Corrosion inhibition of mild steel in acidic media using newly synthesized heterocyclic organic molecules

Hydrogen evolution reaction (HER) (cathodic reaction) of mild steel immersed in H₂SO₄ acid was investigated. Electrochemical corrosion behavior and hydrogen evolution reaction of mild steel has been investigated using different electrochemical techniques. Steel was polarized vs. saturated calomel electrode (SCE) in naturally aerated 1.0 M H₂SO₄ aqueous solution containing four organic inhibitors (newly synthesized heterocyclic compounds) of different concentrations. The observed different influence of corrosion inhibitors on the hydrogen evolution reaction was associated with the different chemical composition and structure. Polarization results showed that corrosion current density, i_corr, and hydrogen evolution decreases with increasing concentration of inhibitors in 1.0 M H₂SO₄, indicating a decrease in the corrosion rate. Electrochemical impedance spectroscopy (EIS) measurements confirmed this behavior. An increase of temperature leads to increase in the corrosion or hydrogen evolution rate and a decrease of the total resistance value, R_T. The obtained results were confirmed by surface examination.     

Electrochemical investigation on the corrosion and hydrogen evolution rate of mild steel in sulphuric acid solution

Corrosion and hydrogen evolution rate of mild steel alloy have been investigated using various electrochemical techniques. Mild steel was polarized vs. saturated calomel electrode (SCE) in naturally aerated 0.1 M H₂SO₄ solution containing three newly synthesized heterocyclic compounds in different concentrations. The data obtained from polarization technique showed that the corrosion current density, i_corr, and the hydrogen evolution rate decrease with increasing concentration of heterocyclic inhibitors in 0.1 M H₂SO₄ medium, indicating a decrease in the corrosion rate of mild steel as well as an increase in the inhibition efficiency (IE) of the newly synthesized inhibitors. The impedance measurements confirmed well the polarization behaviour. Increasing the temperature leads to an increase in corrosion or hydrogen evolution rate of the mild steel and a decrease of the total resistance value (R_T) or the relative thickness (1/C_T) of the film. The obtained results were confirmed by surface examination using scanning electron microscope.     

Influence of cerium (III) ions on corrosion and hydrogen evolution of carbon steel in acid solutions

This paper intended to investigate the influence of rare earth Ce(III) ions on the corrosion behavior of carbon steel in two acid solutions (0.5 M HCl and 0.25 M H₂SO₄) in order to control the rate of hydrogen evolution in those systems. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used for corrosion rate and electrochemical impedance evaluation. SEM was used to examine the sample surfaces immersed in acid solutions containing the optimal threshold Ce(III) concentration (0.1 mM). All results reveal that the corrosion resistance of carbon steel in HCl is superior to that in H₂SO₄ due to the higher rate of hydrogen production in the latter. A model for the corrosion process mechanism and inhibition by Ce(III) salt for carbon steel in the two tested media is proposed.     

Hydrogen generation during the corrosion of carbon steel in crotonic acid and using some organic surfactants to control hydrogen evolution

The purpose of this paper is to describe and evaluate the corrosion of carbon steel in crotonic acid for hydrogen production and using polysorbate 20 (NS), dioctyl sodium sulfosuccinate (AS) and benzalkonium chloride (CS) to control hydrogen evolution. Measurements were conducted in tested solutions using hydrogen evolution and electrochemical impedance spectroscopy (EIS) measurements and complemented by scan electron microscope (SEM) and energy dispersive X-ray (EDX) investigations. It is shown that the hydrogen generation rate obtained during the corrosion of carbon steel in crotonic acid increased with increase in acid concentration, temperature and immersion time. The addition of organic surfactants inhibits the hydrogen generation rate. The inhibition occurs through adsorption of organic surfactants on the metal surface. Adsorption processes followed the Langmuir isotherm. The order of effectiveness of the surfactants was AS > NS > CS. The values of activation energy (E_a) and heat of adsorption (Q_ads) were calculated and discussed.     

