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The corrosion inhibition performance of L(-)- Cystine on copper alloy immersed in 2 M HNO3 solution is investigated using weight loss, potentiodynamic polarisation, electrochemical impedance spectroscopy, and scanning electron microscopy. Potentiodynamic polarization measurements confirmed that L(-)-Cystine behaved as mixed-type inhibitor. The highest corrosion inhibition efficiency was 98.99% at 298 K and decreased with increasing temperature. The Nyquist plots displayed an increase in the capacitive loops with increasing the concentration of the inhibitor. The mechanism of inhibition obeys Langmuir isotherm. SEM images confirm the adsorption of L(-)-Cystine on the surface of the cooper alloy [ABSTRACT FROM AUTHOR]

The inhibition of (3ar,6ar)-3a,6a-di-p-tolyltetrahydroimidazo[4,5-d]imidazole-2,5(1 h,3h)-dithione (TTHIIDT) for carbon steel was full characterized in a 1 M hydrochloride acid environment at various inhibitor concentrations and temperatures by the gravimetric, electrochemical, surface and quantum chemical analyses. The obtained results confirmed that the inhibition efficiency of TTHIIDT was over 95–97% and nearly stable in the rise of temperature and concentration; TTHIIDT was mixed type inhibitor and effectively influenced both anodic and cathodic corrosion reactions; a protective hydrophobic thin layer of this inhibitor on the carbon steel surface is more stable and non soluble in 1 M HCl medium; this inhibitor adsorbed endothermically on the carbon steel surface by the chemical and physical adsorption processes. The quantum chemical calculations supported the experimental results and showed that the inhibition efficiency is depends on the structure of inhibitor. [ABSTRACT FROM AUTHOR]

• DM drug was introduced as a novel corrosion inhibitor. • Polarization measurements signify that DM drug acted as a mixed mode inhibitor. • Adsorption mode best reflect in Langmuir isotherm. • MD-simulation reveals the vital role of active sites of DM molecule in their adsorption. • ANFIS best predicted the interactive effects between the input and output response. In this research, the effect of Dexamethasone drug (DM) on mild steel corrosion in 2 M HCl was analyzed using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and MD-simulation. In addition, Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), Energy dispersive x-ray spectroscopy (EDX), and atomic force microscopy (AFM) were employed to inspect the mild steel surface in the blank and inhibited medium. For the optimization tool, adaptive neuro-fuzzy inference system (ANFIS) model was developed to predict the inhibition efficiency. The experimental data was categorized into two different sections for training and testing the ANFIS model. The developed model aimed to evaluate the fitness between the experimental and predicted values. From the results generated, optimum value (IE%) of DM was recorded as 80%, 81% and 83% at concentration of 0.4 g/L for weight loss, EIS and PDP respectively. Potentiodynamic polarization results reveal that Dexamethasone functions as a mixed-type inhibitor, whereas studies of EIS show that the inhibition mechanism is by the transfer of charges. Mild steel surface examination confirmed the presence of a protective adsorbed film on the mild steel surface. Thermodynamic parameters obtained imply that Dexamethasone is adsorbed on the steel surface by a physiochemical process and obeys Langmuir adsorption isotherm. Also the MD-simulation results evidenced that DM forms a metallic surface adsorbed film on the steel surface. From the ANFIS model, the sensitivity analysis shows that time and inhibitor concentration were the most important input variable while other input variables could not be neglected. ANFIS model coefficient of determination (R 2 0.993) was found between the observed and predicted values. ANFIS model gave optimum prediction (80%) with high degree accuracy and robustness. The outcomes of this investigation provide more information, simulation, and prediction about inhibition of metal corrosion. [ABSTRACT FROM AUTHOR]

The anticorrosive potential of Ficus hispida leaf extract (FHLE) as a corrosion inhibitor in 1 M HCl was investigated using weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Stigmasterol as the major constituent of F. hispida was confirmed by Gas Chromatography–Mass Spectrometry (GC–MS). Inhibition efficiency of 90% was achieved with 250 ppm of FHLE at 308 K. Temperature studies revealed an increase in inhibition efficiency with decrease in temperature and activation energies increased in the presence of the extract. Cathodic and anodic polarization curves revealed that FHLE acts as mixed type inhibitor, but cathodic effect was more pronounced. Impedance diagrams showed that increasing FHLE concentration, increased charge transfer resistance and decreased double layer capacitance. The adsorption of FHLE on mild steel surface obeyed Langmuir adsorption isotherm. The morphology of the surface was examined by scanning electron microscopy (SEM) and the surface composition was evaluated using energy-dispersive X-ray (EDX) spectroscopy to verify the presence of inhibitor on the mild steel surface. The adsorbed film on the mild steel surface containing the FHLE inhibitor was also characterized by diffuse reflectance Fourier transform infrared spectroscopy (DRFT-IR) and X-ray diffraction (XRD) studies. [ABSTRACT FROM AUTHOR]

