Electrochemical and thermodynamic investigation of diniconazole and triadimefon as corrosion inhibitors for copper in synthetic seawater

This paper presents the investigation of diniconzole and triadimefon as chemical corrosion inhibitors for freshly polished copper in synthetic seawater (3.5% NaCl solution). Determination of weight loss, polarization curves, electrochemical impedance spectroscopy (EIS), and SEM, were performed to analyze the inhibiting performance of these compounds. Polarization curves show that they act as mixed-type inhibitors. EIS indicates that an adsorption film of the inhibitors is formed on copper surface. The highest values of inhibition efficiency are respectively, 99.2% and 97.3% at 100 mg/L concentration. Thermodynamic calculation suggests that chemisorptions between the compounds and copper are accordance with Langmuir adsorption isotherm.     

Potent inhibition of copper corrosion in neutral chloride media by novel non-toxic thiadiazole derivatives

Inhibiting effect of two novel non-toxic thiadiazole derivatives on copper were investigated in 3.5% NaCl solution using weight loss and electrochemical measurements. Presence of inhibitors and increase of concentration greatly decrease corrosion rate, parameters determined from polarization curves and EIS plots show that inhibitors decrease both cathodic and anodic current densities, suppressing charge transfer process by adsorption on copper surface. Thermodynamic calculation indicates chemisorption obeys Langmuir isotherm. Surface layers were characterized by SEM coupled with EDX. Raman micro-spectroscopy reveals that inhibitor molecules suppress copper corrosion via formation of thiadiazole–Cu complex. Relationships between inhibition efficiency and molecular orbital were also evaluated.     

The influence of pH value on the efficiency of imidazole based corrosion inhibitors of copper

The aim of this work is to establish the correlation between the solution pH and the inhibiting efficiency of two imidazole compounds (4-methyl-1-phenyl imidazole and 4-methyl-1-(p-tolyl) imidazole) in protection of copper from corrosion in chloride media.It was found that the inhibiting efficiency of both studied imidazoles enhances with the increase of the solution pH value, from about 20% in 0.5 M HCl to 92% in 0.5 M NaCl. This improvement was ascribed to stronger adsorption of neutral imidazole molecule, which can be expected at higher pH values, than that of the protonated imidazole cation, which may be expected in acid solutions.     

Dry and wet lab studies for some benzotriazole derivatives as possible corrosion inhibitors for copper in 1.0 M HNO3

With contrast to the traditional techniques of identifying and synthesizing new corrosion inhibitors in wet lab, a prior dry-lab process, followed by a wet-lab process is suggested by using cheminformatics tools. Quantum chemical method is used to explore the relationship between the inhibitor molecular properties and its inhibition efficiency. The density function theory (DFT) is also used to study the structural properties of three selected benzotriazole derivatives namely, benzotriazole-1-carboxamide (BCA), 1H-benzotriazole-1-acetonitrile (BAN) and benzotriazole-1-carbonyl chloride (BCC) in aqueous phase. It is found that when the benzotriazole derivatives adsorb on the copper surface, molecular structure influences their interaction mechanism. The inhibition efficiencies of these compounds showed a certain relationship to highest occupied molecular orbital (HOMO) energy, Mulliken atomic charges and Fukui indices. A wet lab study has been carried out using weight loss, Tafel polarization and impedance measurements to evaluate their inhibition performance in 1.0 M HNO₃ solutions at 25 °C. Adsorption takes place by a direct chemisorption on the exposed copper surface, while it most probably occurs via hydrogen bonding on the oxidized surface. BCA was the most effective among the tested inhibitors, while BCC was less effective than BAN. Results obtained from dry-lab process are in good agreement with those recorded from wet-lab experiments.     

