Some Schiff Base Surfactants as Steel-Corrosion Inhibitors

Two series of Schiff base amphiphiles were prepared by condensation of benzaldehyde or anisaldehyde with three different alkyl chain length fatty amines namely: dodecyl, hexadecyl and octadecyl amine. The chemical structures of the prepared Schiff bases were confirmed by using different techniques, (elemental analysis, FTIR and ¹H-NMR spectra). The data of structural analysis for these compounds were confirmed by the purity of the synthesized amphiphiles. The synthesized Schiff bases were evaluated as corrosion inhibitors for low carbon steel (mild steel) in various acidic media (HCl and H₂SO₄) using a weight loss technique. The corrosion inhibition measurements of these inhibitors showed high protection against corrosion process in the tested acidic media at different doses (50, 100, 150 and 200 ppm) as well as their having a good biocidal effect against sulphate reducing bacteria. The discussion correlated the efficient corrosion inhibition of these inhibitors to their chemical structures.     

Environmentally safe corrosion inhibition of the Cu–Ni alloys in acidic sulfate solutions

The corrosion and passivation behaviors of alloys with different Cu–Ni ratios were investigated in acidic sulfate solutions. The corrosion rate was calculated and the corrosion inhibition process was investigated using different amino acids as corrosion inhibitors. For these investigations conventional electrochemical techniques and electrochemical impedance spectroscopy (EIS) were used. Fitting of the experimental impedance data to theoretical values enables understanding of the corrosion inhibition mechanism and the suggestion of a suitable electrical model to explain the behavior of the alloys under different conditions. The investigation of the electrochemical behavior of alloys before and after the corrosion inhibition processes has shown that some amino acids like lysine have promising corrosion inhibition efficiency at very low concentrations. A model for the electrode/electrolyte interface during the corrosion inhibition processes was suggested and the validity of the model for the explanation of the corrosion inhibition phenomena was discussed.     

Corrosion inhibition of mild steel in neutral aqueous solution by new triazole derivatives

Selected triazole derivatives have been synthesised and evaluated as corrosion inhibitors for mild steel in natural aqueous environment by weight loss, potentiodynamic polarisation and ac impedance methods. All the condensed products showed good inhibition efficiency (IE). The effect of changing functional groups of some triazole derivatives on their inhibition efficiency was also reported using weight loss and potentiodynamic technique. 3-Salicylalidene amino-1,2,4-triazole phosphonate (SATP) was found to be the best corrosion inhibitor compare to the other compounds. Surface analysis was carried out to establish the mechanism of corrosion inhibition of mild steel in neutral aqueous media.     

Polymeric Corrosion Inhibitors for Iron and Its Alloys: A Review

Several works have been reported on the corrosion inhibition of different metals in various corrosive environments. Initially attention was centered on organic compounds but later focused on green inhibitors. Green inhibitors include nontoxic, eco-friendly polymers and natural inhibitors. In recent years, there has been increased emphasis on applications of polymers, copolymers, grafted polymers, and polymer composites as green corrosion inhibitors. The prime controlling factors influencing the corrosion inhibitive performance of polymeric compounds on the corrosion of metals in various corrosive environments are discussed in this review. The superior performance of a polymeric corrosion inhibitor is due to its larger size and greater number of functional anchoring groups. Through the anchoring groups the polymers easily get adsorbed on the metal surface and cover considerably more surface than the corresponding monomers. The main factors influencing the corrosion mitigating properties of the polymers are molecular size, weight, composition, and nature of the anchoring groups. The solution pH, concentration, exposure time, and temperature also find their role in inhibition performance. In this review, we have tried to cover various types of polymeric corrosion inhibitors for iron and its alloys.     

