Investigation of copper corrosion inhibition by STM and EQCM techniques

The mechanism of copper corrosion and its inhibition were studied using electrochemical techniques, in situ scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM) methods. The morphological changes of Cu (111) were followed in 0.1 M Na₂SO₄ solution at pH 2.95. The adsorption of 5-mercapto-1-phenyl-tetrazole (5-McPhTT) at different concentrations was studied. The anodic dissolution of copper in 0.1 M Na₂SO₄ was clearly modified and hindered by the addition of 5-McPhTT. The anodic current density was reduced sharply due to the adsorption of the inhibitor on the metal surface thus providing protection. EQCM data revealed that the addition of the inhibitor to the aggressive solution did not cause a continuous increase in the electrode mass. This fact indicates that the inhibitor effect in hindering copper corrosion was due to the adsorption of a monolayer or even a submonolayer.     

Protection of copper corrosion by carbazole and N-vinylcarbazole self-assembled films in NaCl solution

Self-assembled films of carbazole (CZ) and N-vinylcarbazole (NVC) were prepared on copper surfaces. The corrosion protection abilities of the films were evaluated in an air-saturated 0.5 mol dm^–3 NaCl solution using electrochemical impedance spectroscopy (EIS), polarization and cyclic voltammetry. The results indicate that CZ and NVC form dense protective films on copper. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the film. It was found that the NVC molecules are tilted at an angle to the copper surface. The theoretical ab initio calculations support the experimental results.     

Electrochemical investigation of copper oxide films formed by oxygen plasma treatment

Linear potential sweep voltammetry was used to characterize the copper oxides grown on a metal substrate when exposed to a low pressure inductively coupled oxygen plasma. This study confirms the formation of a precursor oxide CuxO (x > 4), two copper(i) oxides Cu2-xO and Cu3O2 and copper(ii) oxide CuO. The electrochemical reduction curve of CuxO is characterized in aqueous solution (pH 9.2) by a minor peak near –0.5V vs SCE while the two Cu(i) oxides present one reduction peak at –0.8 VvsSCE and cannot be electrochemically separated; CuO is reduced to Cu(i) at –0.65V vs SCE. The reduction potentials of the copper(i) and copper(ii) oxides vary with the oxide layer thickness which increases with the time of exposure to the plasma and the injected electric power and decreases as the distance between the sample and the 1st coil increases for given treatment parameters. In addition, a mechanism is proposed for the reduction of thin films containing the copper(i) and copper(ii) oxides formed after plasma treatment.     

超厚氧化皮铜及铜合金零件的表面处理

铜及铜合金制品经高温氧化后氧化皮过厚，进行化学抛光处理难度较大。研制出易于操作的低污染快速脱膜一低污染化学抛光一无铬高效钝化工艺，介绍了以上三道工序的规范、溶液配置及维护、工艺条件的影响。该工艺用于超厚氧化皮铜及铜舍金零件表面处理，效果较好。     

The uneven corrosion of deep drawn coil-coatings investigated by EIS

The corrosion distribution along a coil-coating sample formed by deep-drawing is reported. The formed rectangular cup was divided in five different regions and their impedance response investigated independently. The response of each region was compared with the overall sample response and the morphology of degradation was studied by scanning electron microscopy. Severe attack was observed in the most strained regions (corners and edges). Micro-defects in the shape of pinholes and cracks developed as a consequence of the forming process, apparently nucleating in the vicinity of the inorganic particles present in the paint. Immersion increased the size and number of defects. The overall impedance was reconstructed from the impedance measured in the local regions by two methods: (a) calculation using the local experimental data and (b) simulation using an equivalent electrical circuit with the values taken from the fitting of the local experimental data.     