2-Mercaptobenzimidazole as a copper corrosion inhibitor: Part I. Long-term immersion, 3D-profilometry,and electrochemistry

The high corrosion inhibition effectiveness of 2-mercaptobenzimidazole (MBIH) in 3 wt.% aqueous NaCl solution is reported using long term immersion tests, 3D-profilometry, electrochemical impedance spectroscopy, and potentiodynamic curve measurements. The high corrosion inhibition performance was proven after 180 days of immersion. The impedance spectra were characterized by two time constants relating to charge transfer and finite layer thickness or semi-infinite diffusion of copper ions through the surface layer, therefore Cu corrosion in solution containing MBIH follows kinetic-controlled and diffusion-controlled processes. Moreover, it is shown that MBIH is a mixed-type inhibitor.     

Electrochemical quartz crystal microbalance and electrochemical impedance spectroscopy study of copper corrosion inhibition by imidazoles

The aim of this work is to obtain deeper insight into the mechanism of the protective action of three imidazole-based corrosion inhibitors. Investigations were performed on copper in 3% NaCl, by electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance measurements. The kinetic changes in the corrosion processes were monitored over time. In spite of similar molecular structure, differences in the inhibiting mechanism of three imidazole compounds were observed. The two inhibitors with a tolyl substituent decreased the copper corrosion rate due to the formation of a thin adsorbate layer; however, slow formation of a thick layer was observed for 4-methyl-1-phenyl imidazole. From electrochemical impedance spectroscopy studies, it was observed that all three inhibitors protected the copper efficiently, and in some cases, the degree of the protection increased with time.     

Adsorption and corrosion inhibition of phytic acid calcium on the copper surface in 3 wt% NaCl solution

The adsorption and corrosion protection effect of phytic acid calcium (PAC) film on the copper surface in 3 wt% NaCl solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Raman spectroscopy. Polarization curves indicate that PAC is a mixed inhibitor, affecting both cathodic and anodic corrosion currents. The inhibition efficiency of PAC film reached 92.53% at an optimized condition. Adsorption of PAC molecules on the surface followed Langmuir adsorption isotherm and the standard Gibbs energy of −37.32 kJ mol⁻¹ indicated a chemisorptive way. Raman studies suggested that PAC molecule chemically anchored at the surface via PO groups.     

Novel application of a hormone biosynthetic inhibitor for the corrosion resistance enhancement of copper in synthetic seawater

Effects of a hormone biosynthetic inhibitor on corrosion resistance of copper in synthetic seawater under various conditions were evaluated via quantum chemistry calculations, weight loss, electrochemical techniques, SEM, EDS, and FTIR. Comparable results show that uniconazole acts as a mixed-type inhibitor, suppressing charge transfer process by adsorption on copper surface. Thermodynamic calculation indicates that chemisorption is in accordance with Langmuir isotherm and adsorption amount increases with immersion time. The corrosion resistance with inhibitor under alkaline conditions is better than that under acidic or neutral conditions. Good inhibition performances at different temperatures and during a long time immersion are observed.     

The corrosion inhibition of copper in hydrochloric acid solutions by a tripeptide compound

The efficiency of glutathione as a non-toxic corrosion inhibitor for copper in 0.5 M HCl has been studied by using the weight-loss technique, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Maximum protection efficiency reaches about 92.7% for glutathione at 10 mM concentration level. Results obtained from potentiodynamic polarization and impedance measurements are in good agreement. The adsorption of glutathione on copper surface follows Langmuir isotherm. The adsorption free energy of glutathione on copper (−32 kJ mol⁻¹) reveals a strong physical adsorption of the inhibition on the metal surface.     

A new corrosion inhibitor for copper protection

Methyl 3-((2-mercaptophenyl)imino)butanoate (MMPB) was synthesized as inhibitor compound for copper protection. The molecule was designed with azole, thiol functional groups and carboxylate tail group. The inhibition efficiency was examined in acidic chloride media, by means of various electrochemical and spectroscopy techniques. Electrochemical study results showed that high efficiency of MMPB was mainly related with its capability of complex formation with Cu(I) at the surface. The thiol group also improves the adsorptive interaction with the surface, as the carboxylate groups provide extra intermolecular attraction.     

