Gülfeza Kardaş

Adsorption and Corrosion Inhibition Effect of 1,1′-Thiocarbonyldiimidazole on Mild Steel in H2SO4 Solution and Synergistic Effect of Iodide Ion

Abstract The inhibition effect of 1,1′-thiocarbonyldiimidazole (TCDI) on the corrosion behaviors of mild steel (MS) in 0.5 mol·L−1 H2SO4 solution was studied with the help of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR) techniques. The effect of immersion time on the inhibition effect of TCDI was also investigated over 72 h. For the long-term tests, hydrogen evolution with immersion time (VH2–t) was measured in addition to the three techniques already mentioned. The thermodynamic parameters, such as adsorption equilibrium constant (Kads) and adsorption free energy (ΔGads) values, were calculated and discussed. To clarify inhibition mechanism, the synergistic effect of iodide ion was also investigated. The potential of zero charge (PZC) of the MS was studied by electrochemical impedance spectroscopy method, and a mechanism of adsorption process was proposed. It was demonstrated that inhibition efficiency increased with the increase in TCDI concentration and synergistically increased in the presence of KI. The inhibition efficiency was discussed in terms of adsorption of inhibitor molecules on the metal surface and protective film formation.

Electrochemical Investigation of Barbiturates as Green Corrosion Inhibitors for Mild Steel Protection

Barbituric Acid (BA), Ethyl Barbituric Acid (EBA) and 2-Thiobarbituric Acid (2-TBA) were studied as inhibitors for mild steel (MS) corrosion in 0.5 Μ HCl solution. Electrochemical studies were performed by means of electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. Inhibition efficiency of these compounds is dependent upon structure and inhibitor concentration. 2-TBA is a better inhibitor than the others. The inhibition efficiency of 2-TBA increases with increase of inhibitor concentration and reached 97.7 % at 168 hours. 2-TBA adsorbs on MS surface according to the Langmiur adsorption isotherm. The values of adsorption equilibrium constant ( K a d s ) and standard free energy of adsorption (AG° a ( / s ) were calculated and discussed. To evaluate adsorption mechanism of inhibitor on the steel surface, the potential of zero charge (pzc) of MS was also determined by EIS method.

The Rhodanine inhibition effect on the corrosion of a mild steel in acid along the exposure time

The corrosion performance of a mild steel (MS) exposed to a 0.5 M HCl solution with various concentrations of Rhodanine (Rh) was studied by means of anodic and cathodic voltammetric curves, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. Rh makes the corrosion of MS in HCl solution decelerate with the exposure time so as to reach a protective value of more than 99% in 168 h. The adsorption of Rh molecules on the MS obeys Langmiur adsorption isotherm. Thermodynamic parameters, adsorption equilibrium constant (Kads), and standard free energy of adsorption (ΔGadso) were calculated and discussed. The high inhibition efficiency was discussed in terms of blockading the metal surface by the Rh molecules strongly adsorbing witch their active centers and thus forming a sufficiently effective protective film.

Electrocatalytic oxidation of methanol on Pt/NiZn electrode in alkaline medium

In this study, a platinum electrode was coated with NiZn layer (Pt/NiZn) in a nickel-zinc bath by electrodeposition for use as anode material for methanol electrooxidation in alkaline solution. The electrode prepared was etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the methanol electrooxidation (Pt/NiZn). The surface morphologies and compositions of coating before and after alkaline leaching were determined by energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) techniques. The effect of NiZn coated platinum electrode for methanol electrooxidation was investigated in 1 M NaOH solution by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Methanol electrooxidation on Pt/NiZn electrode was studied at various temperatures and potential scan rates. The results showed that Pt/NiZn electrode behaved as an efficient catalyst for the electrooxidation of methanol in alkaline medium.

Investigation of adsorption and corrosion inhibition effect of 1,1’-thiocarbonyldiimidazole on mild steel in hydrochloric acid solution

The adsorption and inhibition effect of 1,1′-thiocarbonyldiimidazole (TCDI) on the corrosion of mild steel (MS) in 0.5 M HCl solution was studied in both short and long immersion time (120 h) with the help of electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. For long-time tests, the hydrogen gas evolution (VH2-t) and the change of open circuit potential with immersion time (Eocp-t) were also utilized in addition to the former two techniques. The surface morphology of MS after its exposure to 0.5 M HCl solution with and without 1.0 × 10−2 M TCDI was examined by scanning electron microscopy (SEM). It was demonstrated that the inhibition efficiency of studied inhibitor is concentration depended and increased with TCDI concentration. The higher value of inhibition efficiency was obtained after longer immersion time merely on the basis of strong increase of corrosion rate of mild steel in the blank solution. The high inhibition efficiency was discussed in terms of adsorption of inhibitor molecules and protective film formation on the mild steel surface which was substantiated by SEM micrographs. The adsorption of TCDI on MS was found to obey Langmuir adsorption isotherm.