Growth of anodic oxide films on oxygen-containing niobium

The present study is directed at understanding of the influence of oxygen in the metal on anodic film growth on niobium, using sputter-deposited niobium containing from about 0-52 at.% oxygen, with anodizing carried out at high efficiency in phosphoric acid electrolyte. The findings reveal amorphous anodic niobia films, with no significant effect of oxygen on the field strength, transport numbers, mobility of impurity species and capacitance. However, since niobium is partially oxidized due to presence of oxygen in the substrate, less charge is required to form the films, hence reducing the time to reach a particular film thickness and anodizing voltage. Further, the relative thickness of film material formed at the metal/film interface is increased by the incorporation of oxygen species into the films from the substrate, with an associated altered depth of incorporation of phosphorus species into the films.     

Morphological and structural studies of nanoporous nickel oxide films fabricated by anodic electrochemical deposition techniques

Porous nickel oxide films are directly deposited onto conducting indium tin oxide coated glass substrates by cyclic voltammetric (CV), galvanostatic, and potentiostatic strategies in a plating bath of sodium acetate, nickel sulfate, and sodium sulfate. By tuning the deposition parameters, it is possible to prepare nickel oxide films with various morphologies and structures. Film formation relies on the oxidation of dissolved Ni²⁺ to Ni³⁺, which further reacts with the available hydroxide ions from a slightly alkaline electrolyte to form insoluble nickel oxide/hydroxide deposits on the substrate. A compact film with particularly small pores is obtained by CV deposition in a potential range of 0.7-1.1 V. A galvanostatically deposited film is structurally denser near the surface of the substrate, and becomes less dense further away from the surface. Interestingly, a potentiostatically deposited film has pores distributed uniformly throughout the entire film. Therefore, for obtaining a uniform film with suitable pore size for electrolyte penetration, potentiostatic deposition technique is suggested. In addition, except for CV deposition, the deposited films resemble closely to cubic NiO when the annealing temperature exceeds 200 °C.     

Growth and structural characteristics of perovskite-wurtzite oxide ceramics thin films

Wurtzite ZnO thin films were grown on single-crystal perovskite SrTiO₃(STO) (1 0 0) substrates at various temperatures. The ZnO/STO thin films thus formed exhibit a preferred (1 1 0)-orientation at a growth temperature of 600-700 °C. A high growth temperature enhances not only the (1 1 0)-texture of ZnO/STO thin films but also the crystalline quality of the film. (La_0.7Sr_0.3)MnO₃ (LSMO) thin films were subsequently grown on ZnO(1 1 0)/STO(1 0 0) substrates with various thicknesses, and were polycrystalline. A thicker LSMO film has a stronger (0 0 l)-preferred orientation than the thinner one. The lattice distortion of LSMO decreases as the LSMO thickness increases. Magnetization vs. temperature curves show that both crystalline quality and lattice distortion influence the magnetic properties of LSMO thin films. The physical properties of the manganite oxide can be modulated by forming a heterostructure with wurtzite ZnO.     

Photoelectrochemical kinetics of Eosin Y-sensitized zinc oxide films investigated by scanning electrochemical microscopy under illumination with different LED

The overall efficiency of the light-induced charge separation in dye-sensitized solar cells depends on the kinetic competition between back electron transfer and dye regeneration processes by a redox electrolyte. In a previous study, the reduction of the intermittently formed photo-oxidized dye molecules by iodide ions in the electrolyte phase was investigated using the feedback mode of a scanning electrochemical microscope (SECM) and a quantitative model had been derived. Here we provide a more thorough experimental verification of this model by variation of the excitation wavelength, light intensities and mediator concentrations. Nanoporous ZnO/Eosin Y films prepared by self-assembly were used as model electrodes and were used with an iodide/triiodide electrolyte. The experimentally found effective rate constants could be related to the rate constant for the reaction of the dissolved donor with photo-oxidized Eosin Y bound to ZnO and the absorption spectrum of the dye and confirmed the assumption made in the derivation of the model. For the regeneration process of Eosin Y, a rate constant of k_ox with different light emitting diodes and light intensities is determined.     

Composition and structure of copper oxide films synthesized by reactive magnetron sputtering with a hot target

The influence of the target operation mode on the chemical composition and crystalline structure of copper oxide films deposited onto a quartz glass substrate has been studied using Raman spectroscopy and X-ray phase analysis. The films have been synthesized in an Ar + O₂ gaseous environment using two identical magnetrons, differing only by the method of target cooling.     