The study examined the effectiveness of Berlinia grandiflora (BEG) and cashew (CEG) exudate gums in protecting mild steel from corrosion in 1 M HCl solution using weight loss, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP). The corrosion products were analyzed using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDX), atomic force microscopy (AFM), Fourier Transformed Infrared spectroscopy (FTIR), and optical profilometry. Results indicate that the exudate gums are effective against the corrosion of mild steel in an HCl solution. The EIS results reveal that the charge transfer resistance of the metal in the acid solution increased from 82.2 Ω cm2 to 1074.0 Ω cm2 and 325.1 Ω cm2 in the presence of 1000 ppm BEG and CEG, respectively corresponding to inhibition efficiency (η) of 92% and 75% at 25 °C. The Gum's performance depends on immersion time and temperature. It improves with an increase in immersion time up to 48 h but thereafter slightly diminishes. The η of 1000 ppm of BEG and CEG after 48 h of immersion is 76% and 67%, respectively at 30 °C. With a temperature rise, η of BEG appreciates to 80% while that of CEG depreciates to 57% at 60 °C after 24 h of immersion. Both BEG and CEG retard the metal corrosion through an adsorptive mechanism whereby it blocks the active corrosion reaction sites on the surface. The adsorption was confirmed by SEM/EDX, AFM, UV–vis, and FTIR. BEG and CEG are promising and sustainable sources for metal corrosion inhibitor formulations. [Display omitted] • BEG and CEG were assessed as sustainable corrosion inhibitors for mild steel in acid medium. • BEG and CEG are effective in protecting mild steel. Inhibition efficiency increases with concentration. • BEG extract outperformed CEG under all testing conditions. • The exudate gums exhibited features peculiar with mixed-type inhibitors. • The inhibition performance of BEG increased with temperature while CEG decreased. [ABSTRACT FROM AUTHOR]

[Display omitted] • Doxorubicin drug acted as a mixed-type corrosion inhibitor. • Surface analysis via SEM and XPS evidenced the presence of inhibitor barrier film. • The best ML prediction was made using complete FCM-ANFIS model with high degree of accuracy. • The experimental results were supported by DFT/MDS. In this work, Doxorubicin drug was used as mild steel corrosion inhibitor in 0.5 M H 2 SO 4 solution. Herein, standard techniques like gravimetric, electrochemical measurement, density functional theory via DFT/ molecular dynamic simulation (MDS), Scanning electron microscopic (SEM), were used for proper evaluation of Doxorubicin drug as anticorrosive agent. According to the experimental findings, Doxorubicin drug significantly inhibits mild steel corrosion, and its effectiveness increases with an increase in the drug concentration. Maximum inhibition efficiency at 100 ppm was 93.3 %, 91.3 % and 96.8 % for electrochemical impedance (EIS), polarization test (PDP) and gravimetric techniques respectively. The electrochemical study indicates that Doxorubicin is a mixed-type inhibitor. Close scrutiny of the corroded and inhibited metals evidenced that Doxorubicin drug produced a better and more uniform coating on the surface of mild steel. The molecular structure of the drug and its contribution to the inhibition mechanism was further understood using simulations based on density functional theory (DFT) and molecular dynamics simulation (MDS). In addition, artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) were used to predict and model the interactive effects affecting the response. Also, statistical parameters like coefficient of determination (R2), root mean square error (RMSE), mean absolute percentage error (MAPE), and mean absolute deviation (MAD) were used to assess the models' performance. The results demonstrate that the FCM-clustered ANFIS model with 15 clusters perform better than ANN model with RMSE, MAD, MAPE, and R2values of 0.978, 0.642, 4.823, and 0.9925 at the testing phase, and 0.6435, 0.4248, 2.8151, and 0.9998 at the training phase respectively. The best prediction was made using complete FCM-ANFIS model, which had accuracy of 98.4 %. Hence, a robust system prediction can be achieved via ANN and ANFIS algorithms to predict corrosion inhibition of mild steel in acidic environment using drug based corrosion inhibitors. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Two benzaldehyde thiosemicarbazone derivatives show high inhibition efficiency. • These compounds acted as mixed type inhibitors. • The adsorption of these inhibitors follows Langmuir adsorption isotherm. • Results of theoretical calculations were in accordance with weight loss and electrochemical measurements. Abstract Two benzaldehyde thiosemicarbazone derivatives namely 3-methoxy,4-hydroxyl-benzaldehyde thiosemicarbazone (MHBT) and 2-hydroxyl,3-methoxy-benzaldehyde thiosemicarbazone (HMBT) were synthesized and their inhibition behavior for mild steel in 1.0 M HCl solution was investigated using gravimetric measurements and electrochemical tests. Weight loss measurements suggested that these two compounds acted as efficient inhibitors for mild steel in 1.0 M HCl solution and the inhibition efficiency reached a maximum value of 96.1% and 95.7% for HMBT and MHBT, respectively. Potentiodynamic polarization results revealed that both of these two compounds were mixed-type inhibitors. Scanning electron microscopy and energy dispersive spectrum were performed to confirm the presence of benzaldehyde thiosemicarbazone derivatives on mild steel surface. The adsorption of these two inhibitors on mild steel surface in 1.0 M HCl solution follows the Langmuir adsorption isotherm. Correlation between the molecular structure and inhibition property were also discussed using quantum chemical calculations. [ABSTRACT FROM AUTHOR]

