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Highlights • Halogen-substituted thiazole were investigated as mild steel inhibitor in H 2 SO 4. • Cl- and Br- substituted thiazoles exhibit high inhibition efficiencies at 60 °C. • Reaction mechanism at high temperature were revealed by theoretical calculations. Abstract The inhibitory effects of three halogen-substituted thiazole derivatives named 2-amino-4-(4-fluorophenyl)-thiazole (FPT), 2-amino-4-(4-chlorophenyl)-thiazole (CPT) and 2-amino-(4-bromophenyl)-thiazole (BPT) on mild steel corrosion were investigated in 0.5 M H 2 SO 4 from 30 °C to 60 °C. Electrochemical measurements demonstrated that these thiazoles can effectively inhibit the corrosion of mild steel in 0.5 M H 2 SO 4 solution at 30 °C. With the increase of temperature, the inhibition efficiency (η) of FPT at 60 °C reduced to 22.62% while those of CPT and BPT under the same temperature were nearly unchanged, which were as high as 95.16% and 95.45%, respectively. The adsorptions of three thiazoles on the surface of mild steel were all found to adhere to Langmuir adsorption isotherm at 30 °C while only CPT and BPT obeyed at 60 °C. Quantum calculations results indicated that CPT and BPT had the better adsorption ability on mild steel than FPT. Molecular dynamic stimulations were taken out to investigate the adsorption configurations of three thiazoles on the surface of Fe (0 0 1) at 30 °C and 60 °C, and the results implied that the binding energy of protonated BPT and CPT were nearly unchanged at studied temperatures while that of protonated FPT apparently became lower at 60 °C. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Highlights • Adsorption of protonated thaizole molecules and anions on the iron (0 0 1) surface was firstly investigated with MD simulations. • The optimal inhibition performance of methoxy-substituted in acidic solutions for mild steel was as high as 95% and it was much better than unsubstituted thiazoles. • UV-vis spectra measurements were used to establish direct correlation of experimental data with theoretical calculations. • Introduction of electron-donating group indeed enhance the inhibition ability. Abstract The inhibitory effects of 2-amino-4-(4-methoxyphenyl)-thiazole (MPT) on mild steel corrosion were evaluated in 0.5 M H 2 SO 4 and 1 M HCl solutions, respectively. From the analysis of potentiodynamic polarization curves and electrochemical impedance spectroscopy, MPT can effectively inhibit the corrosion of mild steel in acidic solutions. Under the optimal conditions, the inhibition efficiency (η) was as high as 95% in 0.5 M H 2 SO 4 solution. The inhibition property of MPT was much better than that of the reported corrosion inhibitor 2-amino-4-phenylthiazole (APT). Polarization curves also demonstrated that MPT mainly inhibited the anodic corrosion of mild steel in HCl solution and the cathodic corrosion in H 2 SO 4 solution, respectively. The adsorption of MPT on the surface of mild steel was found to obey Langmuir adsorption isotherm in both acid solutions. Quantum calculations suggest that the addition of electron donor group (−OCH 3) endowed the molecule better adsorption ability on mild steel surface. The interaction between protonated MPT and anions on Fe (0 0 1) surface was firstly investigated using molecular dynamic stimulations, and the results showed that with the adsorption of sulfate ions, MPTH+ had a superior binding energy on the surface of Fe. The investigation of UV–vis spectrum demonstrated the direct correlation of the experimental data and the theoretical calculations. [ABSTRACT FROM AUTHOR]

Two novel Schiff bases, (E)‐N‐(4‐hydroxy‐3‐methoxybenzylidene)lysine (1) and (E)‐N‐(4‐hydroxy‐3‐methoxybenzylidene)arginine (2) were synthesized by using natural products of amino acid and vanilline, and their inhibitive effect on the corrosion of mild steel in 0.5 mol⋅L−1 HCl solution was evaluated by various experimental methods such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves, scanning electron microscope (SEM), atomic force microscopy (AFM) and X‐ray photoelectron spectroscopy (XPS). Moreover, quantum chemical calculations and molecular dynamics simulations were used to theoretically explore the internal relation between inhibitory efficiency and molecular structure. The results of EIS show the polarization resistance of mild steel is increased from 6.592 Ω⋅cm2 to 36.46 Ω⋅cm2 and 74.78 Ω⋅cm2 in the presence of 1 and 2, respectively. Tafel curves indicate HMBL and HMBA act as good inhibitors for iron corrosion in hydrochloric acid and that 2 has the better performance than 1. XPS analysis confirms the adsorption of inhibitor molecules on iron surface by forming inhibitor‐Fe complex, which is well fitted by Langmuir model. The corrosion of mild steel in 0.5 molL−1 HCl solutions is inhibited by novel Sciff bases synthesized from amino acid and vanilline in green way. Esperimental results and theoretical studies indicate 1 and 2 act as mixed‐type inhibitors with dominant cathodic effect and that the better performance of 2 on corrosion inhibition may be due to the two extra N atoms in molecular structure. [ABSTRACT FROM AUTHOR]