Influence of 2-(4-chlorophenyl)-2-oxoethyl benzoate on the hydrogen evolution and corrosion inhibition of 18 Ni 250 grade weld aged maraging steel in 1.0 M sulfuric acid medium

Electrochemical corrosion behavior and hydrogen evolution reaction of weld aged maraging steel have been investigated, in 1.0 M sulfuric acid solution containing different concentrations of 2-(4-chlorophenyl)-2-oxoethyl benzoate (CPOB). The data obtained from polarization technique showed that the corrosion current density (i_corr) and the hydrogen evolution rate decrease, indicating a decrease in the corrosion rate of weld aged maraging steel as well as an increase in the inhibition efficiency (η%) with the increase in inhibitor concentration. Changes in impedance parameters were indicative of adsorption of CPOB on the metal surface, leading to the formation of protective film. Both activation (E_a) and thermodynamic parameters (ΔG_ads⁰, ΔH_ads⁰ and ΔS_ads⁰) were calculated and discussed. The adsorption of CPOB on the weld aged maraging steel surface obeyed the Langmuir adsorption isotherm model. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) study confirmed the formation of an adsorbed protective film on the metal surface.     

Inhibition effect of newly synthesized heterocyclic organic molecules on corrosion of steel in alkaline medium containing chloride

Two new organic compounds were tested experimentally as inhibitors for mild steel in NaOH in presence of NaCl by electrochemical and hydrogen evolution techniques. Results demonstrated that the two inhibitors show an adsorption on steel surface according to Langmuir adsorption isotherm. The inhibition efficiency increases with increasing inhibitor concentrations to attain a maximum value at 1.0 mM for compound I and at 6.0 mM for compound II, respectively. The results were confirmed by surface examination via scanning electron microscope.     

Tracing the influence of small additions of antimony to zinc on the hydrogen evolution and anodic dissolution processes of zinc as anodes for alkaline batteries application

The processes of hydrogen evolution reaction and anodic dissolution of zinc and zinc-antimony alloys with different antimony amounts (0.5 and 1%) immersed in 6 M KOH were tested via many electrochemical methods as Tafel polarization, cyclic voltammetry (CV), impedance spectroscopy (EIS), and charge-discharge. Newly formed phases, the morphology of the surface, and chemical composition for Zn and Zn–Sb alloys after and before corrosion were determined via appreciated analysis instruments as X-ray diffraction (XRD), scanning electron microscopy (SEM) provided with an energy-dispersive X-ray spectroscopy detector (EDS). The results of Tafel plots exhibited that, the protection efficiency of corrosion (η%) gets greater with the increase of both temperature and Sb content. It is impressive to note that, η% for Zn–Sb alloy (1%Sb) reaches the highest value of 98.55% at the higher studied temperature (55 °C). The potential of corrosion (E_corr.) is shifted to a more negative position with the increase of antimony addition to zinc. This reveals that minor alloying amounts of Sb with Zn plays an important role to improve the suppression of the evolved hydrogen, charge efficiency, capacitance, and lifetime of alkaline batteries. Surface investigations revealed the presence of ZnSb and Zn₄Sb₃ phases on the alloy surface have an essential function in the protection of zinc anodes, and improvement of charge-discharge.     

The hydrogen evolution reaction on nickel-polyaniline composite electrodes

The electrolytic codeposition of nickel composite coatings with different amounts of polyaniline particles (PAni) was used to produce electrodes for the catalytic hydrogen evolution reaction (HER). The electrodes produced were imaged by scanning electron microscopy, and their catalytic activities for HER were determined by linear Tafel polarization and electrochemical impedance spectroscopy (EIS) in a 0.5 M H₂SO₄ solution. The electron micrographs showed that the amount of exposed polyaniline surface was directly related to the polyaniline concentration in the solution used for the electrolytic codeposition. The linear Tafel polarizations indicated that the HER was limited by the Volmer step, and the EIS measurements showed that the presence of PAni on the electrode surface affected the HER. Electrodes with higher composite contents exhibited enhanced catalytic activity.     

