Inhibitive action of the purine and adenine for copper corrosion in sulphate solutions

The influence of the concentration of the purine (PU) and adenine (AD) on the corrosion of copper in 0.5 M Na₂SO₄ solutions (pH 6.8) was studied. The investigations involved electrochemical polarization methods as well as electrochemical quartz crystal microbalance (EQCM) techniques. The inhibition efficiency increases with an increase in the concentration of PU and AD. Adherent layers of inhibitors were postulated to account for the protective effect. The adsorptions of inhibitors were found to occur on the surface of copper according to the Langmuir isotherm. The values of standard free energies of adsorption suggest the chemical adsorption of PU and AD on the copper surface.     

Corrosion inhibition of copper by purine or adenine in sulphate solutions

The influence of the concentration of purine (PU) or adenine (AD) on the spontaneous dissolution of copper in 0.5 M Na₂SO₄ solutions (pH 6.8 and 1.0) was studied. The investigations involved weight loss measurements, quartz crystal microbalance (QCM) techniques and scanning electron microscopy (SEM). The inhibition efficiency increases with an increase in the concentration of PU or AD. An adherent layer of inhibitors are postulated to account for the protective effect. The adsorption of both inhibitors was found to occur on the surface of copper according to the Langmuir isotherm. The values of standard free energies of adsorption suggest the chemical adsorption of PU and AD on copper surface.     

Novel benzimidazole derivatives as corrosion inhibitors of mild steel in the acidic media. Part I: Gravimetric,electrochemical, SEM and XPS studies

Three novel benzimidazole derivatives, 2-aminomethyl benzimidazole (ABI), bis (2-benzimidazolylmethyl) amine (BBIA) and tri (2-benzimidazolylmethyl) amine (TBIA), have been studied as inhibitors for mild steel in 1.0 M HCl. The three compounds prevent mild steel from corrosion by adsorption on the steel surface and forming insoluble complex with ferrous species. Inhibition efficiency increases with the increase in the number of benzimidazole segments in the molecules (TBIA > BBIA > ABI). Protection efficiency of the inhibitors depends on concentration of inhibitor, temperature and concentration of hydrochloric acid.     

Investigation of some Schiff base compounds containing disulfide bond as HCl corrosion inhibitors for mild steel

The inhibition performance of three Schiff bases containing disulfide bond as corrosion inhibitors for mild steel in 2.0 M HCl has been investigated by weight loss measurements, potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). Potentiodynamic polarization study showed that all the inhibitors are mixed type. The adsorption of inhibitors on mild steel surface was found to follow Langmuir adsorption isotherm and the adsorption isotherm parameters (K_ads, ΔG_ads) were determined. Quantum chemical calculations were further applied to reveal the adsorption structure and explain the experimental results. Some samples of mild steel were examined by SEM.     

Factors affecting the corrosion behaviour of aluminium in acid solutions. II. Inorganic additives as corrosion inhibitors for Al in HCl solutions

CrO₄²⁻, WO₄²⁻ and HPO₄²⁻ ions affect on the corrosion behaviour of Al in 2 M HCl. The inhibition efficiencies of the additives depend on their type and increase with increasing concentration. Oxide film destruction and/or repair follow a direct logarithmic law. The inhibitive action of these anions is discussed in terms of competitive adsorption with Cl⁻ ions on the electrode surface followed by a reduction mechanism to form metal oxides. The calculated values of ΔG°_ads of the inhibition process reveal a physical adsorption of the inhibitors. The inhibition efficiency is found to decrease in the order: CrO₄²⁻ > WO₄²⁻ > HPO₄²⁻.     

Adsorption and inhibition effect of Ascorbyl palmitate on corrosion of carbon steel in ethanol blended gasoline containing water as a contaminant

The adsorption and inhibition effect of Ascorbyl palmitate (AP) on carbon steel in ethanol blended gasoline containing water as a contaminant (GE10 + 1%water) was studied by weight loss and electrochemical impedance spectroscopic (EIS) techniques. The results showed that the addition of ethanol and water to gasoline increase the corrosion rate of carbon steel. AP inhibits the corrosion of carbon steel in (GE10 + 1% water) solution to a remarkable extent. The adsorption of AP on the carbon steel surface was found to obey the Langmuir adsorption isotherm model. The values of activation energy (E_a) and various thermodynamic parameters were calculated and discussed.     