Adhesion of gold and copper thin films deposited on alumina and magnesium oxide

Scratch and pull-off methods for adhesion measurement were applied to various film/ substrate systems. The film crystallographic structure was investigated by transmission electron microscopy (TEM) in order to correlate it to the adhesion strength. We also correlate the film and substrate electronic structures (in particular the electronegativity) to the adhesion strength. The results of adhesion measurement are also discussed with respect to the substrate temperature. The main results are that the adhesion strength is greater when the film is deposited on magnesium oxide than on alumina substrates, and for the copper than for the gold deposit. Also, the adhesion strength increases with the substrate temperature.     

Electrochemical synthesis and characterization of poly(m-phenylenediamine) films on copper for corrosion protection

Poly(m-phenylenediamine) (PMPD) films were electrosynthesized on copper by using cyclic voltammetry in near-neutral aqueous sodium oxalate medium. Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy, scanning electron microscopy and atomic force microscopy were utilized to characterize the obtained PMPD films. Corrosion performances of uncoated and PMPD coated copper electrodes were investigated in 0.1 M H₂SO₄ by open circuit potential–time (E_ocp–t) curves, anodic polarization and electrochemical impedance spectroscopy techniques. Corrosion test results demonstrate that the PMPD coating appears to enhance protection of copper for considerable immersion periods. The percent protection efficiency value (E%) was found to be 80% even after 168 h immersion time in corrosive test solution.     

Self-assembled 1-octadecyl-1H-1,2,4-triazole films on copper for corrosion protection

A film of 1-octadecyl-1H-1,2,4-triazole (OTA) was formed on a fresh copper surface by self-assembly technique. The optimum concentration of OTA and immersion time for the formation of a protective OTA film have been established using electrochemical impedance spectroscopy (EIS). These are (i) 15 mM concentration of OTA in methanol and (ii) immersion period of 48 h. X-ray photoelectron spectroscopy (XPS), reflection absorption FTIR spectroscopy, atomic force microscopy (AFM), and contact angle measurements have been used to characterize the OTA film on copper surface. The efficiency of OTA film to protect copper from corrosion in aqueous NaCl environment has been investigated using EIS, potentiodynamic polarization studies, cyclic voltammetry and weight-loss studies. All these studies showed that the OTA film affords excellent protection against corrosion of copper.     

An overview of techniques for characterizing inhomogeneities in organic surface films and underfilm localized corrosion

This paper presents an overview of techniques for characterizing inhomogeneities in various forms of organic surface films including organic coatings, corrosion inhibitor and anti-corrosion oil films, and for understanding the effects of surface film inhomogeneities on underfilm localized corrosion. Particular focus is on technological innovations that have been made over the past two decades, including scanning probe techniques and the wire beam electrode method.     

Fluorinated a-C:H films investigated by thermal-induced gas effusion

Using thermal-induced gas effusion the decomposition of plasma deposited fluorinated a-C:H films has been investigated. The main contributions to the effusion spectra were found to come from hydrogen, hydrocarbons, CF₄ and HF. It is observed that hydrogen-related effusion is progressively substituted by the effusion of CF₄-related species as the fluorine content is increased, confirming that fluorine atoms substitute hydrogen in the amorphous network. At low fluorine contents (<10 at.%) the material is relatively compact and the effusion of hydrogen-related species (hydrogen molecules and hydrocarbons) dominate. For high enough fluorine concentrations a strong change in the effusion characteristics indicates that an interconnected network of voids is present. Strong effusion of CF₄-related species is found to be consistent with a surface desorption process and can be observed when CF_n bonds are present in the film microstructure and the void network dimensions are large enough, i.e. for films with the highest fluorine contents (∼20 at.%). The effusion results can be correlated to a structural transition from diamond-like to polymer-like film.     

