Corrosion inhibition of mild steel by highly stable polydentate schiff base derived from 1,3- propanediamine in aqueous acidic solution

Recently, the hydrolysis of Schiff bases under experimental conditions gives suspicion for their corrosion inhibition performance. The current study employs a stable Schiff base namely, 2,2′-{propane-1,3-diylbis[azanylylidene (E) methanylylidene]}bis(6-methoxyphenol) (LPD) as corrosion inhibitor for mild steel (MS) in 1 M HCl solution. The presence of the characteristic peak of the imine group in UV-visible spectra was taken as an indicator for LPD stability in acidic media. The inhibition action was examined using electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) besides gravimetric measurement. The inhibition efficiency reached 95.93 % for 0.75 mM LPD after 24 h of immersion at 25 °C. This high efficiency is owing to the presence of the characteristic imine group and other heteroatoms and π- electrons of the aromatic benzene rings. The mechanism of inhibition depends on adsorption phenomena on mild steel surface which obeys Langmuir isotherm model. The calculated values of adsorption equilibrium constant (K_ads), adsorption free energy ΔG_ads, adsorption enthalpy ΔH_ads and adsorption entropy ΔS_ads indicated spontaneous exothermic adsorption process of both physical and chemical nature. By rising temperature, the inhibition efficiency of LPD was decreased. The calculated activation energy was increased as the concentration of LPD increased. LPD was considered as a mixed-type inhibitor as indicated from PDP measurements. The obtained surface morphology and composition analysis using SEM/EDS, AFM and FTIR techniques ensures the high efficiency of LPD as corrosion inhibitor.     

Poly(4-vinylpyridine-hexadecyl bromide) as corrosion inhibitor for mild steel in acid chloride solution

The influence of the addition of poly(4-vinylpyridine-hexadecyl bromide) P4VP-Alkyl 50?% newly synthesized on the corrosion of mild steel in molar hydrochloric acid has been investigated by weight-loss measurements combined with linear potential scan voltammetry (I?CE) and electrochemical impedance spectroscopy (EIS). The polymer reduces the corrosion rate and the inhibition efficiency (E?%) of P4VP-Alkyl 50?% increases with its concentration and attains 95?% at 300?mg/L. E?% obtained from cathodic Tafel plots, EIS, and gravimetric methods were in good agreement. The inhibitor was adsorbed on the iron surface according to the Langmuir adsorption isotherm model. Polarization measurements also show that the compound acts as a cathodic inhibitor.     

Electrochemical investigation of a schiff base synthesized by cinnamaldehyde as corrosion inhibitor on mild steel in acidic medium

The inhibiting effect of (NE)-4-phenoxy-N-(3-phenylallylidene) aniline (PAC) on the corrosion of mild steel in 1.0 M HCl has been studied by electrochemical impedance spectroscopy, and Tafel polarization measurements. The corrosion rate was also calculated theoretically in terms of mm per year and mil per year, using current density values of mild steel in 1.0 M HCl medium. It was found that PAC has a remarkable inhibition efficiency on the corrosion of mild steel especially at high temperatures. The values of E _a obtained in presence of a Schiff base were found to be lower than those obtained in the inhibitor-free solution. The increase of inhibition efficiency percent with temperature increase was associated with the transformation of physical adsorption into chemical adsorption. The thermodynamic functions of adsorption processes have been evaluated and discussed at each temperature. Scanning electron microscope observations of the electrode surface confirmed the existence of a protective adsorbed film of the inhibitor on the electrode surface.     