Copper corrosion mitigation by binary inhibitor compositions of potassium sorbate and benzotriazole

This work presents the combined effect of two inhibitors, potassium sorbate (2,4-hexadienoic acid potassium salt) and 1,2,3-benzotriazole, on the corrosion behavior of copper in sulfate based solutions. Individual and combined characteristics of copper corrosion inhibition in sulfate solution in the presence of potassium sorbate (K-sorbate) and benzotriazole (BTAH) were studied with the use of electrochemical, microscopic and spectroscopic methods. Whereas, BTAH alone protects copper from corrosion attack in sulfate solutions only in a limited potential range below 0.4 V vs. saturated calomel electrode (SCE), the presence of K-sorbate combined with BTAH in such solutions enables the protection of the copper surface at potentials above 0.4 V_SCE. The mixture of both inhibitors provides supplementary and robust corrosion protection of Cu over a wide potential range.     

Innovative use of biologically produced ferric sulfate for machining of copper metal and study of specific metal removal rate and surface roughness during the process

The biologically produced ferric sulfate (in the form of bacterial culture supernatant) was used for machining of copper metal workpiece. A 27.04 mg/h cm² average specific metal removal rate was achieved during oxidation of copper workpiece. The leaching performance of culture supernatant was comparable to that of microbial cells indicating that an indirect non-contact leaching mechanism is predominant for metal solubilization. The surface of copper workpiece was analyzed by scanning electron microscopy before and after oxidation. The changes in surface appearance were found during oxidation of copper. Also the change in surface roughness was observed during machining process. The quality of the surface produced is a very important aspect of the performance of the manufacturing process. Therefore the present study characterizes an effect of various physicochemical parameters on specific metal removal rate and surface roughness. An increasing concentration of FeSO₄, shaking speed and volume of culture supernatant showed pronounced effect on metal removal and surface roughness. At the same time an application of varying temperatures showed little effect.     

Inhibition by Ginkgo leaves extract of the corrosion of steel in HCl and H2SO4 solutions

The inhibition effect of Ginkgo leaves extract (GLE) on the corrosion of cold rolled steel (CRS) in 1.0–5.0 M HCl and 0.5–2.5 M H₂SO₄ solutions was investigated for the first time by weight loss, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) methods. The results show that GLE is a good inhibitor, and exhibits more efficient in 1.0 M HCl than 0.5 M H₂SO₄. The adsorption of GLE on CRS surface obeys Langmuir adsorption isotherm. GLE acts as a mixed-type inhibitor in 1.0 M HCl, while a cathodic inhibitor in 0.5 M H₂SO₄.     

Synthesis and hydrogen storage of carbon nanofibers

Carbon nanofibers were synthesized by catalytic decomposition of methane using Ni–MgO catalyst and hydrogen adsorption experiments were carried out by a Sievert’s apparatus under 120 bar at 25 °C. Hydrogen adsorption capacity was elevated up to 1.4 wt.% after heat treatment at 1200 °C in N₂ atmosphere. CO and CO₂ were detected by gas chromatography (GC) during heat treatment which promoted active surface suitable for hydrogen adsorption of carbon nanofibers. High resolution transmission electron microscopy (HRTEM) and XRD analysis revealed that the structure of carbon nanofibers was durable after hydrogen uptake even at high pressures.     

A corrosion study of nanocrystalline copper thin films

Thin nanocrystalline, compact films, based on the copper–nitrogen system, up to 2.5 μm thickness and 3.5% nitrogen, were deposited by magnetron sputtering at different partial pressure ratios of N₂ and Ar, without formation of Cu_xN compounds, the nitrogen concentration influencing grain size (down to 30 nm) and film homogeneity. Electrochemical corrosion properties were investigated using polarization curves and electrochemical impedance spectroscopy in 0.5 M NaCl aqueous solution, and compared with pure bulk copper; morphology was examined by scanning electron microscopy. Significant variations in corrosion currents between samples were attributed to grain size and structural defects on the grain boundaries.     

