimental results have shown that the corrosion rate follows the order: Inh3 > Inh2 > Inhl. Quantum chemical descriptors such as the frontier orbital energies (E-Homo and E-Lumo), the energy gap between E-LUMO and E-Homo (Delta E), dipole moment (mu), and Fukui index have been calculated and discussed. Some significant factors such as solvent, temperature, and coverage have been considered when investigating the adsorption of aforementioned thiourea derivatives on Fe (1 1 0) surface. Our results provide important atomic/molecular insights into the anticorrosive mechanism of inhibitor molecules, which could help in understanding the organic-metal interface and designing more appropriate organic corrosion inhibitors. (C) 2017 Elsevier Inc. All rights reserved., Science and Technology Program of Guizhou Province [QKHJC2016-1149]; Sichuan University of Science and Engineering [2016CL06]; Tongren University [trxyDH1510]; Student's Platform for Innovation and Entrepreneurship Training Program [2016106665]; Guizhou Provincial Department of Education Foundation [QJHKYZ2016-105, 2016-009], This research was sponsored by the Science and Technology Program of Guizhou Province (QKHJC2016-1149), the Opening Project of Sichuan University of Science and Engineering (2016CL06), the Research Fund for the Doctoral Program of Tongren University (trxyDH1510), the Student's Platform for Innovation and Entrepreneurship Training Program (2016106665), and the Guizhou Provincial Department of Education Foundation (QJHKYZ2016-105, 2016-009). We would like to thank the anonymous referees for valuable criticisms and useful suggestions that helped us to improve the quality of our present and future work.

A newly amino acid ionic liquid, 1-octyl-3-methylimidazolium l-prolinate ([Omim]Lpro), was investigated as the inhibitor for mild steel in 0.5 M H2SO4 solution using weight loss method, electrochemical measurements, scanning electron microscopy (SEM), and quantum chemical calculation. The obtained results revealed that [Omim]Lpro was a mixed-type inhibitor with a predominantly cathodic action for mild steel in 0.5 M H2SO4 solution, and inhibition efficiency reached nearly 80% at the concentration of 10 mM, in which the Omim cation played a major role in the corrosion inhibition of [Omim]Lpro. The adsorption of [Omim]Lpro on the mild steel surface was found to obey the El-Awady thermodynamic-kinetic model and Flory–Huggins isotherm equations; thus the thermodynamic and kinetic parameters governing the adsorption process were calculated and discussed. Moreover, quantum chemical calculation gave further insight into the mechanism of inhibition of [Omim]Lpro.

A newly benzimidazole derivative, 1-butyl-3-methyl-1 H -benzimidazolium iodide (BMBIMI), has been tested as inhibitor for mild steel in 0.5 M H 2 SO 4 solution via various approaches including weight loss, electrochemical measurements, scanning electron microscope (SEM), atomic force microscope (AFM) and theoretical calculations. The obtained results reveal that BMBIMI is an effective mixed-type corrosion inhibitor for mild steel, and the adsorption of BMBIMI on the mild steel surface is found to obey the Langmuir adsorption isotherm, thus the thermodynamic and kinetic parameters governing the adsorption process are calculated and discussed. Moreover, theoretical calculations give further insight into the mechanism of inhibition of BMBIMI.

Copper is an important industrial material. Adding organic compounds have proved to be very efficient for copper protection. However, an atomic-level insight into the adsorption and inhibition mechanism is still lacked. In this work, the adsorption of a benzotriazole derivative (BTD for short) on Cu (111) surface has been studied by density functional theory (DFT) and molecular dynamics (MD) methods. Some salient parameters such as adsorption energy, charge density difference, and density of states were detailed described. The MD simulation indicates that the adsorption process of BTD on copper surface is very fast. The findings will contribute to the understanding of the anticorrosive mechanism of similar organic inhibitors.