Experimental and theoretical approach for novel imidazolium ionic liquids as Smart Corrosion inhibitors for mild steel in 1.0 M hydrochloric acid

3-(4-hydroxybutyl)-1-phenethyl-1H-imidazol-3-ium chloride ([HB-Imid] Cl), and 3-(2-chlorobenzyl)-1-phenethyl-1H-imidazol-3-ium chloride ([CB-Imid] Cl) were investigated as corrosion inhibitors for mild steel in 1.0 M hydrochloric acid solution. Electrochemical techniques (PDP and EIS) were performed as experimental studies while DFT at B3LYP 6-311G (df,pd), and molecular dynamic simulation were used as theoretical approach. PDP experiments revealed that the studied ionic liquids (ILs) behaved as mixture type inhibitors. EIS results indicated that these compounds showed good inhibition performance with inhibition efficiency around 95% at the optimum concentration of 1.0 × 10^?3 M. According to Langmuir isotherm model and the thermodynamic parameters, these ILs were adsorbed onto the mild steel surface through physical and chemical bonds. SEM and EDX examinations proved the formation of a protective layer of adsorbed inhibitors at the steel surface. The DFT/B3LYP/6-311G(df,pd) computations in both the gas and water environments disclosed that [HB-Imid] Cl molecule was softer and had a lower energy gap, electrodonating power, and polarizability indexes.     

Synthesis and inhibition corrosion effect of two thiazole derivatives for carbon steel in 1 ​M HCl

Inhibition of C38 carbon steel corrosion by 4-methyl-3-phenyl-2(3H)-thiazolethione (TO1) and 4-methyl-2-(methylthio)-3- phenylthiazol-3-ium (ST1) in 1 ​M HCl was investigated by weight loss and electrochemical methods. All of the data obtained reveal that the two compounds act as good inhibitors in this media. At optimized concentration TO1 and ST1 showed the highest inhibition efficiency of 98.8% (2.10⁻⁴ ​M) and 93.86% (10⁻³ ​M) respectively. Polarization curves show that inhibitor molecules act as mixed type inhibitors. The impedance study showed that an increase in the concentration of the two inhibitors is accompanied by an increase in polarization resistance and a decrease in double layer capacitance. The Langmuir isotherm very well describes the adsorption of inhibitors to the surface of the corroding metal and the thermodynamic parameters showed that the adsorption of the two compounds was strong and chemical nature. X-ray photoelectron spectroscopy (XPS) confirms and describes the absorption of inhibitors under investigation on the metal surface.     

Green synthesis,electrochemical, and DFT studies on the corrosion inhibition of steel by some novel triazole Schiff base derivatives in hydrochloric acid solution

In this work, three triazole Schiff base derivatives 1-((1H-1,2,4-triazol-3-ylimino)methyl)naphthalen-2-ol (TMN), N-(furan-2-ylmethylene)-1H-1,2,4-triazol-3-amine (FTA) and N-(thiophen-2-ylmethylene)-1H-1,2,4-triazol-3-amine (TTA) were synthesized under ultrasonic irradiation and were investigated as corrosion inhibitors. FT-IR, NMR, and elemental analysis were used to elucidate the chemical structure of the synthesized inhibitors. The inhibitive characteristics of these inhibitors on C-steel corrosion in 1.0 M HCl were studied using three different techniques. The applied techniques were Electrochemical frequency modulation, electrochemical impedance spectroscopy, and potentiodynamic polarization curves. The acquired data from the experimental methods showed that the optimal concentration for TMN, FTA, and TTA is 1.0 × 10^?3 mol/L, and the inhibition efficiency reached up to 91.68%, 88.44%, and 87.29% for TMN, TTA, and FTA, respectively. Experiments also indicated that these compounds act as mixed-type inhibitors, and their concentration affects the inhibition efficiency in a directly proportional manner. Quantum paraments obtained from density functional theory (DFT) showed good agreement between experimental and computational results.     