2-Amino-5-(4-pyridinyl)-1,3,4-thiadiazole monolayers on copper surface: Observation of the relationship between its corrosion inhibition and adsorption structure

Corrosion inhibition behavior of 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole (4-APTD) monolayers on copper surface were investigated by electrochemical impedance spectroscopy (EIS), electrochemical polarization measurement and surface-enhanced Raman scattering (SERS) experiment. The EIS mechanism of the copper surface with 4-APTD monolayers fitted to the mode of R(Q(R(QR))). The electrochemical polarization measurements indicated high inhibition efficiency of about 90.4%. SERS results suggested that 4-APTD molecules anchored at copper surface in a tilted orientation directly via N³ and N¹² atoms. The transition adsorption states of 4-APTD on the copper surface were observed as the potential applied from 0 to −1.6 V vs. SCE.     

Benzimidazole and its derivatives as corrosion inhibitors for mild steel in 1M HCl solution

In this paper, the inhibition ability of benzimidazole and its derivatives against the corrosion of mild steel in 1M HCl solution was studied. The change of impedance parameters observed by variation of inhibitors concentration within the range of 50-250 ppm was an indication of their adsorption. The thermodynamic adsorption parameters proposed that these inhibitors retard both cathodic and anodic processes through physical adsorption and blocking the active corrosion sites. The adsorption of these compounds obeyed the Langmuir’s adsorption isotherm. The inhibition efficiency was increased with inhibitor concentration in the order of 2-mercaptobenzimidazole > 2-methylbenzimidazole > benzimidazole, which is in accordance with the variation of apparent activation energy of corrosion.     

Two pyrazine derivatives as inhibitors of the cold rolled steel corrosion in hydrochloric acid solution

The inhibition effect of two pyrazine derivatives of 2-aminopyrazine (AP) and 2-amino-5-bromopyrazine (ABP) on the corrosion of cold rolled steel (CRS) in 1.0 M hydrochloric acid (HCl) was studied by weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy (EIS) methods. The results show that both AP and ABP are good inhibitors, and inhibition efficiency follows the order: ABP > AP. The adsorption of each inhibitor on CRS surface obeys Langmuir adsorption isotherm. Potentiodynamic polarization curves show that two pyrazine derivatives act as mixed-type inhibitors. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability.     

Phosphate ions used as green inhibitor against copper corrosion in tap water

Three dosages of ions are evaluated as corrosion inhibitors of copper in artificial tap water by measuring the corrosion potential, polarization resistance, electrochemical impedance and reflectance spectra. The water is moderately hard, highly carbonated and chloride-rich. The results show that the surface film is composed by Cu₂O. When the inhibiting agent is added, the film becomes thicker, denser and more compact. This behaviour is attributed to CuO incorporating into the passive layer. The optimal dosage of inhibitor is 10 mg l⁻¹ P when the polarization resistance increases three times. The inhibitor retards the pit initiation, without hindering pit growth.     

Copper corrosion in sodium dodecyl sulphate solutions and carbon nanotube nanofluids: A modified Koutecky–Levich equation to model the agitation effect

Copper corrosion in sodium dodecyl sulphate (SDS) solutions and carbon nanotube (CNT) nanofluids were studied by potentiodynamic polarization. For the corrosion current densities calculations, Koutecky–Levich equation was modified to model the combined charge and mass transport. 0.005 M SDS reduced the copper corrosion current density by 81%. Higher SDS concentrations enhanced corrosion. Stirring SDS solutions increased the corrosion current density by ∼75%. By adding CNT to SDS solution, the corrosion current density first decreased and then remained constant. Stirring CNT nanofluids didn’t change the corrosion current density. An adsorbed CNT layer on copper controlled the corrosion process in CNT nanofluids.     