Corrosion protection of copper by polyaminophenol films

The anticorrosion behaviour of polyaminophenol (PAP) films has been investigated in aqueous 0.5 M NaCl solution using electrochemical impedance spectroscopy and weight loss measurements. The effect of triazole compounds on the protection behaviour of the polymer was also examined. The polymer is obtained by in situ electropolymerization of 2-aminophenol monomer in alkaline hydroalcoholic solution. The results show that the polymer film reduces the corrosion of copper and that the electropolymerization in the presence of the azole compounds further increases the protective character of the coating. The polymer copper/solution interface is well described by an electrical equivalent circuit reflecting the behaviour typical of a porous film.     

Physicochemical and biological properties of electrodeposited graphene oxide/chitosan films with drug-eluting capacity

In this study, novel graphene oxide/chitosan nanocomposite coatings with long term drug-eluting potential are presented. The coatings are fabricated by the facile and reproducible electrophoretic deposition technique. Analysis of the prepared films shows that the graphene oxide nanosheets are exfoliated in the chitosan matrix. Fourier-transform infrared spectrometry reveals polymer attachment to the carboxylic bonds of graphene oxide, providing a strong interaction and exfoliation of the nanolayers. In vitro viability assay by human osteosarcoma cells (MG-63) demonstrates that the nanocomposite films are highly biocompatible up to 30 wt% graphene oxide, but at higher concentrations a slight cytotoxicity is noticed. Alkaline phosphates enzyme assay also reveals that the presence of graphene oxide nanosheets moderately hampers osteogenesis of the cultured cells. It is shown that vancomycin-loaded nanocomposite coatings gradually release the drug macromolecules for relatively long period of time (up to 4 weeks). The electrodeposited films also exhibit a high bactericidal potential against Gram-positive Staphylococcus aureus. Effects of graphene oxide nanosheets on the physicochemical, biological, antimicrobial and drug-eluting properties of electrodeposited chitosan films are presented and discussed. It is shown that the GO/CS films support the initial attachment, proliferation and growth of osteoblast-like cells.     

Growth of porous type anodic oxide films at micro-areas on aluminum exposed by laser irradiation

Aluminum covered with pore-sealed anodic oxide films was irradiated with a pulsed Nd-YAG laser to remove the oxide film at micro-areas. The specimen was re-anodized for long periods to examine the growth of porous anodic oxide films at the area where substrate had been exposed by measuring current variations and morphological changes in the oxide during the re-anodizing. The chemical dissolution resistance of the pore-sealed anodic oxide films in an oxalic acid solution was also examined by measuring time-variations in rest potentials during immersion.The resistance to chemical dissolution of the oxide film became higher with increasing pore-sealing time and showed higher values at lower solution temperatures. During potentiostatic re-anodizing at five 35-μm wide and 4-mm long lines for 72 h after the film was removed the measured current was found to increase linearly with time. Semicircular columnar-shaped porous type anodic oxide was found to form during the re-anodizing at the laser-irradiated area, and was found to grow radially, thus resulting in an increase in the diameter. After long re-anodizing, the central and top parts of the oxide protruded along the longitudinal direction of the laser-irradiated area. The volume expansion during re-anodizing resulted in the formation of cracks, parallel to the lines, in the oxide film formed during the first anodizing.     

A robust method of enhancement of corrosion inhibitive ability of electrodeposited poly-3-amino-5-mercapto-1,2,4-triazole films over copper surface using graphene oxide

Abstract

A simple and new strategy has been developed to protect metallic copper by forming composite material using graphene oxide (GO) and electropolymerised p-3-amino-5-mercapto-1,2,4-triazole (p-AMTa). The structure and the mechanism of the formation of the polymer and polymer composite were predicted from Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopic (XPS) analysis and Energy Dispersive X-ray (EDX) spectroscopy. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies (PDS) were employed to study the corrosion inhibitive action of p-AMTa?+?GO composite in 3.5% NaCl medium. The study revealed that, the copper electrode modified with the carbon based polymeric composite suppressed the anodic dissolution of copper thereby increasing its corrosion resistance.