Effect of three 2-allyl-p-mentha-6,8-dien-2-ols on inhibition of mild steel corrosion in 1 M HCl

2-Allyl-p-mentha-6,8-dien-2-ols P1−P3 synthesized from carvone P are tested as corrosion inhibitors of steel in 1 M HCl using weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods. The addition of 2-allyl-p-mentha-6,8-dien-2-ols reduced the corrosion rate. Potentiodynamic polarisation studies clearly reveal that the presence of inhibitors does not change the mechanism of hydrogen evolution and that they act essentially as cathodic inhibitors. 2-Allyl-p-mentha-6,8-dien-2-ols tested adsorb on the steel surface according to Langmuir isotherm. From the adsorption isotherm some thermodynamic data for the adsorption process are calculated and discussed. EIS measurements show the increase of the charge-transfer resistance with the inhibitor concentration. The highest inhibition efficiency (92%) is obtained for P1 at 3 g/L. The corrosion rate decreases with the rise of temperature. The corresponding activation energies are determined.     

Impedance spectroscopic study of corrosion inhibition of Al-Pure by organic Schiff base in hydrochloric acid

A new corrosion inhibitor namely o-Chloroaniline-N-benzylidene (o-CANB) has been synthesized and its inhibitive performance toward the corrosion of Al-Pure in 1.0 M hydrochloric acid has been investigated. Corrosion inhibition was studied by chemical method (weight loss) and electrochemical techniques including polarization method and electrochemical impedance spectroscopy (EIS). The present study has shown that this inhibitor is good in acidic media and the inhibition efficiency up to >99% in 1.0 M HCl. Polarization measurement revealed that the investigated inhibitor is a mixed type with a predominant action on cathode. Impedance measurement showed that the charge transfer resistance (R_ct) increased and double layer capacitance (C_dl) decreased with an increase in the inhibitor's concentration. Obtained results about inhibition efficiency from weight loss, polarization study and EIS are in good agreement with each other. The adsorption of the inhibitor on the metal surface in the acid solution was found to obey Langmuir's adsorption isotherm.     

Asymmetric synthesis of tert-butyl ((1R,4aR,8R,8aR)-1-hydroxyoctahydro-1H-isochromen-8-yl)carbamate

The asymmetric synthesis of methyl (E)-4-((1R,2S,3R)-3-amino-2-((E)-2-methoxycarbonyl-eten-1-yl)cyclohexyl)but-2-enoate 14 has been achieved from dimethyl (2E,7E)-nona-2,7-dienedioate 2. A key step is the asymmetric synthesis of 1-hydroxyoctahydro-1H-isochromene derivative 5 whose X-ray analysis corroborated the stereochemistry of the new stereocenters. The asymmetric synthesis of the isochromenyl acetate derivative 11 shows the potential of this methodology for fused cyclohexanic system heterocyclic synthesis.     

Study on the corrosion inhibition of biomass carbon quantum dot self- aggregation on Q235 steel in hydrochloric acid

At present, the development of efficient green corrosion inhibitors has become one of the important directions of metal corrosion protection. In this paper, biomass carbon quantum dots (BCQDs) were prepared by hydrothermal reaction using biomass precursors. The optical properties and structural composition of the synthesized BCQDs were characterized in detail. After that, the corrosion inhibition performance of BCQDs was evaluated by EIS, Tafel, SEM and TEM. The electrochemistry and surface tests demonstrate that the aggregates can effectively prevent Q235 steel from corrosion in 1 M HCl medium at 298 K-328 K, with the maximum inhibition efficiency of 94.1 % at the concentration of 200 mg/L at 308 K. Finally, the corrosion inhibition mechanism was analyzed by FTIR, CA and XPS on the surface of the corroded carbon steel samples. The inhibition mechanism suggests that BCQDs can inhibit metal corrosion by self-aggregation and adsorption on metal surface. This is owing to its small size effect and functional groups containing heteroatoms, easily forming dense protective film.     

