Copper In Alkaline Solutions Research Articles

Experimental and Computational Investigation of Salicylhydroxamic Acid as a Corrosion Inhibitor for Copper in Alkaline Solutions

Inhibitors, as indispensable components in chemical mechanical polishing (CMP) slurries, have a significant impact on inhibiting copper (Cu) corrosion and enhancing post-polishing surface quality. However, one of the major challenges in CMP lies in unraveling the microscopic corrosion inhibition mechanism of Cu. This work focuses on investigating the impact of an inhibitor, salicylhydroxamic acid (SHA), on the static etching rate (SER), electrochemical parameters, and surface morphology of Cu. The experimental findings demonstrate that SHA significantly decreases the SER and corrosion current density of Cu, while notably improving the Cu surface quality. The corrosion inhibition mechanisms of SHA on Cu are revealed through adsorption isotherm models, contact angle analysis, electrochemical impedance spectroscopy, and computational chemistry method. The benzene ring, oxime group, and O1 atom of SHA exhibit significant chemical reactivity, facilitating the preferential adsorption of SHA on Cu in a parallel orientation, thereby forming a hydrophobic protective film on the Cu surface. This process hinders the interaction between corrosive solutions and Cu, therefore SHA exhibits excellent corrosion inhibition performance on Cu. These findings hold great importance in gaining a deeper comprehension of the corrosion inhibition process of Cu, and provide guidance for designing more efficient inhibitors.

Aminophosphonate CuO nanocomposites for uranium(VI) removal: Sorption performance and mechanistic study

Two aminophosphonate matrices (mono-aminophopshonate, MAP, and bi-aminophosphonate, BAP) are synthesized, varying the molar proportions of three precursors (thiocarbazide, p-phthalaldehyde, and triphenylphosphite). Nano-composites (CuO-MAP and CuO-BAP) are successfully elaborated by impregnation of the matrices with copper sulfate solution before processing to in situ precipitation of copper in alkaline solution (simultaneous partial Cu reduction). The sorbents are characterized using: TEM, XRD, elemental analysis, SEM-EDX, BET, titration (pHPZC), XPS and FTIR analyses. Uranium sorption properties are compared for the different sorbents through the study of pH effect (optimum close to 4.5), the uptake kinetics (equilibrium reached in 60 min) and sorption isotherms. Uptake kinetics are finely fitted by the pseudo-second order rate equation (and the resistance to intraparticle diffusion). The sorption isotherms are modeled by the Langmuir equation with maximum sorption capacity (mmol U g−1) decreasing according to CuO-BAP(1.15) ≫ CuO-MAP(0.80) > BAP(0.74) ≫ MAP(0.50). The enhanced textural properties and the increase in the density of sorption sites (probably completed by a better steric arrangement for improved reactivity) may explain this ranking. The sorption is endothermic: sorption capacity and affinity coefficient increase with temperature. Uranium is readily desorbed from loaded-sorbents (efficiency > 98 %) using either HCl (0.2 M) solution or acidified urea (0.25 M) solution (pH 2.5) for aminophosphonate matrices and nano-composites, respectively. The type of sorbent does not affect the stability at recycling: at the sixth cycle, the loss in sorption and desorption performances varies by 6.2–7 % and 4.2–4.9 %, respectively. CuO-BAP sorbent shows high potential for uranium recovery from complex acid ore leachate. The broad spectrum of bound metals does not allow producing a pure yellow cake after ammonia precipitation of eluate (containing up to 15–22 % impurities).

Efficacious Alkaline Copper Corrosion Inhibition by a Mixed Ligand Copper(II) Complex of 2,2′‐Bipyridine and Glycine: Electrochemical and Theoretical Studies

AbstractA mixed ligand copper(II) complex, namely, [Cu(BPy)(Gly)Cl]⋅2H2O (CuC) (BPy=2,2′‐bipyridine and Gly=glycine), was synthesized and characterized. The synthesized CuC complex was tested as inhibitor to effectively mitigate the corrosion of copper in alkaline solutions using the linear sweep voltammetry (LSV) and linear polarization resistance (LPR) techniques. For the sake of comparison, such two D.C. electrochemical techniques were also applied to the Cu/OH− interface in the presence of the two studied free ligands, namely, BPy and Gly. The results showed that the three studied compounds acted as mixed‐type inhibitors, with CuC being the most efficacious one. The adsorption of the inhibitor is confirmed from X‐ray photoelectron spectroscopy (XPS) profiles by the appearance of organic chlorine as well as pyridine and amine nitrogen bonds. Based on XPS data, it was presumed that the corrosion inhibitor stimulates the formation of Cu2CO3(OH)2 species at the electrode surface since, in the case of a corroded reference sample (in absence of inhibitors), its proportion is trivial. The reactivity of the isolated inhibitors was analyzed by computing several quantum chemical parameters based on the density functional theory (DFT). A good correlation was found between these parameters and the anticorrosive performance. Additionally, Monte Carlo simulation studies were applied to find the best configurational space of ligands and their complex on the Cu(111) surface.

