Stearate as a green corrosion inhibitor of magnesium alloy ZE41 in sulfate medium

The efficiency of stearate as a corrosion inhibitor for magnesium alloy ZE41 has been studied in sodium sulfate medium, employing electrochemical techniques like potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of polarization study imply that stearate functions as a mixed-type corrosion inhibitor with a predominant anodic control. The adsorption of stearate on alloy surface is found to obey the Langmuir adsorption isotherm. The proposed inhibition mechanism involved adsorption of stearate onto metal surface, followed by precipitation of magnesium stearate within the microdefects of Mg(OH)₂ surface film which enhanced the barrier effect of an otherwise porous partially protective film.     

Surface morphological and impedance spectroscopic studies on the interaction of polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) with mild steel in acid solutions

The inhibition of mild steel corrosion in aerated acid mixture of 0.5 N H₂SO₄ and 0.5 N HCl solution was investigated using potentiodynamic polarization studies, linear polarization studies, electrochemical impedance spectroscopy, adsorption, and surface morphological studies. The effect of inhibitor concentration on corrosion rate, degree of surface coverage, adsorption kinetics, and surface morphology is investigated. The inhibition efficiency increased markedly with increase in additive concentration. The presence of PEG and PVP decreases the double-layer capacitance and increases the charge-transfer resistance. The inhibitor molecules first adsorb on the metal surface following a Langmuir adsorption isotherm. Both PEG and PVP offer good inhibition properties for mild steel and act as mixed-type inhibitors. Surface analysis by scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that PVP offers better protection than PEG.     

The litchi (Litchi Chinensis) peels extract as a potential green inhibitor in prevention of corrosion of mild steel in 0.5 M H2SO4 solution

The corrosion inhibition of mild steel in 0.5 M H₂SO₄ solution by the extract of litchi peel (Litchi chinensis) was studied by weight loss method, potentiodynamics polarization and electrochemical impedance spectroscopy (EIS). The results show that the litchi peels extract acts as mixed-type inhibitor. The inhibition of corrosion is found to be due to adsorption of the extract on metal surface, which is in conformity with Langmuir’s adsorption isotherm. UV–Vis, Fourier transform infrared (FT-IR) spectroscopy and Scanning electron microscopy (SEM) studies confirm that the inhibition of corrosion of mild steel occurs through adsorption of the inhibitor molecules.     

Inhibition of mild steel corrosion in 5 % HCl solution by 5-(2-hydroxyphenyl)-1,2,4-triazole-3-thione

A new corrosion inhibitor, namely 5-(2-hydroxyphenyl)-1,2,4-triazole-3-thione (5-HTT), has been synthesized and its influence on corrosion inhibition of mild steel in 5 % HCl solution has been studied using weight loss method and electrochemical measurements. Potentiodynamic polarization measurements clearly reveal that the investigated inhibitor is of mixed type, and it inhibits the corrosion of the steel by blocking the active site of the metal. Changes in impedance parameters were indicative of adsorption of 5-HTT on the metal surface, leading to the formation of protective films. The degree of the surface coverage of the adsorbed inhibitors was determined by weight loss measurements, and it was found that the adsorption of these inhibitors on the mild steel surface obeys the Langmuir adsorption isotherm. The effect of the temperature on the corrosion behavior with addition of 5 × 10^?4 M of the inhibitor was studied in the temperature range 30–60 °C. The reactivity of this compound was analyzed through theoretical calculations based on density functional theory to explain the different efficiency of these compounds as a corrosion inhibitor.     

Effect of Avogadro natural oil on the corrosion inhibition of mild steel in hydrochloric acid solution

The inhibition action of Avogadro natural oil on corrosion of mild steel in one molar hydrochloric acid solution was investigated by gravimetric and potentiodynamic polarization techniques. The surface morphology of as-corroded samples was assessed with high resolution scanning transmission electron microscopy equipped with energy dispersive spectroscopy (HR-STEM/EDS). From the results, the presence of Avogadro natural oil in the metal–acidic interface decreased the corrosion rate with all the exposure times. The inhibition efficiency (%IE) increases with the concentration of the inhibitor considered. Results obtained from gravimetric measurements indicate that the natural oil exhibited higher efficiencies of 93.26 % after 384 h of exposure time and 98.26 % recorded in the potentiodynamic polarization method, both at 4.5 g/v inhibitor addition. Equally, results from the linear polarization indicated higher potential value with an increase in the polarization resistance (R _p) and lower current density for the inhibited samples than the uninhibited mild steel sample. The inhibitive effect of this oil was explained in view of adsorption on the metal surface. The adsorption process follows the Langmuir adsorption isotherm.     