Syntheses, characterization and crystal structures of new mono- and bis-Schiff base compounds derived from 1,2,4-triazine and the silver(I) complexes containing mono-Schiff base ligands

Some new Schiff bases, (Z)-4-amino-3-((E)-(R-methoxybenzylidene)hydrazono)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L2), R?=?3 (L3) and R?=?4 (L4)), were synthesized by the condensation reactions of 4-amino-3-hydrazinyl-6-methyl-1,2,4-triazin-5(4H)-one (L1) and corresponding methoxybenzaldehyde in a molar ratio 1:1.5 in high yields. The reaction of L2 and L4 with an excess amount of the corresponding aldehydes gave the unsymmetrical bis-Schiff bases (E)-3-((E)-(R-methoxybenzylidene)hydrazono)-4-((E)-R-methoxybenzylideneamino)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L22) and R?=?4 (L44)), respectively. Furthermore, the reaction of L2?CL4 with silver(I) nitrate in a molar ratio 2:1 led to the silver(I)-complexes with the general formula [Ag(Lx)₂]NO₃ (Lx?=?L2 (2), L3 (3) and L4 (4)). All synthesized Schiff base compounds and complexes were characterized by a combination of IR-, ¹H-NMR spectroscopy, mass spectrometry and elemental analyses. In addition, the structures of L2, L4·CH₃CN, L22·CH₃OH and L44·CH₃OH and complexes 2 and 4 were determined by X-ray diffraction studies.     

Corrosion inhibition of steel in molar HCl by triphenyltin2–thiophene carboxylate

The effect of triphenyltin2–thiophene carboxylate (TTC) on the corrosion of steel in hydrochloric acid medium was studied using gravimetric, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitor to reach 97% at 10^?3 M. Polarisation study shows that TTC is an efficient inhibitor and acts as a mixed-type inhibitor. EIS results indicate the increase of resistance transfer (R_T) and the decrease of double layer capacitance (C_dl) with TTC concentration. Triphenyltin2–thiophene carboxylate molecules lead to the formation of a protective layer on the surface of steel. The inhibitor is adsorbed on the steel surface according to Langmuir isotherm.     

Thermal study on complexes with Schiff base derived from 1,2,4-triazole as potential antimicrobial agents

In order to develop new metallo-antimicrobials the complexes of type MLCl·nH₂O ((1) M: Co, n = 0; (2) M: Ni, n = 2; (3) M: Cu, n = 2.5; (4) M: Zn, n = 0, HL: Schiff base derived from acetylacetone and 3-amino-4H-1,2,4-triazole) were synthesized by template condensation. The features of complexes have been assigned from microanalytical, IR and UV–Vis-NIR data. The species heating in air evidenced processes as melting, water and hydrochloride endothermic elimination as well as oxidative degradation of the Schiff base. The temperature ranges as well as modification in the electronic spectra of dehydrated intermediates indicate the presence of both coordination and crystallisation water molecules. The final product of decomposition was the most stable metal oxide as powder X-ray diffraction indicated.     

Corrosion inhibition of aluminum in 1 M H3PO4 solutions by ethanolamines

The inhibitive effect of the investigated compounds (ethanolamine (I), diethanolamine (II) and triethanolamine (III)) on the corrosion behavior of aluminum in 1 M H₃PO₄ solution using weight loss, galvanostatic polarization and quantum chemical calculation methods was studied. The inhibition efficiency was found to depend on type and concentration of the additives and also on temperature. The effect of addition of halide ions to various concentrations of these compounds has also been studied. The apparent activation energy (E_a) and other thermodynamic parameters for the corrosion process have also been calculated and discussed. The galvanostatic polarization data indicated that these inhibitors were of mixed-type. The slopes of the cathodic and anodic Tafel lines (β_c and β_a) are approximately constant and independent of the inhibitor concentration. The adsorption of these compounds on aluminum surface has been found to obey the Freundlich adsorption isotherm. Some quantum chemical parameters and Mulliken charge densities for investigated compounds were calculated by the AM1 semi-empirical method to provide further insight into the mechanism of inhibition of the corrosion process. The theoretical results are then compared with experimental data.     