Analysis of corrosion inhibition of Kleinhovia hospita plant extract aided by quantification of hydrogen evolution using a GLCM/SVM method

During a corrosion inhibition test, a combination of common electrochemical corrosion test methods with an in-situ quantification of H₂ evolution could provide a comprehensive analysis of the effectiveness of an organic inhibitor. This work analyzes the corrosion inhibition efficiency of Kleinhovia hospita plant extract on carbon steel specimens polarized in 1 M HCl, based on acquired H₂ bubbles images, by using gray level co-occurrence matrix (GLCM) and support vector machine (SVM) classification. A conformity was established between the classified-algorithm models and the corrosion test results obtained by potentiodynamic polarization test and electrochemical impedance spectroscopy. Hydrogen rate and corrosion rate show the same lowest trends at the addition of 3000 mg/L of KH extract. The inhibitor addition led to 99% of maximum inhibition efficiency. Based on the polarization data, KH extract is a mixed type inhibitor. Supported by Langmuir calculation for adsorption isotherm, a physisorption is stated as the main inhibition mechanism. The feature extraction using GLCM was able to distinguish changes in H₂ bubbles characteristics where the addition of inhibitor affected the corrosion rate. The GLCM/SVM method applied as a linear kernel function and showed 88% accuracy with d = 5 for image data testing. Remarkable changes in H₂ gas bubbles characteristic were observed in the specimen immersed in the solution with 3000 mg/L inhibitor addition, signified by 99% inhibition efficiency.     

Evaluation of the electrocatalytic properties of Tungsten electrode towards hydrogen evolution reaction in acidic solutions

Hydrogen has concerned interest universally as an environmentally nontoxic and renewable fuel. Electrocatalytic hydrogen evolution reaction (HER) is one of the utmost favorable methods for hydrogen creation on a vast scale; however, the high cost of Pt-based supplies, which demonstrate the highest activity for HER, forced investigators to look for cheaper electro-catalysts. Tungsten has been considered as an effective, active and low cost electrocatalyst for the hydrogen evolution reaction, mostly in alkaline media, and we have investigated here its behavior in acid electrolytes. HER has been studied utilizing linear polarization technique and electrochemical impedance spectroscopy (EIS). It happens on W at rather low overpotential (−0.32 V vs. NHE at 10 mA cm⁻², in 0.5 M H₂SO₄), yet more cathodic than the widely used Pt/C catalyst, but not so far from more sophisticated systems developed recently. The effect of acid concentration on the HER rate and the electrode stability was investigated. Cathodic transfer coefficient and exchange current density were calculated for the HER from Tafel curves obtained in H₂SO₄ solution at concentrations ranging from 0.1 to 3.0 M. EIS experiments were performed under both open circuit and/or cathodic polarization. It was found that the hydrogen evolution rate is relatively high under low overpotential, confirming that W is a possible applicant to substitute more expensive electrocatalysts usually used for the HER under acidic conditions. The process is economic and appropriate with no need for specific treatments, as supported by additional X-ray diffraction (XRD), Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) characterization of the tungsten electrode surface.     

Lead cathodes functionalized with magnetite particles with enhanced electrocatalytic activity for hydrogen evolution reaction in sulfuric acid solutions

The generation of molecular hydrogen through the electrochemical water splitting process has been extensively studied, due to the potential application of hydrogen to produce green energy with fuel cells. Researchers have been focused in the synthesis of electrocatalysts for the hydrogen evolution. The accumulative roll bonding (ARB) is a promising method which can process a large quantity of an electrode for industrial demand. In this research the ARB process is employed to synthesize lead base electrodes functionalized with magnetite particles (Fe₃O₄) to evaluate their electrocatalytic properties on the hydrogen evolution reaction (HER) in sulfuric acid solutions. SEM, EDS and FESEM techniques are used to characterize the functionalized lead cathodes. The effect of rolling passes, magnetite concentration, and suspended magnetite particles on the HER kinetics is studied using linear voltammetry, Tafel plots, and electrochemical impedance spectroscopy (EIS). The results revealed that lead cathodes functionalized with magnetite present great advantages over lead cathodes, such as: a decrease of 0.37 V in HER over-potential, an increase of 84.3 times in the exchange current density, a decrease in the charge transfer resistance of 98%. From a mechanistic viewpoint, HER is catalyzed by the presence of Fe²⁺ adsorbed on the lead cathode; ferrous ions are produced from the reductive dissolution of magnetite particles. Long-term electrolysis and multiple cyclic voltammetry tests (800 polarization cycles) revealed that the catalytic effect is maintained during 44 h of operation. According to the Tafel curves and EIS results, the Volmer reaction is the rate determining step of the HER on these functionalized cathodes.     