Highlights • A novel compound, EBIMOT, containing two biologically active moieties 1,3,4-oxadiazole and benzimidazole, was synthesized. • Its efficacy towards the corrosion prevention of mild steel in 0.5 M HCl using a combined experimental and theoretical approach. • EBIMOT acted as a good corrosion inhibitor for mild steel corrosion in 0.5 M HCl showing an efficiency of 91% at 760 µM and 313 K. • The adsorption phenomenon obeys Langmuir isotherm with negative values of free energy between −20 kJ mol−1 and −40 kJ mol−1. • Inhibition efficiency increases with inhibitor concentration and decreases with temperature. Abstract A new organic compound, 5-((2-ethyl-1Hbenzo[d]imidazol-1-yl)methyl)-1,3,4-oxadiazole-2-thiol (EBIMOT) has been investigated for its efficacy in the corrosion inhibition of mild steel in 0.5 M HCl at three different temperatures by classical weight loss technique, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods. EBIMOT shows high inhibition activity through adsorption and this phenomenon was found to obey Langmuir adsorption isotherm. The kinetic parameters were also derived using the experimental data. The quantum chemical DFT studies were used to correlate the interrelation of inhibition efficiency and molecular structure. [ABSTRACT FROM AUTHOR]

Abstract 2-amino-4-methylbenzothiazole (AMBT) and one of its derivatives (E)-2-methylbenzo[d]thiazol-2-yl)imino-4-methyl) phenol (MBTP) were used as synergistic pair for the protection of mild steel in 0.5 M HCl. The combination of inhibitors, AMBT-MBTP, adsorbs on electrode surface through chemical and physical means. The antagonistic interaction was more pronounced on higher temperature, and an inhibition efficiency of 92% was recorded at 313 K and 93% at 303 K. The formation of protective film of AMBT-MBTP combination is further evidenced by SEM and AFM images. The process of adsorption followed Langmuir isotherm model and corresponding thermodynamic activation parameters were also calculated and discussed. Corrosion inhibition efficiency and the reaction kinetics of synergistic pair were evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and weight loss measurements. H-bonding interaction and resulting enthalpy change and reactivity descriptors were computed for correlating the corrosion inhibition efficiency and molecular structure by B3LYP/6-31G∗ level of Density Functional Theory (DFT). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The biopolymer concentration can affect the anticorrosive property. • Biopolymer concentration of 0.5 g L−1 has the best inhibition efficiency of 58%. • Increasing the temperature can decrease the inhibition efficiency. • The Chryseobacterium indologenes MUT.2 biopolymer can act as a mixed inhibitor. • The biopolymer can make a barrier on metal surface by physisorption. Abstract Corrosion inhibition of Chryseobacterium Indologenes MUT.2 bacterial biopolymer was investigated in different biopolymer concentration (0.2–0.5 gl−1) as well as temperature ranging from 25 to 55 °C in 0.5 M HCl corrosive solution. Electrochemical studies were performed by Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization using Tafel extrapolation technique under different conditions. Results showed that increasing the biopolymer concentration enhanced the inhibition efficiency whereas increasing the temperature decreased the inhibition efficiency. Maximum inhibition efficiency of 58% was obtained in the presence of 0.5 gl−1 biopolymer at room temperature (25 °C). The biopolymer adsorption on metal surface obeyed Langmuir adsorption isotherm. Biopolymer acted as a mix inhibitor and physically adsorbed on metal surface. The biopolymer inhibitor deposition on metal surface has been indicated in Scanning Electron Microscope (SEM) images. Suitable mechanism was proposed for the inhibition process. [ABSTRACT FROM AUTHOR]

• The inhibitor and its reduced version were developed. • The reduced demonstrated excellent performance in static and hydrodynamic conditions. • The corrosion inhibition efficiency increased with increasing concentration in both inhibitors. • The surface adsorption mechanism was identified as Langmuir type. Expanding the use of carbon steel in various industrial operations is always associated with challenges due to many engineering factors in the selection of materials. However, carbon-steel corrosion is a significant challenge in many industries, particularly the oil and gas sector. This study created and employed two novel N 2 O 2 ligands to prevent simple carbon steel from corroding in static and dynamic hydrochloric acid solutions. Corrosion tests were performed in none, 50, 100, and 250 ppm of the new compounds. Therefore, immersion, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests were used to investigate the anti-corrosion effect. In addition, the impact of hydrodynamic conditions on performing the inhibitors was also conducted. The B3LYP (Becke, 3-parameter, Lee–Yang–Parr), HF (Hartree–Fock), M062X approach with 6–31++ G (d,p) basis sets was employed using the Gaussian software to study the inhibitory activities of molecules in the gas and water phases. According to the PDP test, there is a direct correlation between the amount of inhibitor and resistance to corrosion in static conditions, where the reduced ligand was more efficient. The EIS data revealed that, in a 1.0 M HCl solution with an inhibitor concentration of 250 ppm, the ligand and its reduced form enhanced corrosion resistance by 86.38% and 91.43%. Furthermore, these values were found to be 33.46% and 57.77%, in turbulent environment of 500 rpm. The atomic force microscopy (AFM) studies revealed that the ligand and its reduced form decreased surface roughness by 13.61% and 85.37% in static conditions and 59.67% and 61.53% in a hydrodynamic environment in comparison to 1.0 M HCl solution. Additionally, the UV test demonstrated that the amounts of iron corrosion was less severe in H2L2 than in H2L1 and 1.0 M HCl. Under static and dynamic conditions, the samples had lower specific weight changes during the immersion test, indicating that the inhibitory chemicals protected the samples' surfaces. Both compounds followed the Langmuir adsorption process. Furthermore, quantum chemical parameters simulations indicate the compounds' anti-corrosive abilities. [Display omitted] [ABSTRACT FROM AUTHOR]

