Experimental and Theoretical Evaluation of Rutin as Eco-Friendly Corrosion Inhibitor for Aluminum 6063 Alloy in Acidic Medium

The corrosion inhibition characteristics of rutin a natural flavonoid glycoside has been studied as an eco-friendly green inhibitor for corrosion control of aluminum alloy AA6063 in 0.5 M HCl medium at a temperature range of 30–60 °C by weight loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques. The inhibition efficiency increased with the increase in concentration of the inhibitor and also with increase in temperature. The surface morphologies of the polished, corroded and inhibited surfaces were scanned using the scanning electron microscope images. The activation parameters like energy of activation, enthalpy of activation and entropy of activation were calculated and analyzed. Thermodynamic parameters for the adsorption of the inhibitor on the metal alloy surface were calculated and analyzed. The inhibitor acted as a mixed inhibitor. The mechanism of adsorption deduced from the variation of inhibition efficiency with temperature as well as kinetic and activation parameters suggests significant chemisorption of the inhibitor on the metal surface. The mechanism of inhibition can partly be attributed to the possible coordination of rutin to form stable aluminum–rutin complex. The maximum inhibition efficiency was found to be 95.1 and 94.45% by PDP and EIS studies, respectively, at 60 °C. Density functional theory calculations under the level B3LYP/6-311G(d) is utilized for the calculation of quantum chemical parameters.     

Electrochemical properties and dissolution of URu<Subscript>3</Subscript> in nitric acid solutions

The electrochemical properties of URu₃ intermetallic compound (IMC) in 0.5–8 M HNO₃ solutions were studied by linear voltammetry and galvanostatic electrolysis. In 0.5–2 M HNO₃, URu₃ occurs in the passive state at potentials lower than +1.3 V (here and hereinafter, vs. SHE), and in 4–8 M HNO₃, an anodic oxidation peak is observed at potentials from +1.0 to +1.2 V. This process, however, leads to IMC passivation and not to its dissolution. At potentials higher than +1.4 V, URu₃ passes into the transpassive state and starts to actively dissolve. The principal possibility of electrochemical dissolution of IMC at potentials exceeding the transpassivation potential was demonstrated by galvanostatic electrolysis. The rate of uranium leaching during electrolysis depends to a greater extent on the current density than on the HNO₃ concentration and reaches 35 mg cm^–2 h^–1 in 6 M HNO₃ at a current density of 182 mA cm^–2.     

Electrochemical,surface analytical and quantum chemical studies on Schiff bases of 4-amino-4H-1, 2, 4-triazole-3,5-dimethanol (ATD) in corrosion protection of aluminium in 1N HNO<Subscript>3</Subscript>

The present study describes the inhibition of aluminium in 1N HNO₃ with different concentrations of 1,2,4-triazole precursors ATD, BATD and DBATD using gravimetric method, potentiodynamic polarization studies (Tafel), electrochemical impedance spectroscopy (EIS), adsorption studies, surface morphological studies and quantum chemical calculations at 298 K. Polarization studies clearly showed that ATD, BATD and DBATD act as mixed type inhibitors. As the electron density around the inhibitor molecule increases due to substitution, the inhibition efficiency also increases correspondingly. Quantum chemical approach was used to calculate some electronic properties of the molecule to ascertain the correlation between inhibitive effect and molecular structure of the inhibitor. The corrosion inhibition efficiencies of these molecules and the global chemical reactivity relate to some parameters, such as E _HOMO , E _LUMO , gap energy (ΔE), electronegativity (χ), global hardness (η) and the fraction of electrons transferred from the inhibitor molecule to the metallic atom (DN\Delta \emph{N}). In addition, the local reactivity has been analysed through the Fukui function and condensed softness indices. Both the experimental and theoretical studies agree well in this regard and confirm that DBATD is a better inhibitor than BATD and ATD. The adsorption behaviours of molecules on the copper surface have been studied using molecular dynamics method and density functional theory. The order of inhibitory action is DBATD > BATD > ATD.     