Effect of minor nickel alloying with zinc on the electrochemical and corrosion behavior of zinc in alkaline solution

The electrochemical and corrosion behavior of pure zinc and Zn-0.5Ni alloy in strong alkaline solution (7 M KOH) was investigated by Tafel plot, potentiodynamic, potentiostatic and electrochemical impedance spectroscopy (EIS) methods, and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Measurements were conducted under different experimental conditions. The results of both Tafel plot extrapolation and the electrochemical impedance spectroscopy (EIS) measurements exhibited the same trend, which the cathodic and anodic processes on the alloy surface are less significant compared with those on the pure zinc. The results revealed that, the shift in steady state of open-circuit potential (E_corr) to more negative potential in the case of the studied alloy compared with that of pure zinc has a positive effect on both charge efficiency and self-discharge.The anodic potentiodynamic measurements demonstrated that the polarization curves exhibited active/passive transition. The active dissolution of both pure zinc and its alloy increases with increasing temperature and scan rate. The activation energy (E_a) value of active region and peak current (I_AI) of the two studied electrodes in the investigated alkaline solution is calculated and compared. In the case of alloy, the results obtained at certain positive potential (+425 mV vs. SCE), exhibited high current density indicating that the most passive layer was destroyed. This indicates that the addition of small amount from Ni to Zn promotes the electrochemical reaction (in the passive region), acting as so-called self catalysis. Accordingly, one can conclude that, the electrochemical behavior of the investigated alloy in strong alkaline solution contributes to suppression of hydrogen gas evolution and increases the corrosion resistance. In addition, reactivation of the alloy surface takes place in the passive region.     

Electrocatalytic properties of porous Ni-Co-WC composite electrode toward hydrogen evolution reaction in acid medium

Porous Ni-Co-(WC)_x ternary composite electrodes were fabricated by means of electrodeposition on a foam Ni substrate. The surface morphology and microstructure of the electrodes were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrocatalytic properties of porous Ni-Co-(WC)_x electrodes for hydrogen evolution reaction (HER) in 0.5 M H₂SO₄ solution at temperatures from 25 to 50 °C were conducted by means of cathodic polarization, electrochemical impedance spectroscopy (EIS), cyclic voltammetry and chronoamperometry (CA). These Ni-Co-WC electrodes are efficient electrocatalysts for HER. Compared with the porous Ni-Co electrode, the porous Ni-Co-(WC)_x electrode exhibited a lower HER overpotential, a lower electrochemical impedance, a lower apparent activation energy and a higher exchange current density. The apparent exchange current density of porous Ni-Co-(WC)_x (x = 10, 20, 30 and 40 g/l) is 2.01, 3.01, 7.8 and 19.91 times of porous Ni-Co electrode, respectively. With the increase of WC concentration and temperature, the apparent exchange current density of HER was enhanced. With the increase of WC concentration and potential, the HER resistance and the activation energy decreased. The Ni-Co-(WC_)x electrode exhibited superior corrosion resistance and stability for HER.     