Corrosion inhibition of copper in chloride media by 2-mercapto-4-(p-methoxyphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile: Electrochemical and theoretical study

Electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization have been used to investigate the inhibition effect of a new pyrimidine heterocyclic derivative, namely 2-mercapto-4-(p-methoxyphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile (MPD) on copper corrosion in 3.5% NaCl solutions at 25 ± 1 °C. The electrochemical investigations showed that MPD gives sufficient inhibition against copper corrosion in 3.5% NaCl solutions. Potentiodynamic polarization measurements have shown that the MPD inhibit both the cathodic and anodic processes and thus it classified as mixed-type inhibitor. EIS measurements indicate that the values of constant phase elements (CPEs) tend to decrease and both charge-transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. Electrochemical kinetic parameters obtained using EFM methods were comparable with that calculated from traditional measurements (EIS and potentiodynamic polarization). Molecular simulation technique was used to investigate the adsorption configuration of MPD on copper surface. Number of electrons transferred from MPD to the copper surface was calculated by semi-empirical quantum chemical calculations.     

Synthesis,characterization, and antibacterial activity of two zinc(II) complexes with Schiff bases derived from rimantadine

The reactions of zinc(II) chloride and two Schiff base ligands derived from rimantadine and 5-chlorosalicylaldehyde/4-methoxysalicylaldehydes, generated two novel complexes [Zn(L¹)₂Cl₂] (I) and [Zn(L²)₂Cl₂] (II), where L¹ = 2-((1-(1-adamantan-1-yl)ethyl)-iminomethyl)-4-chlorophenol, L² = 2-((1-(1-adamantan-1-yl)ethyl)iminomethyl)-5-methoxyphenol. The complexes were characterized by the means of IR, ¹H NMR, elemental analysis, molar conductance and thermal analysis. A single-crystal X-ray diffraction analysis reveals that both complexes crystallize in orthorhombic system, space group Fdd2 for I and Pbcn for II. In two complexes crystals, each asymmetric unit consists of one zinc(II) ion, two corresponding Schiff base ligands and two chlorine atoms; the central zinc atom lies on a twofold rotation axis and is four-coordinate via two chlorine atoms and two oxygen atoms from the Schiff base ligands, forming a distorted tetrahedral geometry.     

Synthesis and evaluation of novel O-functionalized aminated chitosan derivatives as antibacterial,antioxidant and anticorrosion for 316L stainless steel in simulated body fluid

Chitosan’s Schiff base derivatives are taking the attention of scientists as a promising biomaterial for various applications. In this study, O-functionalized aminated chitosan (O-F-Am-Ch) was coupled with 4,4-dimethyl amino-benzaldehyde and N-methyl-2-pyrrolidone to produce Schiff bases (I) and (II), respectively. The chemical and physical properties of the new derivatives were investigated by Fourier transform infrared (FT-IR) that show a significant band for C=C between 1400 and 1600 cm⁻¹, thermal gravimetric analysis (TGA), which demonstrate an increase in the thermal stability of new derivatives than O-F-Am-Ch and scanning electron microscope (SEM) that indicates a slight increase in the rough structure of the surface. In addition, 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assays that examined the antioxidant properties of the new Schiff bases. The biocidal activity against four different bacterial strains [two gram-negative (Pseudomonas aeruginosa and Escherichia coli) and two gram-positive (Bacillus cereus and Staphylococcus aureus)] demonstrates significant improvement of the inhibition activity compare to O-F-Am-Ch with more activity against Gram-negative bacteria than that against gram-positive bacteria.As an implanted alloy, 316L stainless steel is used as a temporary biomaterial in different countries without any pretreatment. Our study focused on further improving the alloy features by investigating the protection efficiency of O-F-Am-Ch and the synthesized Schiff bases for the 316L stainless steel surface against corrosion in simulated body fluid (SBF). The corrosion inhibition of these compounds was investigated using two electrochemical methods (potentiodynamic polarization technique and electrochemical impedance spectroscopy). The results suggested the formation of self-assembled monolayers (SAMs) of the compounds under investigation. Furthermore, they demonstrated a considerable dose-dependent inhibiting corrosion of 316L stainless steel in SBF, whereas the inhibition efficiency exceeds 77% at 1000 ppm for the Schiff bases II. In conclusion, the tested derivatives show promising properties to refine stainless steel for implant applications.     

