Using Indole to Inhibit Copper Corrosion in Aerated 0.5 M Sulfuric Acid (original) (raw)
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Corrosion Inhibition of Copper in Aerated 0.5 M Sulfuric Acid by Indole-2-Carboxylic Acid
CORROSION, 2005
The inhibiting action of indole-2-carboxylic acid (C 9 H 7 NO 2) on the corrosion of commercial copper in aerated 0.5 M sulfuric acid (H 2 SO 4) has been investigated in the temperature range from 25°C to 55°C by weight loss, potentiodynamic and analytical tests, and the determination of double-layer capacitance. The results have revealed a good inhibitor effi ciency, up to 98% in the concentration range from 1 × 10-4 M to 4 × 10-3 M. Indole-2-carboxylic acid has been found to act as a mixed inhibitor. The kinetics of Cu + and Cu 2+ formation that followed in 72 h of gravimetric testing shows that indole-2carboxylic acid probably affects the corrosion reaction mechanism through complexes with cuprous ions. The corrosion rates determined through weight-loss measurements are much higher than those obtained with potentiodynamic tests. This is in accord with other researchers who have found limitations to the extrapolation of polarization curves (and to the theory of mixed potentials) in the determination of corrosion rates. The adsorptive behavior of indole-2-carboxylic acid also has been investigated in a wide potential range (-900 mV to 200 mV with regard to corrosion potential [E corr ]).
Corrosion Science, 2008
Inhibition of the copper corrosion by means of indole-3-carboxylic acid (ICA), was studied in 0.5 M H 2 SO 4 solutions in the temperature range from 25°C to 55°C using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results obtained from the both measurement techniques revealed good inhibitor efficiency in the studied concentration range. Nyquist plots showed depressed semicircles with their centre below real axis. Moreover, the impedance spectra in the case of both non inhibited solutions and inhibited ones by means of lower inhibitor concentrations exhibited Warburg impedance. The adsorption behaviour of ICA followed Langmuir's isotherm.
Applied Surface Science, 2006
Inhibition of mild steel corrosion in deaerated 0.5 M sulfuric acid solutions containing various concentrations of indole-5-carboxylic acid is studied in the temperature range from 25 to 55 8C using weight-loss, potentiodynamic and spectrophotometric tests. The adsorptive behaviour of inhibitor is also investigated using electrochemical impedance spectroscopy measurements. The indole-5-carboxylic acid is found to shift the corrosion potentials towards more noble values. This shift indicates that the addition of inhibitor mainly affects the anodic process, raising the anodic overpotential more than that of the cathodic, i.e. the indole-5-carboxylic acid behaves as mixed-type inhibitor. Because the cathodic Tafel slopes for hydrogen reduction (b c) are affected, the inhibitor probably affects the hydrogen reduction mechanism. The activation energy values (E a) indicate that the indole-5-carboxylic acid increases the activation energy of the corrosion reaction. The adsorption behaviour of indole-5carboxylic acid follows Langmuir's isotherm. Both the low values of ÀDG ads and its decrease with temperature suggest physical adsorption. Double layer capacitance-potential curves indicate considerable adsorption of the inhibitor in the potential range (À400 to À800 mV/ SCE).
Journal of the Taiwan Institute of Chemical Engineers, 2019
Levamisole (LMS) and 4-phenylimidazole (PIZ), used as corrosion inhibitors of copper in sulfuric acid solution were explored by electrochemical tests, morphology analysis and theoretical calculation. At the concentration of 8 mM, the maximum corrosion inhibition efficiencies of LMS and PIZ are 99.03% and 95.84%, respectively. All test data found that LMS had better corrosion inhibition performance than PIZ. LMS is a cathodic corrosion inhibitor, while PIZ belongs to a mixed-type corrosion inhibitor. Electrochemical results indicate that the corrosion inhibition efficiency has the same trend when the concentration of corrosion inhibitor increases. Scanning electron microscope and atomic force microscope were applied to research the surface morphology of copper samples under different conditions. X-ray photoelectron spectroscopy and Langmuir adsorption isotherm model were utilized to explain adsorption means. What is more, Langmuir adsorption isotherm model indicates the coexistence of physisorption and chemisorption for the two inhibitors. Besides, the adsorption between LMS and copper is more prone to chemical adsorption. The mechanism of metallic copper and corrosion inhibitors was explored through quantum chemistry studies and molecular dynamics simulation.