Effect of Sn and Zn alloying with Al on its electrochemical performance in an alkaline media containing CO2 for Al-air batteries application

Aluminum alloyed with other metals, such as Sn and Zn, was synthesized via fusion to trace the impact of alloying elements on the electrochemical characteristics of Al anodes. The corrosion inhibition and electrochemical tests were performed in a 5 M KOH medium in the absence and presence of CO₂ for the Al–Sn, and Al–Zn anodes and compared to the commercial aluminum. Tafel polarization exhibited that the anodic and cathodic branches display lower current densities than Al metal in pure KOH. The steady state of the open circuit voltage (E_corr.) for the studied alloys was shifted to a more negative magnitude than for Al. The corrosion current is sharply decreased, and potential is significantly shifted to less negative values in the presence of CO₂. This is due to forming of a protective layer from the carbonate of Al, Sn, and Zn on the surface. Amazing results were obtained and discussed in the case of CO₂. Electrochemical impedance spectroscopy (EIS) results exhibited that charge transfer resistance (R_ct) values rise with alloying elements. The data of Tafel plots are consistent with those of EIS. The alloying of Al with Sn and Zn elements significantly affects capacitance, hydrogen evolution process suppression, and charge-discharge efficiency. This reveals that the highest potential value in the presence of CO₂ in the charging process is obtained for Al–Zn alloy, while the most negative potential is obtained for Al in the discharging process with CO₂. Moreover, the discharge time is higher in the alloys than in commercial Al in the absence and more in the presence of CO₂. The produced alloys are thought to provide good anodes for long-life rechargeable batteries.     

Influences of temperature, H2SO4 concentration and Sn content on corrosion behaviors of PbSn alloy in sulfuric acid solution

The influences of temperature, H₂SO₄ concentration and Sn content on corrosion behaviors of PbSn alloys in sulfuric acid solution were investigated by potentiodynamic curve, cyclic voltammetry (CV), linear sweeping voltage (LSV), electrochemical impedance spectra (EIS), a.c. voltammetry (ACV) and Mott-Schottky analysis. The microstructure of the corrosion layer on PbSn alloy was analyzed by scanning electron microscopy (SEM). The results showed that the corrosion resistance of PbSn alloy increased with ascending Sn content and H₂SO₄ concentration, the increment of temperature can decrease the corrosion resistance of PbSn alloy in H₂SO₄ solution. The conductivity of the anodic film on PbSn alloy was enhanced with increasing temperature, ascending Sn content and descending H₂SO₄ concentration. SEM result revealed that the corrosion film after cyclic voltammetry was consisted of tetragonal crystal, the porosity enlarged with decreasing temperature, Sn content and H₂SO₄ concentration.     

Investigation on the corrosion and hydrogen evolution for AZ91D magnesium alloy in single and anion-containing oxalate solutions

Corrosion characterization of AZ91D alloy was studied in aqueous sodium oxalate solutions with various concentrations using different electrochemical techniques (open circuit potential, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV)). The corrosion rate and consequently the rate and extent of hydrogen evolution were found to increase significantly with increasing oxalate anion concentration and temperature or with decreasing the pH of solution. Increasing additions of various anions over the lower concentration range (0.001-1.0 mM) in the blank oxalate solution increases to a varying extent the corrosion rate of the alloy and hence increases the hydrogen evolution rate and decreases surface film stability in the following order Cl⁻ > SO₄²⁻ > F⁻. On the other hand, addition of phosphate anion exhibits a reverse trend, where the active corrosion rate decreases with increasing PO₄³⁻ anion concentration, implying that this anion acts as a passivator for AZ91D alloy. The obtained electrochemical results are further confirmed by scanning electron microscopy (SEM) analysis.     

Effect of corrosion inhibitors on hydrogen uptake by Al from NaOH solution

Corrosion rate, hydrogen permeation rate (hydrogen uptake) and stress corrosion cracking of Al were studied in NaOH solutions, pure and with the addition of H₃BO₃, EDTA, KMnO₄ and As₂O₃. The presence of the studied species in electrolyte and the implantation of Al surface with B⁺ ions inhibited corrosion. Hydrogen uptake was found to be promoted or inhibited by means of studied species, depending on the method of their introduction into the base solution and on the applied polarization. The observed different influence of corrosion inhibitors on the hydrogen uptake was associated with the different chemical composition and structure (revealed by XPS analysis) of the surface films, formed on Al under the various conditions. Under similar polarization conditions, the presence of H₃BO₃ in the base solution similarly affected the hydrogen uptake by Al and the susceptibility to stress corrosion cracking of the metal.     