Inhibition of mild steel corrosion in hydrochloric acid solution by triazole derivatives: Part I. Polarization and EIS studies

A comparative study of 5-amino-1,2,4-triazole (5-ATA), 5-amino-3-mercapto-1,2,4-triazole (5-AMT), 5-amino-3-methylthio-1,2,4-triazole (5-AMeTT) and 1-amino-3-methylthio-1,2,4-triazole (1-AMeTT) as inhibitors for mild steel corrosion in 0.1 M HCl solution at 20 °C was carried out. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were applied to study the metal corrosion behaviour in the absence and presence of different concentrations of these inhibitors under the influence of various experimental conditions. Measurements of open circuit potential (OCP) as a function of time till reaching the steady-state potentials (E_st) were also established. The studies have shown that 5-AMT was the most efficient inhibitor reaching values of inhibition efficiency (IE%) up to 96% at a concentration of 10⁻³ M. Polarization curves showed that the four studied compounds act as mixed inhibitors. The potential of zero charge (PZC) of mild steel was determined in 0.1 M HCl in the absence and presence of the studied inhibitors. The effect of chemical structure of the four tested inhibitors was discussed. Results obtained from OCP versus time, polarization and impedance measurements are in good agreement.     

Enhancing of Corrosion Inhibition and the Biocidal Effect of Phosphonium Surfactant Compounds for Oil Field Equipment

It is well known that tetra hydroxymethyl phosphonium sulfate (THPS) is commonly used in oil fields as a biocide for sulfate-reducing bacteria (SRB), but it has low corrosion inhibition. In this study, four phosphonium surfactant compounds were synthesized via a coupling reaction between THPS and different fatty acids namely: decanoic, dodecanoic, palmitic and stearic acids to produce the corresponding surfactants. The chemical structure of the synthesized surfactants was confirmed using FTIR and ¹H-NMR spectroscopy. The surface activity of the prepared compounds was determined by surface tension measurements. The critical micelle concentration (CMC) of each surfactant compound was determined. The corrosion inhibition of the synthesized compounds on carbon steel in 0.5 M HCl was studied by weight loss measurements, potentiodynamic and electrochemical impedance spectroscopy. The effect of the inhibitor concentration and hydrophobic chain length on the their efficiency was also studied. It was found that the CMC of each compound depends on its chemical structure. It was also found that the corrosion inhibition efficiency depends on both of concentration and molecular structure of the inhibitors. Polarization curves revealed that the inhibitors used represent mixed-type inhibitors, which hinder the cathodic and anodic parts of the corrosion reaction in acidic media. Adsorption of used inhibitors leads to a reduction in the double layer capacitance and an increase in the charge transfer resistance. Also the biocidal effect of these compounds was enhanced.     

国外有机类铜缓蚀剂综述

随着金属铜及其合金在各领域的应用越来越广泛，其腐蚀与防护问题日益受到重视，而在腐蚀介质中添加缓蚀剂是解决这一问题的一个简单实用的方法。作者综述了近年来国外几种新型有机铜缓蚀剂，包括唑类、喹啉类、嘧啶类等物质，从缓蚀性能、环境保护方面对其进行了比较，介绍了不同介质中缓蚀剂的选用情况，阐述了缓蚀剂的作用机理，并展望了缓蚀剂的研究和发展方向。     

Novel Amide-Based Cationic Surfactants as Efficient Corrosion Inhibitors for Carbon Steel in HCl and H2SO4 media

A variety of surface active compounds were synthesized by the quaternization of some straight chain amide derivatives with triethylamine or pyridine. Their structure FT-IR and ¹H-NMR spectra were recorded. In addition their physical properties and corrosion prevention efficiencies were investigated. All compounds were tested with steel coupons in acidic media by the gravimetric method. As acidic media 1.5 M HCl and 1.5 M H₂SO₄ were used and the corrosion inhibition tests fulfilled at room temperature for 24 h. Almost all prepared cationic surfactants showed efficient inhibition around their critical micelle concentrations. The effects of HCl concentration on corrosion inhibition of some synthesized compounds were also investigated. The corrosion tests were supported by contact angle measurements.     