Corrosion inhibition behavior of cefuzonam at mild steel/HCl acid interface

The adsorption and corrosion inhibition behavior of cefuzonam (CZM) at mild steel surface were studied gravimetrically and electrochemically by using electrochemical impedance spectroscopy and Tafel polarization techniques. The increase in concentration and immersion time showed a positive effect. Inhibitor molecules directly adsorb on the surface on the basis of donor acceptor interactions between the p-electrons of benzene, sulfur and nitrogen atoms and the vacant d-orbital of iron atoms. The adsorption of CZM followed the Langmuir adsorption isotherm. A potentiodynamic polarization study revealed that CZM acted as mixed type of inhibitor. The results obtained from different methods are in good agreement. The adsorption behavior of CZM was experimentally investigated by contact angle measurement on metal surface. The contact angle of metal surface to the acid solution increased with inhibitor concentration, thereby confirming the increased hydrophobic nature of metal surface to the acid solution having the inhibitor.     

5-苯基-1H-四氮唑对铜片缓蚀性能的研究

通过金相显微镜和接触角测试研究了5-苯基-1H-四氮唑在硫-乙醇体系中对铜的缓蚀性能。结果显示,缓蚀剂可以在铜片表面形成疏水性保护膜,有效抑制了铜片的腐蚀。电化学测试表明,当缓蚀剂浓度为70 mg/L时缓蚀效率达到87%,对铜电极有明显的缓蚀作用。通过量子化学密度泛函理论研究了缓蚀剂分子结构与缓蚀性能的关系,分析了缓蚀剂分子的活性位点。通过分子动力学模拟研究了缓蚀剂分子在Cu的(111)表面的吸附行为。     

Ceforanide: a new and efficient corrosion inhibitor for mild steel in HCl solution

The corrosion inhibition properties of ceforanide for mild steel in HCl solution were analyzed by electrochemical impedance spectroscopy, potentiodynamic polarization, and gravimetric methods. The increase in inhibitor concentration and immersion time showed a positive effect on inhibition efficiency. The experimental data showed a frequency distribution and therefore a modeling element with frequency dispersion behavior and a constant phase element have been used. In aqueous acid solution, mild steel reacts by evolution of hydrogen. Visual observations showed that the hydrogen evolution decreased (i.e., corrosion inhibition effect increased) with increasing concentration of ceforanide. Potentiodynamic polarization study revealed that ceforanide acted as a mixed type of inhibitor. The results obtained from different methods are in good agreement. The adsorption behavior of ceforanide is experimentally investigated by contact angle measurement on metal surface. The contact angle of metal surface to the acid solution increased with inhibitor concentration; thereby confirming the increased hydrophobic nature of metal surface to the acid solution having inhibitors.     

Impedance spectroscopic study of corrosion inhibition of Al-Pure by organic Schiff base in hydrochloric acid

A new corrosion inhibitor namely o-Chloroaniline-N-benzylidene (o-CANB) has been synthesized and its inhibitive performance toward the corrosion of Al-Pure in 1.0 M hydrochloric acid has been investigated. Corrosion inhibition was studied by chemical method (weight loss) and electrochemical techniques including polarization method and electrochemical impedance spectroscopy (EIS). The present study has shown that this inhibitor is good in acidic media and the inhibition efficiency up to >99% in 1.0 M HCl. Polarization measurement revealed that the investigated inhibitor is a mixed type with a predominant action on cathode. Impedance measurement showed that the charge transfer resistance (R_ct) increased and double layer capacitance (C_dl) decreased with an increase in the inhibitor's concentration. Obtained results about inhibition efficiency from weight loss, polarization study and EIS are in good agreement with each other. The adsorption of the inhibitor on the metal surface in the acid solution was found to obey Langmuir's adsorption isotherm.     

