Mechanism of inhibition of electrode reactions at high surface coverages - II
TL;DR: In this article, the inhibition of Cu 2+, Cd 2+ and Zn 2+ discharge reactions was studied in the presence of C 4 -C 6 alcohols, phenol, benzyl alcohol and cyclohexanol (SAS).
Abstract: The inhibition of Cu 2+ , Cd 2+ and Zn 2+ discharge reactions was studied in the presence of C 4 –C 6 alcohols, phenol, benzyl alcohol and cyclohexanol (SAS) in 0.5 M Na 2 SO 4 + 1 mM H 2 SO 4 supporting electrolyte. It is found from the results that at high surface coverages by SAS, the inhibition is due to “sieve effect” which is different from that at low coverages. The true standard rate constant is proportional to exp[(− N Δγ A i )/( RT )] where Δγ A i is the extra energy (in the form of work) that must be done in order to create a free area required for a discharge reaction.
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TL;DR: In this article, 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole (4-MTHT) has been studied for corrosion inhibition of mild steel in 1 M HCl and 0.5 M sulphuric acid (H 2 SO 4 ).
Abstract: The efficiency of a new triazole derivative, namely, 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole (4-MTHT) has been studied for corrosion inhibition of mild steel in 1 M hydrochloric acid (HCl) and 0.5 M sulphuric acid (H 2 SO 4 ). Corrosion inhibition was studied using electrochemical methods and weight loss measurements. These studies have shown that 4-MTHT was a very good inhibitor. 4-MTHT behaved better in 1 M HCl than in 0.5 M H 2 SO 4 and inhibition efficiencies up to 99% and 80% can be obtained in 1 M HCl and 0.5 M H 2 SO 4 , respectively. Activation energies ( E a ) in the presence and absence of 4-MTHT were obtained by measuring the temperature independence of the corrosion current. The potential of zero charge of mild steel was studied by ac impedance method, and the mechanism of adsorption has been discussed. The adsorption of 4-MTHT followed Langmuir's adsorption isotherm in both acids.
551 citations
TL;DR: In this paper, the adsorption and inhibition effect of Cefazolin on mild steel was studied by weight loss, EIS, potentiodynamic polarization and atomic force microscopy techniques.
Abstract: The adsorption and inhibition effect of Cefazolin on mild steel in 1.0 M HCl at 308–338 K was studied by weight loss, EIS, potentiodynamic polarization and atomic force microscopy techniques. The results showed that inhibition efficiency increased with inhibitor concentration. The adsorption of Cefazolin on mild steel surface obeys the Langmuir adsorption isotherm equation. Both thermodynamic (enthalpy of adsorption Δ H ads ∘ , entropy of adsorption Δ S ads ∘ and free energy of adsorption Δ G ads ∘ ) and kinetic parameters (activation energy Δ E a ∘ and pre-exponential factor A) were calculated and discussed. Polarization curves showed that Cefazolin acted as mixed-type inhibitor controls predominantly cathodic reaction.
436 citations
TL;DR: In this paper, the corrosion inhibition of mild steel in 10 mM HCl solution by four Schiff bases was investigated using weight loss and electrochemical measurements and quantum chemical calculations All compounds showed >90% inhibition efficiency at their optimum concentrations The activation energy of corrosion and other thermodynamic parameters were calculated to elaborate the mechanism of corrosion inhibition.
Abstract: The corrosion inhibition of mild steel in 10 M HCl solution by four Schiff bases was investigated using weight loss and electrochemical measurements and quantum chemical calculations All compounds showed >90% inhibition efficiency at their optimum concentrations The activation energy (Ea) of corrosion and other thermodynamic parameters were calculated to elaborate the mechanism of corrosion inhibition The adsorption of the inhibitors on the mild steel surface follows Langmuir isotherm model Polarization studies indicated that all studied inhibitors are mixed type The computed quantum chemical properties viz, electron affinity (EA) and molecular band gap (ΔEMBG) show good correlation with experimental inhibition efficiencies
389 citations
TL;DR: In this article, two diamine derivatives, namely 2-[{2-[bis-(2-hydroxyethyl)amino]ethyl}(2]-hydroxy methyl amino]propanol (DAME) and DAMP, were synthesized and their inhibitive action against the corrosion of mild steel in 1-M HCl solution were investigated at 308-K.