Inhibiting effects of 2-mercapto-1-methylimidazole on copper corrosion in 0.5 M sulfuric acid
Journal of Saudi Chemical Society, 2010
The inhibiting efficiency of 2-mercapto-1-methylimidazole (MMI) on copper corrosion in sulfuric acid was investigated at 30°C. Its effectiveness was assessed through electrochemical impedance spectroscopy, potentiodynamic polarization and gravimetric measurements. The results of study reveal that the inhibition efficiency of MMI depends on its concentration and attains approximately 81% at 10 À4 M. The inhibitor was adsorbed on the copper surface according the Langmuir adsorption isotherm model. The value of standard free energy of adsorption was calculated from this isotherm.
Corrosion behavior of copper in 1.0 M Sulfuric acid containing either Imidazole (IM), 2-Methylimidazole (MIM) or Benzimidazole (BIM) was investigated experimentally via weight loss measurements and UV-Spectroscopy. The density functional theory (DFT) at the B3LYP/6-31G+ (2d, p) basis set level in gas phase is also applied here for theoretical study. Some quantum chemical parameters and the Mulliken charge densities on the optimized structures for imidazole compounds were determined. All theoretical results and experimental inhibition efficiencies of inhibitors were subjected to correlation analyses. Results obtained reveal that BIM is the best inhibitor and the inhibition efficiency (EW%) follows the sequence: BIM >MIM > IM. The adsorption behavior of BIM followed Langmuir's isotherm. Cu(I)−BIM complex formation was confirmed by UV spectroscopy.
Corrosion Inhibition of Nickel in HCl Solution by Some Indole Derivatives
2013
Some indole derivatives are investigated as corrosion inhibitors for nickel in 0.5 M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. A significant decrease in the corrosion rate of nickel was observed in the presence of investigated indole derivatives. Potentiodynamic polarization curves revealed that these inhibitors acted as mixed-type inhibitors, affecting both cathodic and anodic corrosion processes. The adsorption of the inhibitors on nickel surface in 0.5 M HCl was found to follow Frumkin adsorption isotherm. Thermodynamic adsorption parameters (K ads , ΔG°a ds) of investigated inhibitors were calculated from the linear form of Frumkin adsorption isotherm. Activation parameters of the corrosion process were calculated and discussed. EIS was used to investigate the mechanism of corrosion inhibition. Correlation between the inhibition efficiency and the structure of these inhibitors are presented.
Inhibitive Action of Imidazoles for Copper Corrosion in Sulfuric Acid Medium
JOURNAL OF ADVANCES IN CHEMISTRY
The corrosion inhibition of copper in the presence of 10-3 M of imidazole derivatives; Imidazole (IM), 2-Methyle imidazole (MIM), Benzimidazole (BIM) has been investigated in 1.0 M H2SO4 solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Relationship between molecular structure and their inhibition efficiency was elucidated by quantum chemical calculations using the density functional theory (DFT) at the B3LYP/6-31+G(d,p) level. Inhibition efficiency of these compounds which has been evaluated via experimental methods was accorded with reported theoretical ones, and following the same order as BIM ˃ MIM ˃ IM.
Rem: Revista Escola de Minas, 2013
The adsorption of organic substances in metals and in different media has been attributed to different effects, such as the carbon chain size, type or number of heteroatom in the molecule structure, reactivity, the steric effect, among others. The objective of this work is to study the electrochemical indole behavior for AISI 430 stainless steel (SS), when changing the study media from H 2 SO 4 1 mol L-1 to HCl 1 mol L-1. The experimental techniques used are as follows: the open-circuit potential, anodic and cathodic potentiodinamic polarization, electrochemical impedance spectroscopy, optical microscopy and scanning electron microscopy. These results suggest that the adsorption of indole in the presence of SO 4-2 is lower than in the medium containing Cl-, which is justified by the indole action as a weak acid, because it has only a single pair of electrons, which is displaced and takes part in the π-electron aromatic system; thus the first step of the indole reaction in acid media is the protonation and generation of an indole cation.