The anticorrosion effect of 5-hydroxytryptophan (5-HTP) on mild steel (MS) was investigated by gravimetric and electrochemical techniques. Two different concentrations (1 M and 15%) of hydrochloric acid were used to simulate well-acidizing fluid. The results show that 10 × 10 −5 M 5-HTP is 96.1% efficient in 1 M HCl and 78.1% efficient in 15% HCl at 30 °C. The efficiency decreases as the temperature increases, reaching 66.9% and 39.8% in 1 M and 15% HCl, respectively, at 90 °C. When 5-HTP is blended with potassium iodide and glutathione, the efficiency increases to above 88% and 78% in 1 M and 15% HCl, respectively, at 90 °C. Increasing the 5-HTP concentration decreases the double-layer capacitance and increases the charge-transfer resistance. 5-HTP behaves as a mixed‐type corrosion inhibitor with anodic predominance and is spontaneously adsorbed on the steel surface. Physisorption of 5-HTP is best described by the Langmuir adsorption model and is also exothermic with a resultant decrease in the entropy of the bulk solution. The results of SEM/EDAX, FTIR and UV–VIS studies support the hypothesis that a protective film of 5-HTP forms on MS facilitated by O, N and C C functionalities. [ABSTRACT FROM AUTHOR]

The influence of an aromatic hydrazide derivative, 2-(3,4,5-trimethoxybenzylidene) hydrazinecarbothioamide (TMBHC) as corrosion inhibitor on mild steel in 1 M hydrochloric acid was studied by Tafel polarization and electrochemical impedance spectroscopy (EIS) technique. The results showed that the inhibition efficiency (% IE ) of TMBHC increased with increasing inhibitor concentrations and also with increase in temperatures. TMBHC acted as a mixed type of inhibitor and its adsorption on mild steel surface was found to follow Langmuir’s adsorption isotherm. The evaluation of thermodynamic and activation parameters indicated that the adsorption of TMBHC takes place through chemisorption. The formation of protective film was further confirmed by scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

Three metal-organic frameworks (MOFs) were synthesised and their corrosion prevention behaviour was evaluated. Trimesic acid was used as a ligand to synthesis cobalt, nickel and copper-based MOFs in a mixture of solvents. MOFs were characterised by X-ray diffraction, FT-IR spectroscopy and thermogravimetric analysis. FE-SEM images of Ni-MOF and Cu-MOF showed one-dimensional nanorods, and foam-like morphology respectively. That of Co-MOF displayed large chunky particles with etched edges, and of non-uniform size and shape. The corrosion behaviour of MOF pigmented paint coated on mild steel was studied in 3.5% NaCl and 0.1 N HCl solutions using electrochemical impedance spectroscopy (EIS). In both solutions, Ni-MOF exhibited higher corrosion resistance than the Co-MOF and Cu-MOF. [ABSTRACT FROM AUTHOR]

The theoretical evaluations of the corrosion inhibition efficiency of 2-(3,4,5-tri-R-benzylidene) hydrazinecarbothioamide, (R = H, CH 3 , OCH 3 and NH 2 ), were done using RHF and DFT-B3LYP methods with 6-31G(d) basis set in gas phase, aqueous and acidic solutions. The correlation between the molecular structures of these compounds and their theoretically predicted inhibition effects was obtained from the quantum chemical evaluations, such that the structural parameters provided insights into the possible inhibition mechanism. 2-(3,4,5-triaminebenzylidene) hydrazinecarbothioamide showed a larger tendency of adsorption through chemisorption and physisorption and thus was identified to be the best potential candidate for excellent corrosion inhibition among the studied compounds. [ABSTRACT FROM AUTHOR]

In this research, we investigated the synthesis of a novel water-soluble bis azo pyrazolin-5-one (ABP) which was synthesized efficiently via the regioselective reaction of hydrazine with coumarin hydrazone (CMH). Also, we evaluate their anti-corrosion and anti-bacterial behavior. The inhibition efficiency of ABP in an acidic medium (1.0 M HCl) was evaluated using various electrochemical and surface morphology measurements. The novel bis pyrazole-based azo dye ABP (16 × 10−6 M) demonstrated a higher protection capacity (93.3 %). Tafel curves revealed that ABP was a mixed-type inhibitor. The adsorption of ABP on the C-steel (CS) surface is proven by the alteration in (R ct and C dl) impedance characteristics and obeyed the Langmuir isotherm model. SEM/EDX, AFM, and XPS surface examinations confirmed the enhancement of an adsorbed film protects the CS surface from acid corrosion at the appropriate dose. Furthermore, theoretical calculations using DFT and MC simulations were performed to identify the active sites on ABP molecules in charge of the adsorption and surface protection of the CS. The adsorption of bis pyrazole-based azo dye on the metal surface explained the protection mechanism. Moreover, the ABP screened for its antimicrobial activity against sulfate-reducing bacteria (SRB), and the calculated inhibition efficiency was 100 %. The current work presents significant results in manufacturing and producing novel water-soluble bis pyrazole-based azo dye derivative with high anti-corrosion and anti-microbial efficiency. [ABSTRACT FROM AUTHOR]

The inhibition ability of N,N ′ -bis(4-formylphenol)-1,2-Diaminocyclohexane (4-HCD) on the carbon steel in 1 M hydrochloric acid solution was studied by electrochemical techniques and weight loss measurements. 4-HCD inhibited steel corrosion in 1 M HCl solution significantly and the inhibition efficiency increased with 4-HCD concentration. The results indicated that after 5 h, this inhibitor has a maximum percentage inhibition efficiency of approximately 71% in the presence of 2 mM inhibitor. The adsorption of the inhibitor was followed Langmuir adsorption isotherm with the standard adsorption free energy of −25.66 kJ mol −1 . Computational investigations of the studied inhibitor are performed by using HF method with 6-31++G(d,p) and 6-311++G(d,p) basis sets. [ABSTRACT FROM AUTHOR]