Electrochemical corrosion behavior and surface passivation of bulk nanocrystalline copper in alkaline solution

PurposeThis paper aims to focus on an assessment of the electrochemical corrosion performance of bulk NC copper in a variety of corrosion environments.Design/methodology/approachThe electrochemical corrosion behavior of bulk nanocrystalline (NC) copper prepared by inert gas condensation andin situwarm compress technique was studied by using potentiodynamic polarization and electrochemical impedance spectroscopy tests in de-aerated 0.1 M NaOH solution.FindingsNC copper exhibited a typical active-passive-transpassive behavior with the formation of duplex passive films, which was qualitatively similar to coarse-grain (CG) copper. Although a compact passive film formed on NC copper surface, the corrosion resistance of NC copper was lower in comparison with CG copper. The increase in corrosion rate for NC copper was mainly attributed to the high activity of surface atoms and intergranular atoms. These atoms led to an enhancement of passive ability and an increase of dissolution rate of passive film in oxygen-deficiency solution. For NC copper, the corrosion resistance decreased as grain size increased in NC range.Originality/valueThe difference in corrosion resistance between bulk NC copper and its CG counterpart is dependent upon the corrosion solution. In a previous work, the potentiodynamic polarization tests revealed that NC copper bulks (grain size 48, 68, 92 nm) had identical corrosion resistance to CG copper bulk in naturally aerated 0.1 M NaOH solution. The results might be related to the dissolved oxygen in the medium.

Fabrication of CuO/Cu/TiO2 nanotube arrays modified electrode for detection of formaldehyde

A CuO/Cu/TiO2 nanotube arrays (TNAs) modified electrode was fabricated by electrochemical method. Cu first deposited on TNAs electrode by a galvanostatic pulse method and CuO was prepared by in-situ oxidation copper in alkaline solution through cyclic voltammetry (CV). The effect of the cycle number of cyclic voltammograms and different substrate on the sensing performance were investigated. It was found that the optimal cycle number of CV is 100. The optimal CuO/Cu/TNAs electrode presents high sensitivity (814 μA mM−1cm−2) and wide linear range, with formaldehyde concentration from 65.0 μM to 7.80 mM, a detection limit of 25.0 μM (S/N = 3) and good repeatability, allowing prompt quantitative analysis of formaldehyde in alkaline solutions. Furthermore, compared to the glass carbon electrode (GCE) modified by a layer of CuO nanopaticles growing on the surface of Cu for the oxidation of formaldehyde, the CuO/Cu/TNAs electrode presents higher anodic oxidation current density and excellent cycling stability, showing that the CuO/Cu/TNAs electrode is more electro-active for oxidation of formaldehyde than the CuO/Cu/GCE. The prominent and stable electrocatalytic activity toward formaldehyde result from the synergistic effect between CuO/Cu and TNAs. In addition, the surface CuO nanoparticles on the CuO/Cu/TNAs electrode are more likely to form the highly active CuOOH species during oxidation process, which is the key to enhance the catalytic efficiency of CuO/Cu/TNAs electrodes.

The multiple roles of an organic corrosion inhibitor on copper investigated by a combination of electrochemistry-coupled optical in situ spectroscopies

The interaction of the organic corrosion inhibitor 2-mercaptobenzothiazole (MBT) with copper in alkaline solution was investigated by in situ infrared (IR) and Raman spectroscopy, and in situ spectroscopic ellipsometry, coupled to cyclic voltammetry (CV). At negative potentials, MBT monolayers relax on a minute time scale through MBT reorientation, leading to MBT-copper binding via S and N-atoms. After copper dissolution becomes thermodynamically feasible, including at open circuit, formation of a multilayer CuMBT complex sets in, in which thiol dominates over thione. Multilayer films effectively inhibit oxide formation. Instead, MBT oxidatively dimerises to 2,2′-dibenzothiazole disulfide (DBTA), which remains protective.