Flexible polyurethane foams as templates for cellular glass–ceramics

In this work flexible polyurethane (PU) foams were obtained with varying air permeability, cell diameter and morphology. The addition of up to 1.5 g anti-foamer with a mixing time of 75 s resulted in larger cell diameters, higher air permeability and lower distorted area. PU foams obtained were used as templates to produce glass–ceramic (GC) foams by the replication method. Glass powder of the LZSA (Li₂O–ZrO₂–SiO₂–Al₂O₃) system was used to infiltrate the PU foams. The retention capacity of the ceramic suspension in PU foam is increased with a reduction of the cell diameter. In contrast, the infiltration capacity increases with raise of the cell diameter. The permeability reduction of GC foams with respect to PU foams varied from 3% to 25% when 2.7 and 0.8.0 mm cell diameters were used, respectively. The results of mechanical characterization were coherent with the morphological characteristics in both PU and GC foams.     

Electrochemical and quantum chemical studies of some azomethine compounds as corrosion inhibitors for mild steel in 1 M hydrochloric acid

The corrosion inhibition effect of new azomethine compounds: PhNNC (COCH₃)NC₆H₄Y {Y = OCH₃ (SB₁), CH₃ (SB₂), H (SB₃), Br (SB₄) and Y = Cl (SB₅)} on mild steel in 1 M HCl, was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemistry analysis. It has been found that the inhibition efficiency increased with increasing inhibitor concentration. The polarization curves showed that these Schiff bases function as mixed inhibitors. The adsorption of studied compounds on mild steel surface was found to follow the Langmuir isotherm. Molecular modeling was used to correlate corrosion inhibition properties and calculated quantum chemical parameters.     

Adsorption and corrosion inhibition of phytic acid calcium on the copper surface in 3 wt% NaCl solution

The adsorption and corrosion protection effect of phytic acid calcium (PAC) film on the copper surface in 3 wt% NaCl solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Raman spectroscopy. Polarization curves indicate that PAC is a mixed inhibitor, affecting both cathodic and anodic corrosion currents. The inhibition efficiency of PAC film reached 92.53% at an optimized condition. Adsorption of PAC molecules on the surface followed Langmuir adsorption isotherm and the standard Gibbs energy of −37.32 kJ mol⁻¹ indicated a chemisorptive way. Raman studies suggested that PAC molecule chemically anchored at the surface via PO groups.     

2-Butyne-1,4-diol as a novel corrosion inhibitor for API X65 steel pipeline in carbonate/bicarbonate solution

The inhibition effects of 2-butyne-1,4-diol on the corrosion susceptibility of grade API 5L X65 steel pipeline in 2 M Na₂CO₃/1 M NaHCO₃ solution were studied by electrochemical techniques and weight loss measurements. The results indicated that this inhibitor was a mixed-type inhibitor, with a maximum percentage inhibition efficiency of approximately 92% in the presence of 5 mM inhibitor. Atomic force microscopy revealed that a protective film was formed on the surface of the inhibited sample. The adsorption of the inhibitor was found to conform to the Langmuir isotherm with the standard adsorption free energy of ?21.08 kJ mol^?1.     

Titanium-supported Ce-, Zr-containing oxide coatings modified by platinum or nickel and copper oxides and their catalytic activity in CO oxidation

A combination of plasma electrolytic oxidation (PEO) and impregnation techniques followed by annealing in air has been used to obtain composites Pt/nZrO₂ + pTiO₂/Ti, Pt/nZrO₂ + pTiO₂ + zCeO_x/Ti, NiO + CuO/nZrO₂ + pTiO₂/Ti, NiO + CuO/nZrO₂ + pTiO₂ + zCeO_x/Ti with different zirconium and titanium contents and ZrO₂/TiO₂ phase ratio. The composites have been investigated by means of XRD, XPS and SEM/XSA methods. According to the XPS data, the platinum content on the coating surface is ~ 0.4 at.%, whereas the XSA measurements have shown that the nickel and copper contents in coatings attain 16 and 8 at.%, respectively, depending on the initial oxide coatings composition. Nickel and copper oxides form either extended islets or solid layers (“crusts”) on the coating surface. Both the composites promoted with platinum and those with the “crust” built from nickel and copper oxides are active in CO oxidation at the temperatures above 200 °C and 300 °C, respectively.     