Inhibition of corrosion of mild steel in acid media by N′-benzylidene-3-(quinolin-4-ylthio)propanohydrazide

In the present investigation a new corrosion inhibitor, N′-(3,4-dihydroxybenzylidene)-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide(DHBTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in HCl (1 M, 2 M) and H₂SO₄ (0·5 M, 1 M) solutions using weight-loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The corrosion inhibition efficiency measured by all the above three techniques were in good agreement with each other. The results showed that DHBTPH is a very good inhibitor for mild steel in acidic media. The inhibition efficiency in different acid media was found to be in the decreasing order 0·5 M H₂SO₄ > 1 M HCl > 1 M H₂SO₄ > 2 M HCl. The inhibition efficiency increases with increasing inhibitor concentration and with increasing temperature. It acts as an anodic inhibitor. Thermodynamic and activation parameters are discussed. Adsorption of DHBTPH was found to follow the Langmuir’s adsorption isotherm. Chemisorption mechanism is proposed. The mild steel samples were also analysed by scanning electron microscopy (SEM).     

The inhibition of mild steel corrosion in 1 M hydrochloric acid solutions by triazole derivative

The title compound 1-(4,5-dihydro-3-phenylpyridine-1-yl)-2-(1H-1,2,4-triazole-1-yl)ethyl ketone (DTE) was synthesized and its inhibiting action on the corrosion of mild steel in 1 M hydrochloric acid solutions was investigated by means of weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electronic microscope (SEM). Results obtained revealed that DTE performed excellently as a corrosion inhibitor for mild steel in 1 M hydrochloric acid media and its efficiency attains more than 90.9% at 1.0 × 10^− 3 M at 298 K. Polarization curves indicated that the inhibitor behave mainly as mixed-type inhibitor. EIS showed that the charge transfer controls the corrosion process in the uninhibited and inhibited solutions. Adsorption of the inhibitor on the mild steel surface followed Langmuir adsorption isotherm. And the values of the free energy of adsorption ΔG_ads indicated that the adsorption of DTE molecule was a spontaneous process and was typical of chemisorption.     

Kinetics of Np(V) transformation in concentrated HNO<Subscript>3</Subscript> solutions containing potassium phosphotungstate K<Subscript>10</Subscript>P<Subscript>2</Subscript>W<Subscript>17</Subscript>O<Subscript>61</Subscript>

The behavior of Np(V) in concentrated HNO₃ solutions containing potassium phosphotungstate K₁₀P₂W₁₇O₆₁ (KPW) at various concentrations of HNO₃ (1.0–3.0 M) and KPW [(1–5) × 10^?3 M] was studied. Under the examined experimental conditions, the final products of Np(V) transformation are Np(IV) and Np(VI). The reaction follows a first-order rate equation with respect to the Np(V) concentration.     

Electrochemical properties and dissolution of UPd<Subscript>3</Subscript> in nitric acid solutions

Electrochemical properties of the intermetallic compound UPd₃ in 0.5–8 M HNO₃ solutions were studied by linear voltammetry. In 0.5–2 M HNO₃ solutions, the UPd₃ surface is in the passive state. At HNO₃ concentrations exceeding 4 M, the alloy passivation was not observed. The previously unknown electrochemical characteristics of UPd₃ in nitric acid solutions were obtained using the Tafel equation. The values of Е(i = 0) and v_corr increased from 39 mV and 38 μg cm^–2 h^–1 in 0.5 M HNO₃ to 821 mV and 11 mg cm^–2 h^–1 in 8 M HNO₃, respectively. Dissolution experiments have shown that UPd₃ can dissolve in HNO₃ solutions of concentration exceeding 4 M at room temperature. In 8 M HNO₃, the dissolution rate can reach 17 mg cm^–2 h^–1 at 25°С, with the dissolution being virtually equimolar and accelerating with time.     

Effect of NaBr on the corrosion of cold rolled steel in 1.0 M phosphoric acid

The inhibition of NaBr on the corrosion of cold rolled steel in 1.0 M phosphoric acid was studied by using weight loss method and polarization method. It was found that the adsorption of bromide ion can prevent steel from corrosion and the adsorption follows the Langmuir adsorption isotherm. Polarization studies showed that NaBr is a mixed-type inhibitor for steel corrosion in 1.0 M phosphoric acid. Thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy were obtained from the experimental data of temperature studies for the inhibition process at four temperatures ranging from 30 to 45°C. The kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, and the effects of the apparent activation energy and pre-exponential factor on the corrosion rate of cold rolled steel were discussed. The inhibitive action was satisfactorily explained by using thermodynamic and kinetic models. The results obtained from polarization experiment were in good agreement with those obtained from weight loss measurement.     