Spontaneous growth of CuO nanoflakes and microflowers on copper in alkaline solutions

Abstract CuO with different nano-architectures was synthesized by spontaneous corrosion of copper in alkaline aqueous solutions without any additives. CuO nanoflakes were obtained by simply immersing a copper foil in NaOH solution, while flower-like architectures constructed with nanopetals were produced in Na 2 CO 3 solution, indicating the pH value and the anions have a significant impact on the morphology and structure of CuO. The growth rate slowed down with the decrease of the alkalinity of the solution. In a more concentrated NaOH solution (1 M), polyhedron-like Cu 2 O was observed at the early stage before transforming into CuO nanoflakes. Based on these findings, massive production of nano-structured CuO powders was successfully realized by using copper powder as the precursor. The growing mechanism of flower-like CuO could be explained by the oriented attachment. The extensive sources of feedstock, the simple synthetic method and the uniform architecture of the products enable CuO to be utilized in a large scale.

Electrochemical Study of Bulk and Monolayer Copper in Alkaline Solution

The formation of copper oxides and hydroxides from metallic copper and underpotentially deposited copper atoms on platinum nanoparticles, when it is subjected to a potential scan between the hydrogen evolution potential and the oxygen evolution potential in alkaline solution as a function of scan rate and the pH of the solution has been investigated. Cyclic voltammetry of bulk copper electrodes in alkaline solution reveal that oxidation proceeds in steps leading to formation of Cu2O, Cu(OH)2 and CuO on the surface as well as some soluble oxides which corroborates well with X-ray photoelectron spectroscopy (XPS) analysis. Furthermore, interesting needle like formations on copper surface was observed in a scanning electron microscope (SEM), which can explain the unusual relation between the peak current and scan rate. On the other hand, the oxidation of copper monolayer on platinum nanoparticles leads primarily to formation of Cu2O and shows the effect of nobility imparted by the underlying platinum in terms of increased potential.

Semiconducting behavior of pure copper in alkaline solutions

The corrosion resistance of passive film is correlated with its semiconducting properties, which can be measured by the Mott–Schottky analysis in high frequency domain. In this study, the semiconducting behavior of passive films formed on pure copper in aqueous NaOH solutions was investigated using Mott–Schottky analysis. The polarization curves suggested that pure copper shows comparable passive behavior in NaOH solutions with different concentrations. Also, the potentiodynamic polarization curves showed corrosion current densities reduction with decrease in concentration of NaOH solutions. In Mott–Schottky analysis, no evidence of n-type semiconducting behavior was found, indicating that oxygen vacancies and copper interstitials do not have a significant population density in the passive film. Also, this analysis indicated that with the decrease of NaOH concentration in the solution, the acceptor density of passive films increases.

Copper corrosion inhibition by combined effect of inhibitor and passive film in alkaline solution

The work presents the combined effect of methionine molecules and cuprous oxide passive film on the corrosion inhibition of copper in 1 M NaOH solution by using potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy/energy dispersive X-ray analysis and theoretical calculations. The results reveal that methionine is an effective inhibitor for copper in 1 M NaOH solution and its inhibition efficiency is increased by increasing its concentration. Also, the electrochemical results showed that methionine mainly suppresses the cathodic process as a cathodic-typed inhibitor by adsorption, and the adsorption of methionine can occur on the passive film surface (cuprous oxide) of copper. The adsorbed film of inhibitors combines with the cuprous oxide passive film, and provides a double-layer protection for copper in alkaline solution. Quantum chemical calculation was applied to investigate the inhibition mechanism of methionine, and molecular dynamics simulation was further performed to illustrate the double-layer protection system for copper in alkaline solution.