Abstract: New diamine derivatives, namely 2-[{2-[bis-(2-hydroxyethyl)amino]ethyl}(2-hydroxyethyl)amino]ethanol (DAME) and 2-[{2-[bis-(2-hydroxyethyl)amino]ethyl}(2-hydroxyethyl)amino]propanol (DAMP) were synthesised and their inhibitive action against the corrosion of mild steel in 1 M HCl solution were investigated at 308 K. The detailed study of DAME is given using gravimetric measurements and polarization curves method. Results show that DAME is a good inhibitor and inhibition efficiency reaches 91.7% at 10 −3 M. Tafel polarization study revealed that DAME acts as a mixed-type inhibitor. The inhibitor adsorption process in mild steel/DAME/hydrochloric acid system was studied at different temperatures (308–353 K) by means of weight loss measurements. The adsorption of DAME on steel surface obeyed Langmuir’s adsorption isotherm. The kinetic and thermodynamic parameters for mild steel corrosion and inhibitor adsorption, respectively, were determined and discussed. The comparative study of inhibitive performance of the two diamine derivatives revealed that DAME is more effective than DAMP. Quantitative Structure–Activity Relationship (QSAR) approach has been conducted in attempt to correlate the corrosion inhibition properties of these diamine derivatives with their calculated quantum chemical parameters.
301 citations
TL;DR: In this article, the effect of addition of 2[5-(2-pyridyl)-1,2,4-triazol-3-yl] phenol (PPT) on mild steel dissolution in 1 M hydrochloric acid is studied through electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation curves and gravimetric measurements.
Abstract: The effect of addition of 2[5-(2-pyridyl)-1,2,4-triazol-3-yl] phenol (PPT) on mild steel dissolution in 1 M hydrochloric acid is studied through electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation curves and gravimetric measurements. The obtained results showed that PPT revealed a good corrosion inhibition. Potentiodynamic polarisation studies indicate that PPT is a mixed-type inhibitor. The effect of temperature on the corrosion behaviour of mild steel in 1 M HCl with addition of 80 mg/l of PPT was studied in the temperature range from 25°C to 60°C. The associated activation corrosion and free adsorption energies have been determined. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) of the mild steel revealed that PPT is absorbed on the steel surface. PPT appears to function through the general adsorption mode following the Langmuir adsorption isotherm model.
236 citations
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TL;DR: In this paper, the authors investigated the kinetics of discharge of ZnII on a hanging Zn(Hg) drop by the galvanostatic method in perchlorate medium with out and with n-amyl alcohol.
Abstract: : The kinetics of discharge of Zn(II) on a hanging Zn(Hg) drop was studied by the galvanostatic method in perchlorate medium with-out and with n-amyl alcohol. The Frumkin correction for the double layer structure was verified in the absence of n-amyl alcohol for Mg(C104)2 and Ba(C104)2, but departure was considerable for NaC104 and A1(C104)3. This discrepancy is tentatively explained. An explanation is offered, and the significance of coverage, as computed from thermodynamic surface excesses, is discussed. The transfer coefficient was not affected by the presence of n-amyl alcohol. It is concluded that the plane of closest approach for zinc ion is not affected by the presence of n-amyl alcohol. (Author)
46 citations
TL;DR: In this article, the exchange current density values for the zinc amalgam electrode, Zn(Hg)/Zn 2+ in 5· 10 −2 N Na 2 SO 4 in both the presence and absence of surface active organic substances, n-valeric acid, diethyl ketone and n-amyl alcohol, were determined by the galvanostatic transient method.
Abstract: Summary The exchange current density values for the zinc amalgam electrode, Zn(Hg)/Zn 2+ in 5· 10 −2 N Na 2 SO 4 in both the presence and absence of surface active organic substances, n-valeric acid, diethyl ketone and n-amyl alcohol, were determined by the galvanostatic transient method. Similarly, the exchange current density values for the cadmium amalgam electrode in 5·10 −2 N Na 2 SO 4 were determined in both the absence and presence of n-amyl alcohol. The values were corrected for the changes in the Ψ 1 potential caused by the adsorption of the organic substance. The inhibition coefficient was calculated from the corrected exchange current density values for different concentrations of the organic substance, and the values compared with the corresponding adsorption isotherm.
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