Electrochemical and computational studies of an expired vilazodone Drug as environmentally safe corrosion inhibitor for aluminum in chloride medium

Through using chemical and electrochemical methods, the theoretical and experimental investigation of the expired vilazodone drug's ability to prevent corrosion on aluminium (Al) in a corrosive medium of HCl (1 M) has been examined. Weighing tests (WL), electrochemical (impedance spectroscopy (EIS), potentiodynamic polarization (PDP)), atomic force microscopy (AFM), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) tests at 25 °C have all been used to investigate Vilazodone's capability to prevent corrosion of Al in 1 M HCl in the concentration in the range of 25–150 ppm. The corrosion inhibition effect of the investigate Vilazodone's against Al in acid environment was investigated weight loss and electrochemical methods. The highest % inhibition efficiency (%IE) was 95% resulted from weight loss technique at the highest concentration for inhibitor. According to the PDP data, this examined vilazodone function as a mixed-type inhibitor, impacting both the anodic and cathodic reactions. The inhibitors covered the active points of the metal surface, according to electrochemical impedance spectroscopy (EIS), to prevent corrosion. It was discovered that the inhibitor adsorption on the Al surface obeyed the Langmuir adsorption isothermal model. AFM, SEM, and FTIR surface examinations proved the inhibitor had a significant protective effect against Al dissolution in 1 M HCl. The outcomes from chemical and electrochemical methods are relatively consistent. Vilazodone acted as an effective corrosion inhibitor, according to all of the experimental data.     

Performance of dodecyl dimethyl benzyl ammonium chloride as bactericide and corrosion inhibitor for 7B04 aluminum alloy in an aircraft fuel system

In this study, the broad-spectrum antimicrobial property of dodecyl dimethyl benzyl ammonium chloride (DDBAC) was investigated against three species of bacteria, Lysinibacillus sphaericus (L. sphaericus), Acinetobacter lwoffii (A. lwoffii), and Sediminibacterium salmoneum (S. salmoneum) isolated and purified from a naval aircraft fuel system. Through the inhibition zone method and minimum inhibitory concentration test, DDBAC was found to have a good antimicrobial performance with a minimum inhibitory concentration of 64 mg/L. The influence of DDBAC on the corrosion behavior of fuel tank material was evaluated by electrochemical measurements, such as polarization curve and electrochemical impedance spectroscopy (EIS). The polarization curve indicated that DDBAC suppressed anodic and cathodic reactions as a mixed-type corrosion inhibitor, and the inhibition efficiency was 68.38% at the concentration of 80 mg/L after 28 days of immersion. The EIS results showed that DDBAC inhibited the corrosion of 7B04 aluminum alloy in the concentration range of 40–120 mg/L. The DDBAC adsorption on the aluminum alloy surface was in agreement with the modified Langmuir adsorption isotherm model. The quantum chemical calculations proved that a lone pair of electrons of nitrogen atoms in DDBAC were able to form coordinate bonds with the empty orbital in aluminum, resulting in a tight chemisorption layer on the aluminum alloy surface and corrosion inhibition.     

On the corrosion inhibition of iron in hydrochloric acid solutions,Part I: Electrochemical DC and AC studies

The inhibitive action of 4-methyl pyrazole (4MP) against the corrosion of iron (99.9999%) in solutions of hydrochloric acid has been studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). At inhibitor concentration range (10^?3–10^?2 M) in 1.0 M acid, the results showed that 4MP suppressed mainly the anodic processes of iron corrosion in 1.0 M HCl by adsorption on the iron surface according to Temkin adsorption isotherm. Both potentiodynamic and EIS measurements reveal that 4MP inhibits the iron corrosion in 1.0 M HCl and that the efficiency increases with increasing inhibitor concentration. Data obtained from EIS were analyzed to model the corrosion inhibition process through an equivalent circuit.