Electrochemical investigation of cold worked copper in alkaline solution with the presence of potassium ethyl xanthate

This paper presents the investigation results of the electrochemical behavior of copper in 1 M Na2CO3 solution in the presence of potassium ethyl xanthate (KEtX) with different concentrations. Tests were conducted on copper samples obtained without deformation and with deformation of 83, 91 and 99 %. Samples were obtained by cold drawing of wire, which was previously obtained by dip-forming procedure. Corrosion behavior of cold deformed copper wire is characterized by its open circuit potential and behavior during anodic polarization. Experiments were carried out in aqueous solution 1 M Na2CO3 with added various amounts of KEtX between 0.008 g/l and 0.15 g/l. It was experimentally proved that the degree of deformation between 83 and 99 % does not have a large effect on the open circuit potential, as well as on the behavior of copper during anodic polarization in 1 M Na2CO3. Voltammograms show no significant differences between peak heights obtained for different electrodes. The first peak which occurs at potential of around -0.06 V vs. SCE corresponds to the formation of copper oxide Cu2O. The second wide peak is at potential of around 0.15 V vs. SCE and corresponds to the formation of CuO. Addition of potassium ethyl xanthate in alkaline 1 M Na2CO3 solution changes the mechanism of the process in anodic part, which is reflected in the change of shape of voltammograms. In presence of KEtX in concentration between 0.008 g/l and 0.15 g/l on voltammograms a sharp peak appears at potential of about -0.2 V vs. SCE and corresponds to the oxidation of xanthate. Current density, which determines the rate of the process which takes place at the electrode surface, yet in the presence of smallest amounts of KEtX (<0,08 g/l) is higher than in the absence of KEtX. It allows one to conclude that the processes of oxidation of copper accelerate in presence of potassium ethyl xanthate.

Study on the Pyrazole Corrosion Inhibition and Synergistic Effect for Copper in Alkaline Solution

Study on the Pyrazole Corrosion Inhibition and Synergistic Effect for Copper in Alkaline Solution

Formation of oxides on copper in alkaline solution and their photoelectrochemical properties

The anodic formation of Cu(I) and Cu(II) oxides on polycrystalline copper in a deaerated alkaline solution is studied using the technique of the synchronous recording of transients of the photocurrent and polarization current. The oxide formation in a currentless mode is analyzed via the synchronous recording of photopotential and corrosion potential. It is found that copper is susceptible to corrosion oxidation due to traces of dissolved oxygen with the formation of a Cu(I) oxide. The preliminary formation of the underlayer of anodic Cu(I) oxide on copper hinders its further corrosion oxidation. It is confirmed that copper oxides Cu2O and CuO, which appear on copper in both anodic and corrosion modes of formation, are p-type semiconductors. The initial stage of anodic oxidation of copper is characterized by the formation of an intermediate compound of Cu(I), possibly CuOH, which exhibits n-type conductivity. A film of Cu(I) oxide is thin and has a band gap of 2.2 eV for indirect optical transitions. Anodic polarization in the range of potentials of CuO formation leads to the formation of a thicker oxide film, which is a mixture of Cu(I) and Cu(II) oxides.

The Effects of Cassia Siamea Lam. Root Extract on the Corrosion and Kinetics of Corrosion Process of Copper in Alkaline Solutions

The effect of Cassia siamea lam. (CSL) root extract as a corrosion inhibitor of copper in 0.50 M NaOH solutions was investigated using absorbance difference technique at 30 °C and 40 °C. CSL root extract inhibited the corrosion of copper in 0.50 M NaOH solutions and the inhibition efficiency (% IE) increased to a maximum of 78.3±2.3% with increasing concentration of the extract but decreased with increasing temperature. The adsorption of CSL root extract on copper surface followed the Langmuir adsorption model with the average heat of adsorption, Qads and free energy of adsorption, ΔGads of ‐8.98 kJmol-1 and ‐8.70 kJmol-1 respectively. A kinetic treatment of the data revealed a first order kinetics with respect to copper in the presence and absence of the extract.

Study of the electroreduction of nitrate on copper in alkaline solution

The electrocatalytic activity of a Cu electrode for the electroreduction of nitrate in alkaline medium was investigated by linear sweep voltammetry at stationary and rotating disc electrodes. Nitrate-reduction products generated upon prolonged electrolyses at different potentials were quantified. In addition, adsorption phenomena associated with the nitrate electroreduction process were characterized by electrochemical quartz crystal microbalance (EQCM) experiments. This data revealed that nitrate electroreduction process strongly depends on the applied potential. Firstly, at ca. −0.9 V vs. Hg/HgO, the electroreduction of adsorbed nitrate anions to nitrite anions was identified as the rate-determining step of the nitrate electroreduction process. Between −0.9 and −1.1 V, nitrite is reduced to hydroxylamine. However, during long-term electrolyses, hydroxylamine is not detected and presumably because it is rapidly reduced to ammonia. At potential more negative than −1.1 V, nitrite is reduced to ammonia. At ca. −1.45 V, i.e. just before the hydrogen evolution reaction, the abrupt decrease of the cathodic current is due to the electrode poisoning by adsorbed hydrogen. In addition, during the first minutes of nitrate electrolysis, a decrease of the copper electrode activity was observed at the three investigated potentials (−0.9, −1.1 and −1.4 V). From polarization and EQCM measurements, this deactivation was attributed to the adsorption of nitrate-reduction products, blocking the electrode surface and slowing down the nitrate electroreduction rate. However, it was demonstrated that the Cu electrode can be reactivated by the periodic application of a square wave potential pulse at −0.5 V, which causes the desorption of poisoning species.