Ficus carica extract as environmentally friendly inhibitor for the corrosion of L-80 carbon steel in 0.5 ​M ​H2SO4 media

We reported here, the corrosion inhibition of carbon steel (CS) in H₂SO₄ media by Ficus carica leaves extract as green sustainable inhibitor. This study was investigated using mass loss method (ML), potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM) and electrochemical impedance spectroscopy (EIS). As well as the metal surface morphology was analyzed by Atomic Force Microscopy (AFM). In addition, the chemical characterization of green inhibitor is carried out by Fourier Transform Infrared (FTIR). EIS revealed that the Ficus carica extract formed a thin protective film on the metal surface and by using of 300 ​ppm of extract of Ficus carica allow reaches (92.7%) of corrosion inhibition efficiency (CIE). The PDP curves revealed that the Ficus carica extract act as a mixed-type inhibitor. It was demonstrated that %IE enhanced with rising the Ficus carica extract doses also increased with arises in temperature (95.7%). Kinetic parameters and thermodynamic adsorption of the system have also been measured and studied. The data obtained revealed that the adsorption of Ficus carica on metal surface followed the Temkin isotherm and according to the activation energy (Ea1) the Ficus carica extract acts by chemisorption process. The results from unlike measurements were in a well accord.     

Inhibition effect of environmentally benign Karanj (Pongamia pinnata) seed extract on corrosion of mild steel in hydrochloric acid solution

The inhibition of the corrosion of mild steel in hydrochloric acid solution by the seed extract of Karanj (Pongamia pinnata) has been studied using weight loss, electrochemical impedance spectroscopy, potentiodynamic polarization, and linear polarization techniques. Inhibition was found to increase with increasing concentration of the extract. The effect of temperature, immersion time, and acid concentration on the corrosion behavior of mild steel in 1 M HCl with addition of extract was also studied. The adsorption of the extract on the mild steel surface obeyed the Langmuir adsorption isotherm. Values of inhibition efficiency calculated from weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy are in good agreement. Polarization curves showed that Karanj (P. pinnata) seed extract behaves as a mixed-type inhibitor in hydrochloric acid. The activation energy as well as other thermodynamic parameters for the inhibition process was calculated. The adsorbed film on mild steel surface containing Karanj (P. pinnata) seed extract inhibitor was also measured by Fourier transform infrared spectroscopy. The results obtained showed that the seed extract of Karanj (P. pinnata) could serve as an effective inhibitor of the corrosion of mild steel in hydrochloric acid media.     

Indole‐3‐acetic acid and N‐acetyltryptophan corrosion inhibition effects on mild steel in 1 M hydrochloric acid solution

Corrosion inhibition of indole‐3‐acetic acid and N‐acetyl tryptophan on carbon steel was investigated using polarization and electrochemical impedance spectroscopy (EIS). Polarization results revealed that corrosion inhibitors could reduce the rate of cathodic and anodic reactions on metal surface. EIS analysis showed inhibition efficiency of indoles increases by increasing the inhibitor concentration. The maximum inhibition efficiency was 97% and 80% in solutions containing 10 mM indole‐3‐acetic acid and 10 mM N‐acetyl tryptophan, respectively. The adsorption of inhibitors was found to follow Langmuir isotherm. Adsorption and film formation of inhibitors on the metal substrate were confirmed by calculating thermodynamic adsorption parameter (ΔG⁰_ads) and characterization of exposed metals' surface through contact angle measurements. Copyright © 2014 John Wiley & Sons, Ltd.     

5-Naphthylazo-8-hydroxyquinoline (5NA8HQ) as a novel corrosion inhibitor for mild steel in hydrochloric acid solution

In this study, 5-naphthylazo-8-hydroxyquinoline (5NA8HQ) was synthesized, characterized, and tested as a corrosion inhibitor for mild steel in 1 M HCl solution in the temperature range 20 to 50 °C. Weight-loss and potentiodynamic polarization measurements were used to analyse the corrosion behaviour of the metal in the absence and presence of different concentrations of the inhibitor. Analyses of surface film and inhibited solutions by FT-IR and UV–visible spectroscopy enabled us to clarify aspects of the inhibition mechanism. Further examination using X-ray diffraction confirmed the action of 5NA8HQ as an effective inhibitor of corrosion of mild steel in acidic media. The results obtained showed that this compound was a good inhibitor of corrosion. The inhibition is of mixed anodic–cathodic nature with predominance of anodic character. The Langmuir isotherm was found to accurately describe the adsorption behaviour of 5NA8HQ. Spectrophotometric analysis showed the formation of a layer at the surface of the corroded sample; this was interpreted as formation of complexes between 5NA8HQ and metal cations present in the steel structure.     