Electrochemical properties and solubility of URh<Subscript>3</Subscript> in nitric acid solutions

Electrochemical properties of the intermetallic compound URh₃ in 0.5–8 M HNO₃ solutions were studied by linear voltammetry. The electrochemical characteristics of URh₃ in nitric acid solution were determined for the first time using the Tafel equation. URh₃ is highly resistant to both chemical and anodic dissolution, which is due to formation of passive films on the electrode surface. All the anodic oxidation processes observed on the electrode led to secondary passivation of the alloy and not to its dissolution. The conclusions based on the electrochemical data were confirmed by experiments in 8 M HNO₃.     

Effect of menthol coated craft paper on corrosion of copper in HCl environment

Natural menthol was coated on craft paper by impregnation and studied as volatile corrosion inhibitor for copper in hydrochloric acid environment. The effect of menthol on copper corrosion was studied by gravimetric and electrochemical methods such as potentiodynamic polarization and electrochemical impedance measurements. The results indicate that menthol adsorbs on the metal surface, which protects copper against further corrosion. The adsorption behaviour of menthol on copper surface was found to obey Temkin’s adsorption isotherm.     

Electrochemical impedance study on the corrosion of Al-Pure in hydrochloric acid solution using Schiff bases

The inhibition effect of newly synthesized Schiff bases N-benzylidene benzylamine (A) and benzenemethanamine-α-methyl-N-(phenylmethylene) (B) on the corrosion behaviour of Al-Pure in 1·0 M HCl was studied using galvanostatic polarization and electrochemical impedance spectroscopy (EIS) and adsorption studies. The effects of inhibitor concentration, temperature and surface coverage are investigated. The effect of inhibitor concentration and other parameters are evaluated for different inhibitor concentrations and the probable mechanism was also proposed. The results show that (A) and (B) possess excellent inhibiting effect for the corrosion of Al-Pure and the inhibitors act as mixed type inhibitors. The inhibitors do not affect the mechanism of the electrode processes and inhibit corrosion by blocking the reaction sites. The high inhibition efficiency of (A) and (B) were due to the adsorption of inhibitor molecules on the metal surface. The decrease of surface area available for electrode reactions to take place is due to the formation of a protective film. Activation energy and free energy of adsorption have been calculated.     

Electrochemical and quantum chemical study of 4-[(E)-[(2,4-dihydroxy phenyl) methylidine] amino]-6-methyl-3-sulphanylidine-2,3,4,5-tetra hydro-1,2,4-triazin-5-one [DMSTT]

The inhibition of mild steel in aerated 1 M hydrochloric acid solution was studied using conventional weight loss method, potentiodynamic polarization studies (Tafel), linear polarization studies (LPR), electrochemical impedance spectroscopy (EIS) and quantum chemical calculation in the presence and absence of different concentrations of DMSTT. The inhibition efficiency increased markedly with increase in the additive concentrations, but slightly decreased with increasing temperature. The presence of DMSTT decreases the double layer capacitance and increases the charge-transfer resistance. The value of activation energy (E_a) for mild steel corrosion and thermodynamic parameters such as adsorption equilibrium constant (K_ads), free energy of adsorption (ΔG_ads) values were calculated and discussed. The inhibitor molecule first adsorbed on mild steel surface according to Langmuir adsorption isotherm.     

Electrochemical performance of steel in cement extract and bulk matrix properties of cement paste in the presence of Pluronic 123 micelles