Synthesis and Evaluation of 4-Diethyl Amino Benzaldehyde Schiff Base Cationic Amphiphiles as Corrosion Inhibitors for Carbon Steel in Different Acidic Media

A novel series of cationic surfactants containing Schiff base groups were synthesized by condensation of fatty amines namely: dodecyl, tetradecyl, hexadecyl and octadecyl amine and 4-diethyl aminobenzaldehyde. The chemical structures of these surfactants were confirmed using elemental analysis, FTIR spectra, ¹H-NMR and atomic absorption spectroscopy. Surface properties of the synthesized compounds were determined using surface tension techniques. The results of the surface tension measurements showed good surface behaviors of these compounds in their aqueous solutions. The surface activities were found to be greatly influenced by the chemical structures of the synthesized compounds. The synthesized cationic Schiff bases were evaluated as corrosion inhibitors for carbon steel in different acidic media (HCl and H₂SO₄) at different doses (400, 200, 100, 50, 25 ppm). The corrosion inhibition efficiencies of these inhibitors were calculated using the corrosion rates of the carbon steel in the studied media and found in the acceptable range of the commercially used inhibitors. Also the chemical structure of these inhibitors was found of great influence on their inhibiting efficiency.     

Synthesis of undecanoic acid phenylamides as corrosion inhibitors

Non‐substituted or mono‐substituted 11‐cyano or 11‐thiocyanato undecanoic acid phenylamide derivatives were synthesized and characterized with their FT‐IR and ¹H‐NMR spectra. Thereafter, their corrosion prevention efficiencies were investigated. All compounds were tested with steel coupons in acidic medium by a gravimetric method. Acidic tests were done with a medium concentration of 2 M HCl for 5 h at variable temperatures and inhibitor concentrations. The corrosion prevention efficiencies of the inhibitors were compared according to their chemical structures and the corrosion inhibition mechanism was also discussed. The synthesized compounds showed promising corrosion inhibition efficiencies under the outlined test conditions. Best inhibitions were obtained at 27°C and 100 ppm concentration of corrosion inhibitors.     

Synthesis of Bis[<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-(alkylamideethyl)ethyl] Triethylenediamine Bromide Surfactants and Their Oilfield Application Investigation

Bis[N,N′-(alkylamideethyl)ethyl] triethylenediamine surfactants are quaternary ammonium salt Gemini surfactants with amide, which are synthesized from fatty acid (dodecanoic, hexadecanoic, tetradecanoic and octadecanoic) methyl esters, triethylene tetramine and ethyl bromide. The chemical structures of the prepared compounds were characterized by elemental analysis, FTIR and ¹H-NMR spectra, melting point and Krafft point. Several properties of the synthesized surfactants were studied including surface tension, critical micelle concentration, interfacial tension, emulsification power, salt effect, corrosion inhibition efficiency and biological activity. The results show that the surface activity, critical micelle concentration and interfacial activity are correlated to their chemical structures. The emulsification power measurements of these surfactants show their low emulsifying tendency towards Tazhong’s crude oil from Tarim Oilfield. The synthesized surfactants also exhibit high biocidal activity towards Gram-positive and Gram-negative bacteria and fungi. This activity increases with the increase of alkyl chain length. The corrosion measurement of these surfactants in acidic media with a weight loss technique show good protection of mild steel alloys against acidic environments. These properties suggest that the synthesized compounds have potential for application in the oilfield area.     

Synthesis of Quaternary,Long-Chain N-Alkyl Amides and Their Corrosion Inhibition in Acidic Media

New cationic surfactants were synthesized by the quaternization of a number of straight-chain amide derivatives with triethylamine or pyridine. The corrosion inhibition tests of the surface-active compounds were performed at room temperature for 24 h on carbon steel coupons in acidic media using the gravimetric method. The acidic media used were 1.5 M HCl and 1.5 M H₂SO₄. Almost all of the synthesized cationic surfactants showed efficient inhibition of corrosion in the test. To establish the inhibition efficiencies of the inhibitors, surface characterization studies (contact angle measurements, SEM analysis and optical profilometer images) of the metal coupons used were performed.     