Electrochemical determination of niobium cathode as an efficient electrocatalyst for hydrogen generation in acidic media

Hydrogen gas (H₂) is notified as a renewable energy carrier. It is wanted to discover a low-cost electrocatalyst for the hydrogen evolution reaction (HER) to substitute the high-cost Pt in electrolysis cell. Niobium electrocatalyst nominated to substitute noble materials for electrocatalytic H₂ production and its electrochemical manner was estimated in H₂SO₄ acid of various concentrations utilizing a steady-state polarization and electrochemical impedance spectroscopy (EIS). The influences of acid concentration, cathodic potential and temperature on the H₂ creation were examined. The outcomes display that HER on Nb electrode proceeds by the Volmer-Heyrovsky mechanism. EIS tests, under open circuit and under cathodic polarization, were performed and the fitting has been done utilizing a suggested model for the electrode/electrolyte interface. Apparent activation energies (E_a) were estimated to be ca. 10.5 kJ mol^?1 for the HER on Nb. Thus, Nb is a good electrocatalyst for the cathodic H₂ manufacturing.     

Inhibition effect of natural polysaccharide composite on hydrogen evolution and P110 steel corrosion in 3.5 wt% NaCl solution saturated with CO2: Combination of experimental and surface analysis

For the analysis of corrosion and hydrogen production inhibition, we have synthesized Guar gum and methylmethacrylate (GG-MMA) composite. The synthesized composite was used as an eco-friendly corrosion inhibitor for P110 steel in 3.5% NaCl solution saturated with carbon dioxide at 50 °C. The primary corrosion techniques like weight loss, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) was used to analyze the corrosion inhibition process. EIS study reveals the kinetically controlled corrosion inhibition process. The results of PDP proposed that GG-MMA composite is the cathodic type of inhibitor. The corrosion inhibition performance of GG-MMA alone is 90% at 400 mg/L, and that of formulation with KI (5 mM) + GG-MMA (300 mg/L) is 96.8%. The adsorption of GG-MMA over P110 steel is spontaneous and mixed type i.e., both physical and chemical. The conformation of GG-MMA molecule adsorption was done using a scanning electron microscope (SEM), Contact angle measurement, Atomic force microscopy (AFM), Scanning Electrochemical Microscopy (SECM) and X-ray photoelectron spectroscopy studies.     

Electrochemical behavior and application of lead–lanthanum alloys for positive grids of lead-acid batteries

The effects of different lanthanum content (0, 0.00600, 0.0112, 0.0195 and 0.0540 wt.%) on the electrochemical behavior of lead–lanthanum alloy in sulfuric acid solutions were investigated by linear potential sweep (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The morphology of the corrosion layer and corrosion section of Pb and Pb–La alloys were analyzed by scanning electron microscope (SEM) after corrosion testing. It was found that the addition of La inhibits the oxygen evolution reaction on the surface of Pb alloy electrodes, and La amounts of 0.00600 and 0.0540 wt.% in Pb–La alloy electrodes can lead to a more effective inhibition. The results of the LSV, CV and EIS experiments show that the addition of La can inhibit the growth of the anodic Pb(II) oxides and PbO₂ film. The resistance of the anodic film on the Pb–La electrodes is much lower than that on the Pb electrode. SEM for the corrosion layer indicates that the corrosion product on pure Pb and Pb–0.0195% La alloy is uniform and compact. The corrosion products on the alloys with La contents of 0.00600, 0.0112 and 0.0540 are loose and porous that the active materials can easily sit in the apertures to contact the grid surface intimately with the effective. The results demonstrate that Pb–La alloys show the potential for application as the positive grid material in maintenance-free lead-acid batteries.