The influence of Pluronic P123 (PEO₂₀-PPO₇₀-PEO₂₀) non-stabilized micelles (of 10 nm size) on the corrosion behavior of low-carbon steel in cement extract was studied, using electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization (PDP). Mercury intrusion porosimetry (MIP) was employed to derive the impact of admixed P123 micelles on porosity and pore-size distribution of cement paste. As far as steel corrosion resistance is concerned, a positive effect was observed, initially denoted to the presence of the polymer itself, rather than the presence of micelles. Further, the P123 micelles were found to result in increased corrosion resistance in the presence of 1 % and 3.5 % NaCl in the alkaline environment of cement extract. There was no significant influence on porosity and pore size distribution of the admixed in cement paste P123 micelles. The observed phenomena are related to self-assembly of the micelles only within higher ionic strength and the presence of chloride, in which case the critical micelle concentration is reduced. At micelles concentration of 0.024 g/l for the chloride-free cement extract (and the solid cement paste specimens, respectively), the medium actually contain unimers that have minimal impact on electrochemical performance and/or microstructural properties. In contrast, with increased ionic strength of the medium (1?3.5 % NaCl and altered ion concentrations resulting from the anodic/cathodic reactions within steel corrosion), the positive effect of 0.024 g/l micelles (and higher of 0.072 g/l) is more pronounced, i.e., increased corrosion resistance and anodic control with external polarization was observed.     

Substrate dependent morphological and electrochemical properties of V<Subscript>2</Subscript>O<Subscript>5</Subscript> thin films prepared by spray pyrolysis

A scheme of substrate dependent self-organization of vanadium oxide has been used to create unique supercapacitor electrodes. In present work, thin films of V₂O₅ were prepared on different substrates by using well known spray pyrolysis technique.The sample depositions were carried out at 673 K, by spraying 0.05 M, 40 ml solution of ammonium metavanadate at the spray rate 10 ml/min. V₂O₅ thin films grown on aluminum (Al), copper (Cu) and stainless steel (SS) substrates shows porous valley and mountains, rough and dense morphology with overgrown agglomeration of nano grains. In electrochemical characterizations, by using standard electrode configurations, specific capacitance values were evaluated from cyclic voltammetry in 1 M KCl, these are 18.43, 1500.0, 439.60 and 250.58 F/g at 5 mV/s for the electrodes deposited on Al, Cu, SS substrates and two electrode cell respectively. Charge discharge behavior of the SS electrode and two electrode cell was observed using chronopotentiometry. This exhibits specific energy, specific power, and coulombic efficiency (η) 84.91 Wh/kg, 120.00 kW/kg and 89.51 % for SS electrode and 19.92 Wh/kg, 65.00 kW/kg and 99.90 % for two electrode cell respectively. Impedance study was carried out in the frequency range 1 mHz–1 MHz depicts less internal resistance of SS electrode ~2.69 Ω and two electrode cell ~3.04 Ω.     

Adsorption and corrosion inhibition effect of 2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol Schiff base on mild steel

In this study, the inhibition effect of 2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol Schiff base (MTMP) on mild steel corrosion in 0.5 M HCl solution was studied. For this aim, electrochemical techniques such as potentiodynamic polarization curves, weight loss (WL), electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) were used. It was shown that, the MTMP Schiff base has remarkable inhibition efficiency on the corrosion of mild steel in 0.5 M HCl solution. Polarization measurements indicated that, the studied inhibitor acts as mixed type corrosion inhibitor with predominantly control of cathodic reaction. The inhibition efficiency depends on the concentration of inhibitor and reaches 97% at 1.0 mM MTMP. The remarkable inhibition efficiency of MTMP was discussed in terms of blocking of electrode surface by adsorption of inhibitor molecules through active centers. The adsorption of MTMP molecules on the mild steel surface obeys Langmuir adsorption isotherm.     

Cathodic electrosynthesis of CuFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/CuO composite nanostructures for high performance supercapacitor applications

In this work, CuFe₂O₄/CuO nanocomposites have been synthesized by galvanostatic cathodic electrodeposition. The obtained nanocomposites were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier Transform Infrared, and Brunauer–Emmett–Teller surface area analysis. The electrochemical properties of CuFe₂O₄/CuO nanocomposites were evaluated by cyclic voltammetry, galvanostatic charge–discharge cycling, and electrochemical impedance spectroscopy in 1.0 M KOH. The CuFe₂O₄/CuO nanocomposites have shown the high specific capacitance of 322.49 F g^?1 at the scan rate of 1 mV s^?1. After 5000 cycles, 92% of this specific capacitance was retained. Although the prepared nanocomposite has shown a mediocre specific capacitance compared to other metal oxide-based materials, the low cost of the starting materials and the ease of preparation make this nanocomposite a good candidate for supercapacitor applications.     