Electrochemical studies on the interaction of l-cysteine with metallic copper in sulfuric acid

Amino acids have been widely used as green corrosion inhibitors for an array of metals. Considering its importance in corrosion chemistry, studies were undertaken with the objective to discovering the inhibitory effect of a sulfur-containing amino acid, l-cysteine, on copper in different concentrations of sulfuric acid (0.5, 1.0, and 1.5 M) at different temperatures. Techniques like the weight loss method, electrochemical impedance spectroscopy, potentiodynamic polarization (Tafel), and adsorption studies were employed. Results revealed that l-cysteine do offer an attractive inhibition efficiency. However, with an increase in the concentration of the inhibitor, corrosion rates decreased irrespective of the temperature gradients. This is due to surface adsorption of the inhibitor molecules on the metal which has contributed to a decreased double-layer capacitance and increased polarization resistance. With the increase in the concentration of the medium, the corrosion rate was also enhanced and this is due the liberation of a high quantum of H⁺ ions. Based on the results of Tafel polarization studies, it is evident that the amino acid, l-cysteine, could act as a mixed type inhibitor. The importance of l-cysteine in the corrosion of copper metal has been highlighted in this paper.     

Employing electrochemical frequency modulation for studying corrosion and corrosion inhibition of copper in sodium chloride solutions

The inhibition effect of 2-carboxymethylthio-4-(p-methoxyphenyl)-6-oxo-1,6-dihy-dropyrimidine-5-carbonitrile (CPD) towards the corrosion of copper was studied in aerated stagnant 3.5% NaCl at 25 °C using ac techniques include electrochemical frequency modulation and electrochemical impedance spectroscopy as well as potentiodynamic polarization measurements. Corrosion rates determined using electrochemical frequency modulation (EFM) which measures the non-linear behaviour of a corroding system are compared with corrosion rates obtained from traditional electrochemical techniques and show good agreement. Data obtained from EIS were analyzed to model the corrosion inhibition process through equivalent circuit. Polarization measurements showed that CPD acts as mixed-type inhibitor. The inhibition efficiency increases with an increase in the concentration of CPD. The adsorption of the inhibitor on the copper surface in the sodium chloride solution was found to obey Langmuir’s adsorption isotherm. A mixed inhibition mechanism is proposed for the inhibitive effects of CPD as revealed by potentiodynamic polarization technique.     

Inhibition of steel corrosion by calcium benzoate adsorption in nitrate solutions: theoretical and experimental approaches

The inhibitive effects of calcium benzoate on steel corrosion were studied in sodium nitrate solutions at room temperature. Corrosion parameters of the steel/nitrate and steel/benzoate + nitrate interfaces were obtained from polarization curves. Adsorption parameters of benzoate on steel in sodium nitrate solutions were determined through changes in the degree of surface coverage by the inhibitor, as a function of concentration, time, and adsorption potential. The most likely adsorption configuration of benzoate on iron was envisaged with the help of semiempirical calculations such as extended Hückel calculations. A two-dimensional flat configuration was involving at least two metal atoms, one interacting with the phenolic group and the other with the carboxylate moiety. The effect of chloride on the corrosion inhibition of benzoate was analyzed by exposing the metal to different chloride solution concentrations, from which corrosion parameters were calculated and compared with those in nitrate solutions.     

Glutathione as green corrosion inhibitor for 6061Al-SiC(p) composite in HCl medium: electrochemical and theoretical investigation

This research deals with the inhibition activity of glutathione in 0.5 M HCl on the corrosion behavior of 6061Al-SiC_(p) composite. Glutathione is an eco-friendly water-soluble inhibitor. Polarization results reveal the cathodic inhibitor behavior of glutathione (Gt). The inhibition performance of Gt increases by increasing its concentration and lowering the medium temperature. The decrease in the corrosion current density and increase in inhibition efficiency on increasing Gt concentration reveal the attenuation of composite corrosion. Experimental results indicate the mixed adsorption with predominantly physisorption of Gt molecules adsorption on the composite surface following Langmuir adsorption isotherm. The impedance measurements indicate the rise in polarization resistance with an increase in Gt concentration, showing the control of composite corrosion. The surface analysis of the corroded and inhibited composite samples using a scanning electron microscope and atomic force microscope supports Gt molecules’ adsorption. The quantum chemical calculations confirm the conclusions of the experimental studies.