Corrosion behaviour of niobium in phosphate buffered saline solutions with different concentrations of bovine serum albumin

The corrosion behaviour of Nb was studied in phosphate buffered saline (PBS) solutions at a presence of 0–6 g L⁻¹ bovine serum albumin (BSA). Addition of BSA to PBS solutions lowered the open circuit potential (OCP). OCP, polarization resistance and impedance increased over immersion time. The adsorption process of BSA on Nb surface was found to be faster than that of the PO₄³⁻. According to X-ray Photoelectron Spectroscopy (XPS) a competitive adsorption between PO₄³⁻ and BSA was in effect during the immersion process. Based on the analysis of effective capacitances, a surface distribution of time-constants was proposed.     

Schiff’s base of pyridyl substituted triazoles as new and effective corrosion inhibitors for mild steel in hydrochloric acid solution

Three Schiff’s bases namely (3-phenylallylidene) amino-5-(pyridine-4-yl)-4H-1,2,4-triazole-3-thiol (SB-1), 3-mercapto-5 (pyridine-4-yl)-4H-1,2,4-triazole-4-yl) imino) methyl) phenol (SB-2) and (4-nitrobenzylidene) amino)-5-(pyridine-4-yl)-4H-1,2,4-triazole-3-thiol (SB-3) were synthesized and investigated as corrosion inhibitors for mild steel (MS) in 1 M HCl. SB-1 exhibited best inhibition performance (96.6 η%) at 150 mg L⁻¹. The studied inhibitors follow Langmuir adsorption isotherm. Potentiodynamic polarization data suggests mixed-mode of corrosion inhibition. The effect of molecular structure on inhibition efficiency was investigated by theoretical calculations using density function theory (DFT) methods. Surface analysis supports the formation of a protective inhibitor film on the mild steel surface.     

2-Amino-5-(4-pyridinyl)-1,3,4-thiadiazole monolayers on copper surface: Observation of the relationship between its corrosion inhibition and adsorption structure

Corrosion inhibition behavior of 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole (4-APTD) monolayers on copper surface were investigated by electrochemical impedance spectroscopy (EIS), electrochemical polarization measurement and surface-enhanced Raman scattering (SERS) experiment. The EIS mechanism of the copper surface with 4-APTD monolayers fitted to the mode of R(Q(R(QR))). The electrochemical polarization measurements indicated high inhibition efficiency of about 90.4%. SERS results suggested that 4-APTD molecules anchored at copper surface in a tilted orientation directly via N³ and N¹² atoms. The transition adsorption states of 4-APTD on the copper surface were observed as the potential applied from 0 to −1.6 V vs. SCE.     

Nonenzymatic glucose sensor based on gold–copper alloy nanoparticles on defect sites of carbon nanotubes by spontaneous reduction

Gold (Au) and copper (Cu) alloy catalysts were deposited on the defect sites of carbon nanotubes by spontaneous reduction among AuCl₄^?, Cu²⁺ and oxygen-containing functional groups. Compared with AuCu alloy catalysts prepared by adsorption methods and electrochemical deposition methods, AuCu alloy catalysts show excellent catalytic ability to glucose by spontaneous reduction. The linear range of nonenzymatic sensors that were prepared by spontaneous reduction for glucose detection is 0.08–9.26 mM, and detection limit is 4 μM. In addition, there are high sensitivity (22 μA mM^?1), reproducibility (96%) and stability (95% after 60 days). Selectivity of this nonenzymatic sensor for ascorbic, uric acid and acetaminophen was also obtained.