Bis-triazole as a new corrosion inhibitor for copper in sulfate solution. A model for synergistic inhibition action

Bis-[4H-5 hydroxy-1, 2, 4-triazol-3-yl] methane BHTAM was tested as a promising new inhibitor for copper corrosion in 0.5 M Na₂SO₄ solutions using open – circuit potentials and galvanostatic polarization techniques. The results show that, BHTAM is an efficient inhibitor for copper corrosion in neutral medium. The anodic polarization is strongly affected by the presence of BHTAM compound as well as the cathodic polarization but to a lesser extent. The surface condition plays a significant role in the protection of copper. The pre-formed surface cuprous oxide films facilitate inhibitor adsorption as well as precipitation of insoluble [Cu (I) – BHTAM] complex.     

桂花果提取液在1 mol/L盐酸介质中对A3钢的缓蚀性能

为了开发A3钢盐酸清洗中的天然绿色缓蚀剂,通过索式提取法从桂花果中提取植物缓蚀剂,采用失重法、极化曲线和电化学阻抗谱(EIS)研究了不同浓度桂花果提取液在1 mol/L盐酸介质中对A3钢的缓蚀性能,并探讨了缓蚀机理。结果表明:以95%的乙醇为溶剂索式提取的桂花果提取液在1 mol/L盐酸介质中对A3钢具有良好的缓蚀性能,缓蚀效率随其浓度的增加而增大,当其浓度达到25 g/L时,缓蚀效率可达93%以上;桂花果提取液为混合型缓蚀剂,缓蚀机理为"几何覆盖效应",其有效缓蚀成分在A3钢表面的吸附符合Langmuir等温式,吸附平衡常数为1.89 L/g。     

Electrochemical characteristics of calcium-phosphatized AZ31 magnesium alloy in 0.9 % NaCl solution

Magnesium alloys suffer from their high reactivity in common environments. Protective layers are widely created on the surface of magnesium alloys to improve their corrosion resistance. This article evaluates the influence of a calcium-phosphate layer on the electrochemical characteristics of AZ31 magnesium alloy in 0.9 % NaCl solution. The calcium phosphate (CaP) layer was electrochemically deposited in a solution containing 0.1 M Ca(NO₃)₂, 0.06 M NH₄H₂PO₄ and 10 ml l^?1 of H₂O₂. The formed surface layer was composed mainly of brushite [(dicalcium phosphate dihidrate (DCPD)] as proved by energy-dispersive X-ray analysis. The surface morphology was observed by scanning electron microscopy. Immersion test was performed in order to observe degradation of the calcium phosphatized surfaces. The influence of the phosphate layer on the electrochemical characteristics of AZ31, in 0.9 % NaCl solution, was evaluated by potentiodynamic measurements and electrochemical impedance spectroscopy. The obtained results were analysed by the Tafel-extrapolation method and equivalent circuits method. The results showed that the polarization resistance of the DCPD-coated surface is about 25 times higher than that of non-coated surface. The CaP electro-deposition process increased the activation energy of corrosion process.     

Oxidation behavior and electrochemical corrosion performance of Ti<Subscript>3</Subscript>Al alloy with TiAl coating

Magnetron-sputter deposition was used to produce a Ti–48Al–8Cr–2Ag (at. %) coating on a Ti–24Al– 17Nb–0.5Mo (at. %) alloy substrate. Oxidation behavior was studied in air at 900–1000°C. The results indicated that the oxidation rate of sputtered Ti–48Al–8Cr–2Ag nanocrystalline coating was lower than that of the Ti₃Al alloy at 900°C. The former formed a scale of merely Al₂O₃, and the latter formed a scale of TiO₂. However, the Ti–48Al–8Cr–2Ag nanocrystalline coating showed a little bit higher oxidation rate than Ti₃Al alloy at 1000°C because the outer TiO₂ scale formed and columnar boundaries of the coating gave a larger actual oxidation area than the original alloy. The electrochemical corrosion behavior was investigated in a 3.5% NaCl solution at room temperature. The coating showed excellent electrochemical corrosion resistance in 3.5% NaCl solution because it exhibited stable passive polarization behavior without any overpassivation phenomena.