The corrosion inhibition performances of three pyridazine derivatives, 6-methyl-4,5-dihydro-2H-pyridazine-3-one (MPYO), 6-phenyl-2H-pyridazine-3-one (PPYO) and 6-phenyl-2H-pyridazine-3-thione (PPYS) for mild steel in 1 M HCl solution were studied by gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Some thermodynamic parameters were calculated and discussed. The effect of molecular structure on the inhibition efficiency was theoretically studied by density functional theory (DFT). Experimental and theoretical studies agreed well and confirmed that PPYS is the best corrosion inhibitor among the studied organic compounds which was related to the presence of a more favorable adsorption center of S atom in its molecular structure. [ABSTRACT FROM AUTHOR]

Synergistic hydrogen bonded interaction of alkyl benzimidazoles and urea and its corrosion protection properties on mild steel in hydrochloric acid at different temperatures have been studied using polarization, electrochemical impedance spectroscopy (EIS), adsorption, surface studies and basic computational calculations. Quantum chemical approach was used to calculate some electronic properties of the molecules for the sake of correlating the synergistic interaction, inhibition properties and molecular structures. The corrosion inhibition efficiencies and the global chemical reactivity relate to parameters, such as total energy, energy of highest occupied molecular orbital ( E HOMO ), energy of lowest unoccupied molecular orbital ( E LUMO ) and gap energy (Δ E ). Urea interacts with benzimidazoles up to a bond length of approximately 1.8 Å. This represents the formation of a hydrogen bond between urea and benzimidazole molecules. Polarization and impedance studies also showed synergistic interaction between urea and benzimidazoles which offer extended inhibition efficiency toward mild steel in hydrochloric acid. [ABSTRACT FROM AUTHOR]

The corrosion inhibition effect of polypropylene glycol (PPG) without and with addition of iodide ions at mild steel/0.5 M H 2 SO 4 solution interface was investigated using chemical, electrochemical, and surface analysis methods at different temperatures. Results obtained showed that PPG inhibited the corrosion of mild steel in the acid environment. Addition of iodide ions to PPG is found to synergistically enhance the corrosion inhibitive ability of PPG with efficiency in the vicinity of 98.4%. Temperature–inhibition efficiency relationship suggest physisorption of PPG onto mild steel surface and chemisorption when PPG was combined with iodide ions. Potentiodynamic polarization results showed that PPG behaved as mixed type inhibitor but under anodic control when combined with iodide ions. The adsorption of PPG and PPG–iodide ions mixtures onto the metal surface followed Temkin adsorption isotherm model. [ABSTRACT FROM AUTHOR]

The three 2-aminobenzene-1,3-dicarbonitriles derivatives (ABDNs) namely 5′-amino-2,4-dihydroxy-4″-methyl-1,1′:3′,1″-terphenyl-4′,6-dicarbonitrile (ABDN-1), 5′-amino-2,2″,4-trihydroxy-1,1′:3′,1″-terphenyl-4′,6′-dicarbonitrile (ABDN-2) and 5′-amino-2,3″,4-trihydroxy-1,3-methoxy,1′:3′,1″-terphenyl-4′,6′-dicarbonitrile (ABDN-3) were synthesized and their corrosion inhibition properties on mild steel in 1 M HCl were investigated using weight loss and electrochemical techniques. Among the compounds investigated, ABDN-3 exhibited the best inhibition efficiency of 97.83% at 100 mg/L. Scanning electron microscopy (SEM) and dispersive X-ray spectroscopy (EDX) examinations was performed on inhibited and uninhibited mild steel samples to show the presence of ABDNs on mild steel surface. The potentiodynamic polarization studies reveal that all three studied inhibitors were of mixed type and their adsorption on the mild steel surface in 1 M HCl follows the Langmuir adsorption isotherm. Quantum chemical calculations studied were also performed to support weight loss and electrochemical experimental observations. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations using three methods, Hartree–Fock (HF), Møller–Plesset (MP) and density functional theory (DFT/B3LYP) method with SDD, 6−31G(d,p) and 6−31++G(d,p) basis sets are performed some benzaldehyde thiosemicarbazones and their thiole tautomers. The results of the quantum chemical calculations and experimental IE% which are belong to thione tautomers are subjected to correlation analysis and indicate that their inhibition effect are closely related to some quantum chemical parameters. The active sites are determined by using MEP diagrams, proton affinities and Fukui functions. The theoretically obtained results are found to be consistent with the experimental data which are reported for thione tautomers. [ABSTRACT FROM AUTHOR]

Three agro-waste products namely; watermelon rind extract (WMRE), watermelon seed extract (WMSE) and watermelon peel extract (WMPE) were investigated for their corrosion inhibition potentials for mild steel in HCl solution using electrochemical techniques at 25 °C. All the extracts inhibited acid-induced corrosion of mild steel in the order WMSE > WMRE > WMPE. Corrosion inhibition effect was found to be dependent on extracts’ concentrations. Inhibitive action of the extracts could be attributed to adsorption of the extracts’ components on mild steel surface by physisorption mechanism according to Langmuir adsorption isotherm model and functions as mixed-typed inhibitors as revealed by potentiodynamic polarization studies. [ABSTRACT FROM AUTHOR]