A new imidazoline compound, 2-(2-tribromomethyl-4,5-dihydro-imidazol-1-yl)-ethylamine (3-IM) was synthesized and its inhibitory effect on the corrosion of mild steel in 0.5 M HCl solution was examined by weight loss, potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). The experimental results show that 3-IM behaves as a mixed-type inhibitor and the inhibition efficiency increases with the increasing compound concentrations. The adsorption actions of 3-IM molecules are well fitted by Langmuir isotherm, while the protection property of the adsorptive layer decreases as the temperature increases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gum arabic was utilized as a green stabilizer to prepare water-soluble sulfur dots. • Corrosion inhibition reached the maximum value of 96.5% at 250 mg/L. • Antibacterial efficiency against Bacillus subtilis was up to 99.35% at 250 mg/L. • Fluorescent tracking of water treatment agents was realized. • Facilitated the development of a next generation of multifunction inhibitors agent. In this study, sulfur dots (GA-SDs) synthesized by using Gum Arabic (GA) as a green stabilizer were used as corrosion inhibitors and their inhibition effect for Q235 steel in 3.5- wt% NaCl solution was investigated by weight loss, electrochemical tests, and surface and interface analysis. The results revealed that the inhibition efficiency reached the maximum value of 96.5% at 250 mg/L and the water-soluble GA-SDs were able to adhere to the iron surface through the diffusion and agglomeration effect. The unique antibacterial activities demonstrated a 99.35% inhibition efficiency at 250 mg/L. Moreover, the optical properties endowed the inhibitors with the fluorescence tracing function, which is an effective approach to detecting the residual quantity of water treatment agents. This work may facilitate the development of the next generation of multifunction water treatment agents in industrial circulating water systems. [ABSTRACT FROM AUTHOR]

Konjac glucomannan (KGM) was modified with amino acids to synthesize polysaccharide esters (KGMA and KGMH) which were evaluated as corrosion inhibitor for mild steel in 0.5 M HCl solution by weight loss tests, Tafel curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The synthetic polymers were found to have the lower water absorbency and the higher water solubility than KGM. Gravimetric measurements showed the maximum efficiencies of KGMA and KGMH for decreasing the corrosion rate of metal at 2000 ppm are up to 89.9% and 92.4%, respectively. Polarization curves indicated polysaccharide esters could retard both hydrogen evolution reaction and metal dissolution reaction and that the inhibitory effect was concentration dependent. Besides, EIS studies demonstrated the corrosion resistance of mild steel in hydrochloric acid was enhanced by polymer additives. The observations on mild steel surface by SEM suggested the metallic substrate obtained good protection against corrosion in inhibitor-containing HCl solution. The adsorptive behavior of polymer molecules including physisorption and chemisorption obeyed Langmuir isotherm and UV–vis spectra revealed the formation of inhibitor-ion complex. The better performance of KGMH on corrosion inhibition was attributed to the easier transfer of π-electron or n -electron, which was confirmed by quantum chemical calculations. [ABSTRACT FROM AUTHOR]

The deposition of CaCO 3 scale in circulating cooling water on metal surface is a major concern in industry. This paper focuses on the feasibility of electrochemical methods to study the scale inhibition performance of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), Polyacrylic Acid (PAA), including linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS). In addition, the coverage, morphology and structure of deposited CaCO 3 crystal on titanium alloy surface in the absence and presence of inhibitors were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A new method for calculating the efficiency of scale inhibitors was proposed so that it can be calculated by using the change in residual current density (i r). In order to prove the feasibility and accuracy of such method, the efficiencies of inhibitors were evaluated using i r and charge transfer resistance (R ct), respectively. In addition, molecular dynamics (MD) simulations were performed to evaluate the interaction between the scale inhibitor molecule and the CaCO 3 crystal. The experimental results show that both the residual current density obtained by chronoamperometry and the charge transfer resistance obtained by electrochemical impedance spectroscopy can be used to evaluate the efficiency of scale inhibitors, and there is high consistency from the calculation results. It is also confirmed by X-ray diffraction and scanning electron microscopy studies that the presence of inhibitor reduces the surface coverage of CaCO 3 at metal electrode and that the crystal structure of CaCO 3 is transformed from the original aragonite into the most unstable vaterite. The best inhibition efficiency of PBTCA for CaCO 3 deposit is confirmed by the results of MD simulations. [ABSTRACT FROM AUTHOR]

Two novel imidazoline derivatives, 2-(2-trifluoromethyl-4,5-dihydro-imidazol-1-yl)-ethylamine (1-IM) and 2-(2-trichloromethyl-4,5-dihydro-imidazol-1-yl)-ethylamine (2-IM), have been investigated as corrosion inhibitors for mild steel in 0.5 M HCl solution by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. The surface morphology of sample was presented through scanning electron microscope (SEM) and the inhibition mechanism was elucidated by measuring the potential of zero charge ( E pzc ) at the solid/liquid interface. Results of theoretical calculation confirm that the chloride-substituted compound shows better inhibitive performance than the fluoride-substituted one. [ABSTRACT FROM AUTHOR]

Highlights: [•] The studied inhibitors contain both pyridine ring and Schiff’s base structure. [•] The inhibitors show good inhibitive properties for mild steel in HCl. [•] The inhibitors adsorb on mild steel surface both physically and chemically. [•] The PZC measurements show the mild steel surface was positively charged. [Copyright &y& Elsevier]

Abstract: The efficiency, as steel corrosion inhibitors in 0.5M H2SO4, of two thiadiazole derivatives, 2-amino-5-(3-pyridyl)-1,3,4-thiadiazole (3-APTD) and 2-amino-5-(4-pyridyl)-1,3,4-thiadiazole (4-APTD), was investigated by polarization and electrochemical impedance spectroscopy. The protection efficiency increases with increasing inhibitors concentration, but the temperature has hardly effect on the inhibition efficiency of APTD. The adsorption of APTD on iron surface obeys the Langmuir isotherm. The experimental results show that the inhibition efficiency of 4-APTD is higher than that of 3-APTD, and the molecular dynamics (MD) simulations show that the adsorption of 4-APTD on iron surface has the higher binding energy than that of 3-APTD. [Copyright &y& Elsevier]