The Nature and Thiknesses of Passive Films on Interface Cu/ NaOH+Alanine

Thicknesses of films formed on the copper in alkaline solution in the presence of alanine are studied by ellipsometric method. It was found that small additives of β-alanine (10-4-10-3 mol/l) cause additional stabilization of copper passivity due to an increase in the film thickness. The adsorption kinetics of α- and β-alanine is studied. It is shown experimentally that β-alanine adsorbs on copper according to the Frumkin isotherm. By contrast, no definite type isotherm can be obtained for α-alanine due to its higher activity and ability to form soluble complexes with copper ions.

Peculiarities of electrochemical behavior of copper in alkaline solutions in the presence of alanine

Anodic oxidation of copper in alkaline solution in the presence of alanine is studied by electrochemical and ellipsometric methods. Thickness of films formed on the metal in the working solutions, are determined. Small additives of β-alanine (10−4–10−3 mol/l) cause additional stabilization of copper passivity due to an increase in the film thickness. The adsorption kinetics of α-and β-alanine is studied. It is shown experimentally that β-alanine adsorbs on copper according to the Frumkin isotherm. By contrast, no definite type isotherm can be obtained for α-alanine due to its higher activity and ability to form soluble complexes with copper ions.

The influence of gelatine on the corrosion behaviour of cold worked copper wire in alkaline media

Copper wire obtained by dip-forming process was cold worked to the deformation degrees of 83, 87, 91, 95 and 99 %. Electrochemical potentiodynamic method was used to investigate corrosion behavior of these wires in aqueous solutions of Na2CO3 (1 mol/dm3). Open circuit potentials as well as peak potentials are given as a function of deformation degree in Na2CO3 without and with addition of gelatine in concentration between 0.1 and 0.5 g/l. It was found that the addition of gelatine does not change the mechanism of the process, but influences on current density. Small concentrations of gelatine (0.1 g/l or less) have positive influence on the corrosion protection of copper in alkaline solution, but the addition of gelatine in concentration 0.5 g/l causes the increasing of its corrosion rate.

Electro-oxidation of methanol on copper in alkaline solution

The electro-oxidation of methanol on copper in alkaline solutions has been studied by the methods of cyclic voltammetry, quasi-steady state polarization and chronoamperometry. It has been found that in the course of an anodic potential sweep the electro-oxidation of methanol follows the formation of Cu III and is catalysed by this species through a mediated electron transfer mechanism. The reaction also continues in the early stages of the reversed cycle until it is stopped by the prohibitively negative potentials. The process is diffusion controlled and the current–time responses follow Cottrellian behavior. The rate constants, turnover frequency, anodic transfer coefficient and the apparent activation energy of the electro-oxidation reaction are reported.

Sonovoltammetric studies on copper in buffered alkaline solution

The effect of ultrasound on the voltammetry of copper in alkaline solution is reported. At pH 7 the electrode surface remains active after scanning to ca. +1.0 V (vs. SCE) and the effects of ultrasound show the expected substantial enhancement in limiting current due to improved mass transport under ultrasound. However at pH 9, whereas the silent scan is only slightly altered in gross detail from that obtained at pH 7, the sonicated scan is significantly different. This shows the expected current increase only up until ca. +0.6 V (vs. SCE), where there is a substantial loss of current showing a passivation phenomenon that is enhanced by ultrasound. In addition, during the reverse (reduction) scan under ultrasound an anodic peak appears. This suggests reactivation of the electrode during the cathodic sweep, possibly by reductive removal of a transient species from the electrode/(hydr)oxide interface at a potential where oxidation still occurs. Increasing the pH to 11 further shifts the cathodic peaks in the silent voltammogram.