Acid corrosion may cause the deterioration of the fire resistance of the intumescent fire retardant coatings, especially for the coatings used in the acid polluted environment. This paper reported the results of an experimental study of degradation in fire protection performance of intumescent coating for steel elements after different times of immersion in the hydrochloric acid solution. After acid erosion, the thickness of the coating thinned, the surface became rough and had cracks and broken holes. The size of the pores in the char layer was larger and uneven, and some ‘cement’ parts were formed in the char layer. The TG/DTG results showed in the low temperature stage the curve was relatively flat. In the medium temperature stage, the number of the weight loss troughs decreased; the shape of the troughs simplified; and the top weight loss rate increased. In the high temperature stage, the troughs near 593 °C flattened gradually, and the top weight loss rate became smaller, while the top weight loss rate became larger around 674 °C. And there were significant changes in the thermal dynamic parameters. A prediction method of remained fire resistance property for the acid erosion coatings was proposed, by comprehensively considering the physical and chemical characteristics change trends of the corroded coating. And this method can be a reference for the fire safety evaluation of the built protected steel structure. [ABSTRACT FROM AUTHOR]

Acid corrosion may cause the deterioration of the fire resistance of the intumescent fire retardant coatings, especially for the coatings used in the acid polluted environment. This paper reported the results of an experimental study of degradation in fire protection performance of intumescent coating for steel elements after different times of immersion in the hydrochloric acid solution. After acid erosion, the thickness of the coating thinned, the surface became rough and had cracks and broken holes. The size of the pores in the char layer was larger and uneven, and some ‘cement’ parts were formed in the char layer. The TG/DTG results showed in the low temperature stage the curve was relatively flat. In the medium temperature stage, the number of the weight loss troughs decreased; the shape of the troughs simplified; and the top weight loss rate increased. In the high temperature stage, the troughs near 593 °C flattened gradually, and the top weight loss rate became smaller, while the top weight loss rate became larger around 674 °C. And there were significant changes in the thermal dynamic parameters. A prediction method of remained fire resistance property for the acid erosion coatings was proposed, by comprehensively considering the physical and chemical characteristics change trends of the corroded coating. And this method can be a reference for the fire safety evaluation of the built protected steel structure. [ABSTRACT FROM AUTHOR]

Corrosion protection properties of alkyl benzimidazoles (MBI, EBI & PBI) and ethylene thiourea (ETU) on mild steel in hydrochloric acid at different temperatures have been studied by polarization, electrochemical impedance study (EIS), adsorption, surface morphological studies and computational calculations. Synergistic and hydrogen bonded interaction takes place on metal surface and the extent of synergistic interaction increases with temperature. Computational quantum chemical approach is used to derive electronic properties of the inhibitor molecules for ascertaining the extent synergistic interaction, inhibitive effect and molecular structures. The corrosion inhibition efficiencies and the global chemical reactivity relate to parameters such as total energy, EHOMO, ELUMO and gap energy (ΔE). Ethylene thiourea interacts with alkyl benzimidazoles up to a bond length of approximately 1.99 Å. This interaction and bond length represents the formation of a hydrogen bond between the ETU and alkyl benzimidazoles. This synergistic interaction offer extended inhibition efficiency toward mild steel in hydrochloric acid especially at elevated temperatures. [ABSTRACT FROM AUTHOR]

Corrosion behavior of spheroidal graphite cast iron with different carbon contents has been studied. Immersion tests and electrochemical measurements were performed in sulfuric acid solutions of pH from 1.0 to 3.0. The corrosion current density of the cast iron is not a function of the content of carbon and the area of graphite particles at the surface. The corrosion current density of the cast iron is higher than the reported values of pure iron. This results from the promotion of both the anodic and cathodic reactions. The dependences of the corrosion potential and the corrosion current density on pH are the same as those of pure iron. [ABSTRACT FROM AUTHOR]

Abstract: Weight loss and electrochemical (open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy) techniques were used to assess the effectiveness of ethanol and acetone extracts of coconut coir dust as corrosion inhibitor for mild steel in 0.5 M H2SO4 solution at 30–60 °C. It was found that both ethanol and acetone extracts of coconut coir dust retard the dissolution of mild steel in 0.5 M H2SO4 solution, but a pronounced effect was noted with ethanol extract. The inhibition efficiency increased with increase in extract concentration but decreased with rise in temperature, which is suggestive of physical adsorption mechanism. Addition of KI was found to synergistically enhance the protective ability of coconut coir dust extracts obtained from both solvent systems investigated. The synergistic effect was confirmed from the synergism parameter (S 0) which was found to be greater than unity. Potentiodynamic polarization result suggests that coconut coir extracts functioned as mixed-type inhibitor. The adsorption of coconut coir dust extracts onto the mild steel surface followed Freundlich adsorption isotherm model. The mechanism of physisorption of the extracts onto the steel surface is proposed from the trend of inhibition efficiency with temperature which is corroborated by the values of activation parameters obtained from the experimental data. [ABSTRACT FROM AUTHOR]

Highlights: [•] (S)-4,5,6,7-Tetrahydrobenzo[d]thiazole-2,6-diamine (TDA) was investigated as a corrosion inhibitor for mild steel. [•] Surface studies reveal the adsorption of TDA on the mild steel surface. [•] TDA adsorption on mild steel is a spontaneous process and classical Langmuir adsorption is followed. [•] DFT calculations showed the optimized TDA molecular structures and other quantum chemical parameters. [Copyright &y& Elsevier]