     

Experimental and theoretical studies of acridine orange as corrosion inhibitor for copper protection in acidic media

The corrosion process commonly limits the use of copper in practical applications. The use of corrosion inhibitors is one of the effective methods to reduce the corrosion rate of copper. In this research, the inhibition effect of acridine orange (3,6-bis(dimethylamine)acridine) (AcO) for the protection of copper in 0.5 ?M ?H₂SO₄ solution was studied. For this aim, the change of open circuit potential with exposure time (E_ocp-t), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), anodic and cathodic potentiodynamic polarization measurements (PP) and chronoamperometry (CA) techniques were used. Some quantum chemical parameters (E_HOMO, E_LUMO and dipole moment) were calculated and discussed. The AcO film formed over the copper surface was examined by SEM, EDX, AFM and contact angle measurements. The electrochemical data showed that AcO is an effective corrosion inhibitor even at low concentrations (ranging between 99.1% and %99.4 ?at concentrations from 0.01 ?mM to 1 ?mM). The corrosion rate of copper decreases in the presence of the inhibitor by reducing both anodic and cathodic rates, which is depended on its concentration. This compound behaves as mixed-type corrosion inhibitors with predominantly cathodic type. Its adsorption on the copper surface obeys Langmuir adsorption isotherm. The value of adsorption equilibrium constant (K_ads) and the standard free energy of adsorption were ΔG_ads 1.298 x 10³ ?M^?1 and -27.71 ?kJ/mol in the case of 0.5 ?M ?H₂SO₄ solution containing 1.0 ?mM AcO, which shows the adsorption is high and spontaneous. The adsorbed inhibitor film over the metal increase contact angle of the surface, which suggests the more hydrophobic properties of the surface are increasing coming from the orientation of hydrophobic sites to the electrolyte. The zero charge potential (E_pzc) studies showed that the surface charge of the metal is positive in the corrosive media containing the inhibitor. Quantum chemical calculations showed that the binding of inhibitor molecules to the metal surface takes place through N atoms of the inhibitor.     

Charge transfer resistance of nitro substituted dibenzalacetone on mild steel against acid attack

Corrosion of metals is a serious industrial problem due to its impact on economic losses and irresistible structural damage. In this work, dibenzalacetone derivatives 1, 5-bis (2-nitrophenyl)-1, 4- pentadien -3-one (BPDO) are employed as controlling agents on mild steel in 1 M H₂SO₄. The effect of BPDO on reducing corrosion of mild steel was analyzed using electrochemical and non-electrochemical methods. From experimental results, it is proved that the protection efficiency increases with enhance in BPDO concentration and diminishes with enlarge in temperature. BPDO is an effective corrosion inhibitor with a 98.64% inhibition efficiency at only 300 ppm concentration. IE diminishes as exposure time increases due to a decrease in the stability of the adsorbed BPDO on the metal surface. The results of Tafel polarization measurements revealed that BPDO acts as a mixed type inhibitor. In both the polarization and Electrochemical Impedance tests, 308K and 300 ppm of BPDO were used, yielding maximal inhibition efficiencies of 98.41% and 97.57% respectively. Langmuir adsorption isotherm is found to be the most suitable way to explain the adsorption of BPDO on the surface of mild steel. Physisorption is proposed from the values of ΔG_ads. Formation of a protective layer on mild steel surface was affirmed by various spectroscopic studies.     

Inhibition effect of 1,3,5-tri-p-tolyl-1,3,5-triazene on the corrosion of brass in 0.5 M HCl solution

1,3,5-tri-p-tolyl-1,3,5-triazene was investigated as a corrosion inhibitor for brass in 0.5 M HCl solution using weight loss, potentiodynamic polarization, linear polarization resistance and electrochemical impedance spectroscopy. Data obtained from these methods showed average inhibition efficiency (76 %) at optimum concentration. The adsorption of the inhibitor on the brass surface follows the Frumkin adsorption isotherm.