Synthesis and Evaluation of Some Triazole Derivatives as Corrosion Inhibitors and Biocides

Three compounds namely; 5-(phenyl)-4H-1,2,4-triazole-3-thiol, 3-(decylthio)-5-phenyl-1H-1,2,4-triazole and 3-(benzylthio)-5-phenyl-1H-1,2,4-triazole) were synthesized. The chemical structure of the prepared compounds was confirmed using FTIR and ¹H-NMR analysis. The compounds were tested as corrosion inhibitors against the corrosion of carbon steel in 1 M HCl using weight loss, polarization and electrochemical impedance methods. The results revealed that these compounds have significant inhibiting effects on the corrosion of carbon steel. Polarization studies showed that the compounds act as mixed-type inhibitors which retard the anodic and the cathodic reactions with a predominant effect towards the cathodic reaction. The prepared compounds were evaluated as antimicrobial agents against sulfate-reducing bacteria using the serial dilution method, which showed good biocidal action.     

Novel Hybrid 1,2,4- and 1,2,3-Triazoles Targeting Mycobacterium Tuberculosis Enoyl Acyl Carrier Protein Reductase (InhA): Design,Synthesis, and Molecular Docking

Tuberculosis (TB) caused by Mycobacterium tuberculosis is still a serious public health concern around the world. More treatment strategies or more specific molecular targets have been sought by researchers. One of the most important targets is M. tuberculosis’ enoyl-acyl carrier protein reductase InhA which is considered a promising, well-studied target for anti-tuberculosis medication development. Our team has made it a goal to find new lead structures that could be useful in the creation of new antitubercular drugs. In this study, a new class of 1,2,3- and 1,2,4-triazole hybrid compounds was prepared. Click synthesis was used to afford 1,2,3-triazoles scaffold linked to 1,2,4-triazole by fixable mercaptomethylene linker. The new prepared compounds have been characterized by different spectroscopic tools. The designed compounds were tested in vitro against the InhA enzyme. At 10 nM, the inhibitors 5b, 5c, 7c, 7d, 7e, and 7f successfully and totally (100%) inhibited the InhA enzyme. The IC₅₀ values were calculated using different concentrations. With IC₅₀ values of 0.074 and 0.13 nM, 7c and 7e were the most promising InhA inhibitors. Furthermore, a molecular docking investigation was carried out to support antitubercular activity as well as to analyze the binding manner of the screened compounds with the target InhA enzyme’s binding site.     

Preparation,hydrogen bonding and properties of polyurethane elastomers with 1,2,3-triazole units by click chemistry

Two kinds of diols containing 1,2,3-triazole units were synthesized through the azide-alkyne cycloaddition reaction between propargyl alcohol and 1,4-diazidobutane. One of the diols, (butane-1,4/1,5-diylbis[1H-1,2,3-triazole-1,4/1,5-diyl])dimethanol (BDTDO-1), containing 1,4/1,5-disubstituted 1,2,3-triazole regioisomers, was directly prepared under thermal condition without Cu(I) catalyst. The other diol, (butane-1,4-diylbis[1H-1,2,3-triazole-1,4-diyl])dimethanol (BDTDO-2), containing 1,4-disubstituted 1,2,3-triazoles, was prepared by Cu(I) catalyzed click chemistry. Then, two kinds of 1,2,3-triazole modified polyurethane elastomers (PUEs) were prepared from the reaction of 4,4′-methylenebis(phenyl isocyanate) and poly(tetramethylene ether) glycol, with BDTDO-1 or BDTDO-2 as the chain extender (CE). It was found that the introduction of 1,2,3-triazoles and their substitution positions had significant influences on the hydrogen bonding, thermal and mechanical properties of PUEs. Compared with the PUE prepared from 1,4-butanediol as the CE, the PUE containing symmetric 1,4-disubstituted 1,2,3-triazoles units in the main chains shows higher values of hydrogen bonding, physical crosslinking density, Young's modulus, tensile strength and melting temperature, while lower glass transition temperature, resulting from the rigid structure and the ability to form more hydrogen bonds. However, the introduction of asymmetric 1,4/1,5-disubstituted 1,2,3-triazole moieties decreases the values of hydrogen bonding, thermal and mechanical properties of PUE appreciably due to the destruction of the ordered structure of the hard segments.     