Austenitic stainless steels are the main materials of construction in nuclear spent fuel reprocessing and waste management plants that use nitric acid (HNO3) as the process fluid. In this study, it has been shown that the potential, attained either by addition of oxidizing ions or by external application, determines the corrosion behavior of stainless steels. An equation derived from curve fitting of the measured corrosion data is proposed for predicting the corrosion rates of a specific stainless steel at any given operating potential. The influence of microstructure ("step," "dual," and "ditch") of Type 304L (UNS S30403) stainless steel was also studied. [ABSTRACT FROM AUTHOR]

Abstract: The inhibitive action of ethanol extracts from leaves (LV), bark (BK) and roots (RT) of Nauclea latifolia on mild steel corrosion in H2SO4 solutions at 30–60°C was studied using weight loss and gasometric techniques. The extracts were found to inhibit the corrosion of mild steel in H2SO4 solutions and the inhibition efficiencies of the extracts follow the trend: RT>LV>BK. The inhibition efficiency increased with the extracts concentration but decreased with temperature rise. Physical adsorption of the phytochemical components of the plant on the metal surface is proposed as the mechanism of inhibition. The adsorption characteristics of the inhibitor were approximated by the thermodynamic-kinetic model of El-Awady et al. [Copyright &y& Elsevier]

To investigate the corrosion of centrifugal contactors in the spent nuclear fuel treatment process called UREX+, corrosion of UNS S30403 stainless steel has been studied in three acidic aqueous solutions of 5.0 M nitric acid (HNO3), 5.0 M HNO3 + 0.1 M hydrofluroric acid (HF). and 5.0 M HN03 +0.1 M HF + 0.1 M Zr4+. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were conducted at temperatures of 25, 40. and 80°C and different hydrodynamic conditions (0, 1.000. 2,000 rpm). The results showed that the mixture of HNO3 and HF was the most corrosive environment. Addition of Zr4+ ions to this acidic solution reduced the corrosion caused by HF to levels similar to those found in HN03 solutions. Higher corrosion rates were obtained as the solution's temperature increased while hydrodynamic conditions had a less significant effect on corrosion rates. [ABSTRACT FROM AUTHOR]

Corrosion of lead silicate glass (LSG] contacting 0.5 M aqueous nitric acid (HNOJ was investigated via scanning electron microscopy, energy-dispersive spectroscopy, inductively coupled plasma analysis, and weight-loss measurement to determine the respective contributions of the ion-exchange vs. the hydrolysis reactions. The LSG having XM = Pb + K + Na/Si mole ratios of less than 0.7 showed very little weight loss with no Si network deterioration. At XM > 0.7, the mechanism changed into the hydrolysis, which caused the formation of a networkless gel layer resting at the solid/liquid interface. Addition of titania (TiO2) and zirconia (ZrO2) had disparate effects: XM < 0.7 improved corrosion resistance: while XM> 0.7 caused detrimental consequences. [ABSTRACT FROM AUTHOR]

The corrosion inhibition of lead in 0.1 M hydrochloric acid (HCI) was investigated in the absence and presence of different concentrations of N-phenylcinnamimide (C15H13NO) and some of its p-derivatives. Weight loss. Tafel polarization, and anodic polarization under constant current (three independent techniques) were used. The weight-loss results showed that the corrosion rate of the lead decreases by increasing the immersion period and the inhibitor concentration. Tafel polarization studies showed that theses inhibitors retard both the anodic and the cathodic reactions through blocking the active corrosion sites on the metal surface. The data of the anodic polarization under constant current showed that as the concentration of the inhibitor increases, the dissolution potential of the lead electrode, the duration time of the dissolution arrest, and the reactivation potential of the arrest were affected. The adsorption of the studied inhibitors on the lead surface obeys the Langmuir adsorption isotherm equation. The inhibition action of the inhibitors was detected from the three techniques and was found to decrease in the order: N-(p-methoxyphenyl)cinnamimide > N-(p-methylphenyl)cinnamimide > N-phenylcinnamimide > N-(p-nitrophenyl)cinnamimide. The inhibition action o fall the inhibitors was found to depend on the nature of the attached group in the p-position of the benzene ring. [ABSTRACT FROM AUTHOR]

Artificial neural network models were used for estimation of corrosion behaviour of a cold isostatically pressed (CIP) high-purity alumina ceramics in aqueous HCl solution. Corrosion tests were performed with initial mass concentrations of HCl aqueous solution of 2, 10 and 20 wt. % at room temperature. Immersion times were 24, 48, 72, 120, 168 and 240 hours. Chemical stability was monitored by the amount of Al3+, Mg2+, Ca2+, Na+, Si4+ and Fe3+ ions eluted in different concentrations of HCl solution by means of atomic apsorption spectrometry (AAS), expressed as the amount of eluted ions in mg per square centimetre of test alumina area (μg Mn+/cm²). The initial HCl aqueous solution concentration and immersion time were inputs to the neural network, and the output was the amount of eluted ions (μg Mn+/cm²). Error back-propagation learning algorithm, with Levenberg -Marquardt method, was applied to the feed forward neural networks. [ABSTRACT FROM AUTHOR]