Investigation of the inhibition effect of indole-3-carboxylic acid on the copper corrosion in 0.5 M H2SO4

Inhibition of the copper corrosion by means of indole-3-carboxylic acid (ICA), was studied in 0.5 M H₂SO₄ 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.     

Chlorhexidine digluconate as corrosion inhibitor for carbon steel dissolution in emulsified diesel fuel

Nitrogen oxide (NO_x) and particulate matter (PM) emissions from diesel engines are reduced by mixing water in the diesel fuel in the form of water-in-diesel emulsion. The results of experiment showed that blend of span 80 and tween 80 at HLB 6 was found to be the most suitable emulsifier for water/diesel emulsion. The effect of chlorhexidine digluconate on the corrosion of carbon steel electrode in aerated stagnant water/diesel emulsion solution has been studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiency was found to increase with increasing inhibitor concentration. The inhibition is attributed to adsorption of the inhibitor on the carbon steel surface. The adsorption behavior of chlorhexidine digluconate on the carbon steel surface follows Temkin-type isotherm. The standard free energies of adsorption are lower than 40 kJ mol⁻¹ confirming the physical adsorption of chlorhexidine digluconate on the electrode surface. Chlorhexidine digluconate has a significant inhibiting effect on the growth of micro-organisms in the liquid fuel and protection efficiencies up to 99.9% were measured.     

Electrochemical and quantum chemical studies of some indole derivatives as corrosion inhibitors for C38 steel in molar hydrochloric acid

A comparative study of 9H-pyrido[3,4-b]indole (norharmane) and 1-methyl-9H-pyrido[3,4-b]indole (harmane) as inhibitors for C38 steel corrosion in 1 M HCl solution at 25 °C was carried out. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were applied to study the metal corrosion behavior in the absence and presence of different concentrations of these inhibitors. The OCP as a function of time were also established. Cathodic and anodic polarization curves show that norharmane and harmane are a mixed-type inhibitors. Adsorption of indole derivatives on the C38 steel surface, in 1 M HCl solution, follows the Langmuir adsorption isotherm model. The values were calculated and discussed. The potential of zero charge (PZC) of the C38 steel in inhibited solution was studied by the EIS method, and a mechanism for the adsorption process was proposed. Raman spectroscopy confirmed that indole molecules strongly adsorbed onto the steel surface. The electronic properties of indole derivates, obtained using the AM1 semi-empirical quantum chemical approach, were correlated with their experimental efficiencies using the linear resistance model (LR).     

Corrosion inhibition of copper in neutral chloride media by a novel derivative of 1,2,4-triazole

The efficiency of a new corrosion inhibitor, the bis-(4-amino-5-mercapto-1,2,4-triazol-3-yl)-butane (BAMTB), on copper was investigated in an aerated 3% NaCl solution using various techniques. Voltammetry, chronopotentiometry and electrochemical impedance spectroscopy (EIS) were performed to evaluate the inhibition efficiency of BAMTB. The surface layers were also characterized by Raman micro-spectroscopy and by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Potentiodynamic polarization curves showed that BAMTB is a mixed-type inhibitor for copper in neutral chloride solution and is even more efficient than the reference compound benzotriazole.     

Three pyrazine derivatives as corrosion inhibitors for steel in 1.0 M H2SO4 solution

The inhibition effect of three pyrazine derivatives of 2-methylpyrazine (MP), 2-aminopyrazine (AP) and 2-amino-5-bromopyrazine (ABP) on the corrosion of cold rolled steel (CRS) in 1.0 M H₂SO₄ solution was studied by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results show that all pyrazine compounds are good inhibitors, and inhibition efficiency follows the order: ABP > AP > MP. The adsorption of each inhibitor on CRS surface obeys Langmuir adsorption isotherm. For all these pyrazine derivatives, they act as mixed-type inhibitors. The probable inhibitive mechanism is proposed from the viewpoint of adsorption theory.