Inhibitive effects of isatin,thiosemicarbazide and isatin-3-(3-thiosemicarbazone) on the corrosion of aluminium alloys in nitric acid

The inhibitive efficiencies of isatin, thiosemicarbazide and their condensation product, i.e. isatin-3-(3-thiosemicarbazone) are studied at different concentrations in relation to corrosion of aluminium alloys (1060,1100, 3003) in 20% nitric acid at 30, 40 and 50° C using the weight loss method. Polarization experiments have been performed at 0.05, 0.2 and 0.3% concentrations of the inhibitors at 30° C. It is found that isatin-3-(3-thiosemicarbazone) is a more effective inhibitor as compared to the parent compounds for the three alloys at all the experimental temperatures. The effectiveness of the inhibitors increases with increase in temperature from 30° C to 50° C. The inhibitors are found to retard the corrosion by predominantly acting on local cathodes although they are also partially effective on the anodes. The critical current density for the passivation of aluminium decreases almost in the same order as the inhibition efficiency of the inhibitors increases.     

Synergistic Inhibition Effect of Chitosan and L-Cysteine for the Protection of Copper-Based Alloys against Atmospheric Chloride-Induced Indoor Corrosion

The protection of metals from atmospheric corrosion is a task of primary importance for many applications and many different products have been used, sometimes being toxic and harmful for health and the environment. In order to overcome drawbacks due to toxicity of the corrosion inhibitors and harmful organic solvents and to ensure long-lasting protection, new organic compounds have been proposed and their corrosion inhibition properties have been investigated. In this work, we describe the use of a new environment-friendly anticorrosive coating that takes advantage of the synergism between an eco-friendly bio-polymer matrix and an amino acid. The corrosion inhibition of a largely used Copper-based (Cu-based) alloy against the chloride-induced indoor atmospheric attack was studied using chitosan (CH) as a biopolymer and l-Cysteine (Cy) as an amino acid. To evaluate the protective efficacy of the coatings, tailored accelerated corrosion tests were carried out on bare and coated Cu-based alloys, further, the nature of the protective film formed on the Cu-based alloy surface was analyzed by Fourier-transformed infrared spectroscopy (FTIR) while the surface modifications due to the corrosion treatments were investigated by optical microscopy (OM). The evaluation tests reveal that the Chitosan/l-Cysteine (CH/Cy) coatings exhibit good anti-corrosion properties against chloride attack whose efficiency increases with a minimum amount of Cy of 0.25 mg/mL.     

Inhibiting effects of some synthesized organic compound on the corrosion of St-3 in 0.1N H2SO4 solution

The inhibiting properties of two synthesized metals (alkyl)-2-hydroxy benzene sulfonate compounds have been studied on the corrosion of steel (St-3) in aerated 0.1N H₂SO₄ solutions by potentiodynamic polarization (dc) technique and electrochemical impedance spectroscopy (ac). The polarization curves indicate that the inhibitors are mixed-type. The impedance increases with inhibitors concentration. Low difference in inhibition efficiencies of two compounds for the corrosion of St-3 steel could be explained by high similarities of their structures. Results obtained by both electrochemical methods are in relatively good agreement.     

Electrochemical and theoretical studies of thienyl-substituted amino triazoles on corrosion inhibition of copper in 0.5 M H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

2,5-Bis(2-thienyl)-4-amino-1,2,4-triazole (2-TAT) and 2,5-bis(3-thienyl)-4-amino-1,2,4-triazole (3-TAT) have been studied as inhibitors for the corrosion of copper in 0.5 M H₂SO₄ using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The inhibition efficiency of the triazole compounds increases with increasing concentration, and the effect of 3-TAT is better than that of 2-TAT with the same concentration. Potentiodynamic polarization measurements indicate the triazole compounds act as mixed type inhibitors in 0.5 M H₂SO₄. The adsorption of the triazole compounds is found to obey the Langmuir adsorption isotherm. High significant correlations for the triazole compounds are obtained between inhibition efficiency and quantum chemical parameters (R = 0.975) using the quantitative structure–activity relationship (QSAR) method.