The environmental and economic benefits have been the driving force in search of efficient corrosion inhibitors for iron/steel used in industrial acidic medium. This study reports on berberine isolated from methanol extract of high-altitude (1347 m) shrub Mahonia nepalensis as a highly efficient and thermally stable corrosion inhibitor for mild steel (MS) in 1.0 M H 2 SO 4 simulating acid pickling condition. The weight-loss and electrochemical methods revealed the fast adsorption of berberine. Significant Findings: It achieved above 91% inhibition efficiency (IE) in 0.25 h and reached 94% in 6 h for 1000 ppm berberine. The IE increased with concentration and temperature, giving an IE of 97.2% at 328 K, which makes it a promising candidate for industrial application. It behaved as a mixed type of inhibitor as revealed by open circuit potential and polarization curves. The results indicated suppression of the corrosion by effectively forming an adsorbed berberine layer on the MS surface. Adsorption of the berberine followed a Langmuir adsorption isotherm. The thermodynamic parameters such as activation energy (43.19 kJ/mol), free energy (−35.05 kJ/mol), enthalpy (40.55 kJ/mol), and entropy (−97.83 J/molK) of adsorption supported both physical and chemical interactions of berberine with MS surface. The obtained results also revealed that the adsorption process was endothermic and spontaneous in nature. [ABSTRACT FROM AUTHOR]

Pomelo peel extract (PPE) was evaluated as green and renewable corrosion inhibitor for mild steel in 1.0 mol/L H 3 PO 4 solution. The inhibition behaviour was studied using mass loss, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements. The chemical structure of PPE was investigated using Fourier transform infrared (FT-IR) and ultraviolet-visible (UV–vis) spectroscopy. The corrosion morphology of mild steel was analysed via scanning electron microscopy (SEM). The adsorption thermodynamics and kinetics was discussed. The results show that PPE confers an acceptable long-term effect (inhibition efficiency of 95.0% and 92.8% for corroding 23 h and 224 h in the presence of 5.0 g/L PPE inhibitor) and functions as a mixed inhibitor. The adsorption of PPE on mild steel simultaneously follows the Langmuir, El-Awady and Temkin isotherms at 35, 45 and 55 °C. PPE is mixed adsorption dominated with physical adsorption at room temperature or with higher PPE concentrations. PPE possesses many polar functional groups such as hydroxyl, carbonyl and hetero-aromatic rings. The inhibition mechanism is closely related to these polar groups, as is the surface coverage of steel. [ABSTRACT FROM AUTHOR]

Abstract: The inhibition of the corrosion of mild steel in hydrochloric acid solutions by 4-amino-5-phenyl-4H-1,2,4-trizole-3-thiol (APTT) inhibitor was studied using weight loss technique. Basic kinetic parameters of the corrosion inhibition process were obtained by reaction kinetic equations. Rustles show that the inhibition increases with increasing of inhibitor concentration. Kinetic calculations show that the maximum value of time for which the corrosion rate increases twice the initial one, while time for which the mass of the sample subjected to corrosion decreases twice the initial one were at 8×10−4 M of APTT. The dynamics were described by an exponential kinetic equation of self-accelerating reactions in the absence of inhibitor and by an equation of a zero order in its presence. [Copyright &y& Elsevier]

• The inhibition effect of acetohydroxamic acid (AHA) and benzohydroxamic acid (BHA) on corrosive dissolution of copper in 1 M HCl medium was studied. • AHA and BHA acted as mixed type inhibitors. • BHA and AHA exhibited the maximum efficiencies of 98.49% and AHA 95.90% respectively. • Adsorption of the BHA and AHA obeyed the Langmuir adsorption isotherm model. • Both BHA and AHA strongly and spontaneously adsorbed on the metal (copper) surface/electrolyte interfaces. The inhibition effect of acetohydroxamic acid (AHA) and benzohydroxamic acid (BHA) on corrosive dissolution of copper in 1 M HCl medium was studied using gravimetric, electrochemical (PDP and EIS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and density functional theory (DFT) methods. Inhibition efficiencies of AHA and BHA are increases on increasing their concentrations and decreases as temperature increased. Results showed that AHA and BHA acted as mixed type inhibitors. The BHA and AHA exhibited the maximum efficiencies of 98.49%and AHA 95.90% respectively. Adsorption of the BHA and AHA obeyed the Langmuir adsorption isotherm model. Gibbs free energy of adsorption (Δ G ads), adsorption constant (K ads) and activation energy (E a) values showed that both BHA and AHA strongly and spontaneously adsorbed on the metal (copper) surface/electrolyte interfaces. The gravimetric and electrochemical studies were supported by EDS coupled SEM analyses. Inhibitive properties of BHA and AHA obtained from experimental methods was supported by DFT. Numerous parameters were computed and discussed in order to described their adsorption behaviour. [ABSTRACT FROM AUTHOR]

Lannea coromandelica leaf extract (LCLE) as a corrosion inhibitor in 1 M H 2 SO 4 was investigated by weight loss and electrochemical techniques. Inhibition efficiency of LCLE was found to increase with increasing concentration but decreased with increasing temperature. Polarization measurements revealed that the LCLE acted as a mixed type inhibitor. Nyquist plots showed that on increasing the LCLE concentration, the charge transfer resistance increased and the double layer capacitance decreased. The adsorption of LCLE on mild steel obeyed the Langmuir adsorption isotherm. FT-IR, XRD, SEM and AFM techniques confirmed the adsorption of LCLE on mild steel surface. [ABSTRACT FROM AUTHOR]