Cobalt-modified nickel–zinc catalyst for electrooxidation of methanol in alkaline medium

Cobalt-modified nickel-zinc catalyst CuNi(Zn)Co is prepared on a copper substrate by using electrodeposition. Its catalytic efficiency for methanol oxidation is studied with cyclic voltammetry, chronoamperometry, and chronopotentiometry techniques. The surface morphology and chemical composition of catalyst are characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The oxidation kinetic parameters activation energy (Ea), active species on the surface (Γ), and rate constant (k) are determined from cyclic voltammograms which are performed at different methanol concentrations and temperatures. The results show that Ni(Zn)Co catalyst has higher catalytic activity than Ni, Co, and NiZn coatings as a composite catalyst for a promising choice of methanol electrooxidation in the alkaline medium.

Anodizing and corrosion behaviour of aluminium

In this study, aluminum was anodized in 0.4 M H2SO4 + 0.145 M H3BO3 solution by means of potentiostatic method. In first step, the most appropriate conditions (anodizing voltage and period) were determined. The voltage-current behavior was investigated between 0 to 30 V and oxide formation potential (15 V) was determined. Then chorono-amperometric measurement was obtained at this potential during 2 hours. Therefore, anodizing process was applied at 15 V between aluminium anode and mild steel cathode. In the second step, the corrosion performance of non-anodized (Al) and anodized samples (Al2O3) have been investigated in 3.5% NaCl solution by using electrochemical impedance spectroscopy and polarization techniques. The interface between metal and solution was modeled with the equivalent circuit successfully. The circuit’s elements were calculated with Ivium Soft fitting program. The polarization curves were obtained between −1.8 V and 0.5 V potential ranges. The experimental results proved that the thickness and quality of oxide film was improved with help of anodizing process. Thus the corrosion resistance of anodized aluminum is significantly increased.

Effect of some primary alcohols on hydrogen yield on platinum cathode in chloride solution

Abstract The effect of some primary alcohols on hydrogen evolution has been studied in 0.01 M NaCl +1 M x alcohol (x: 0, methyl, ethyl and propyl alcohol) at different pHs (3, 5 and 8) and temperatures (25°C,50°C and 75°C) on Pt electrode at a constant potential (5.00 V ) using electrolysis. The theoretical (Erev) and experimental discharge (Eexp) potentials for these systems have been determined and the volume of hydrogen gas measured at periods of time. The yield of hydrogen gas was calculated for different temperatures. For this system, alcohol adsorbs on to the platinum surface in alcohol solutions and decreases the overpotential for anodic and cathodic reactions; so that the highest hydrogen yield is obtained in all alcohol solutions.

The experimental and quantum chemical investigation for two isomeric compounds as aminopyrazine and 2-amino-pyrimidine against mild steel corrosion

Purpose The purpose of this paper is to investigate the adsorption and corrosion inhibition of two isomeric compounds (C4H5N3) as aminopyrazine (AP) and 2-amino-pyrimidine (2AP) on mild steel (MS) in 0.5 M HCl. The study was a trial to combine experimental and modelling studies and research effect of molecular geometry on inhibition effect of inhibitor molecules. Design/methodology/approach The thermodynamic, kinetic and quantum parameters were determined. The electrochemical impedance spectroscopy and anodic polarisation measurements were obtained. The scanning electron microscope was used for monitoring electrode surface. The highest occupied molecular orbital, energy of the lowest unoccupied molecular orbital, Mulliken and natural bonding orbital charges on the backbone atoms, absolute electronegativity, absolute hardness were calculated by density functional theory (DFT)/B3LYP/6-311G (++ d,p). Findings Results showed that AP and 2AP suppressed the corrosion rate of MS. The corrosion current values were 0.530, 0.050 and 0.016 mA cm-2 in HCl, AP and 2AP containing HCl solutions, respectively. It was illustrated with the blocked fraction of the MS surface by adsorption of inhibitors which obeyed the Langmuir isotherm. The inhibition efficiency follows the order: 2AP > AP which is in agreement with experimental and quantum results. Originality/value This paper provides lay a bridge on the molecular geometry and inhibition efficiency by electrochemical tests and modelling study. The inhibition effect of AP and 2AP has not been compared with each other, neither experimentally nor theoretically. This study put forward possible application of 2AP as corrosion inhibitor especially for closed-circuit systems.

2.12 Electrolytic Materials

Electrolyte is the part of the electrochemical cell consists of an anode, a cathode, and an electrolyte which provide the completion of the reactions occurring at the surface of these two electrodes. Electrolytes that are responsible for conducting the electricity via ions can be used in different forms according to the system conditions. When selecting the type of electrolyte to be used, the compatibility with the working conditions should be examined in detail analyzing many parameters, such as the stability of the electrolyte, the reactivity against anode and cathode, the electrical conductivity, the ionic conductivity, the solution resistance, and the volatility.