Matjaž Finšgar

Surface Analysis of 1-Hydroxybenzotriazole and Benzotriazole Adsorbed on Cu by X-Ray Photoelectron Spectroscopy

The surface chemistry of two corrosion inhibitors, 1-hydroxybenzotriazole (BTAOH) and benzotriazole (BTAH), adsorbed on copper from 3% NaCl aqueous solution, was investigated by X-ray photoelectron spectroscopy (XPS). Surface and subsurface chemical structure, composition, and layer thickness were obtained from angle-resolved XPS measurements, from detailed analysis of the background in the XPS spectra by the Tougaard method, and from XPS depth profiling performed by Ar-ion sputtering. The main concern was the shape of the X-ray induced Auger Cu L 3 M 4,5 M 4,5 spectrum that offers the possibility to investigate the Cu(I) environment. The Auger Cu L 3 M 4,5 M 4,5 spectrum obtained after treatment in the BTAH-containing solution was decomposed into three components originating from the Cu(I)BTA complex layer, the Cu 2 O underlayer, and the Cu substrate. This procedure indicates the formation of the Cu(I)BTA surface complex on the Cu 2 O underlayer after BTAH treatment. The BTAH molecules [either in the Cu(I)BTA complex or uncomplexed] are directed toward the Cu surface through their triazole N atoms. In contrast to the BTAH treatment, the Cu-BTAOH layer formed on the Cu surface after treatment in the BTAOH solution is less ordered and is much thinner than the Cu-BTAH structure.

Determination of the Cu2O Thickness on BTAH-Inhibited Copper by Reconstruction of Auger Electron Spectra

The influence of the benzotriazole (BTAH) inhibitor on the thickness of the Cu 2 O oxide layer formed on Cu immersed in 3% NaCl solution was studied with angle-resolved X-ray photoelectron spectroscopy. The X-ray-induced Auger Cu L 3 M 4.5 M 4,5 spectra were reconstructed with the Monte Carlo algorithm using the spectra of the basic constituents [Cu(I)BTA, Cu 2 O, and Cu] formed on the surface. The relative contributions of the basic constituents to the composite Cu L 3 M 4,5 M 4,5 spectra measured at different emission angles were then used to estimate the thickness of the Cu 2 O oxide layer. The results show that the presence of BTAH substantially reduces the thickness of the Cu 2 O oxide layer formed on Cu in chloride media. The average thickness of the Cu 2 O layer below the Cu(I)BTA layer is estimated to be 1.3 ± 0.2 nm, whereas the Cu 2 O thickness of the noninhibited sample is 2.2 ± 0.3 nm.

Triazole, Benzotriazole, and Naphthotriazole as Copper Corrosion Inhibitors: I. Molecular Electronic and Adsorption Properties

The gas-phase adsorption of 1,2,3-triazole, benzotriazole, and naphthotriazole-considered as corrosion inhibitors-on copper surfaces was studied and characterized using density functional theory (DFT) calculations. We find that the molecule-surface bond strength increases with increasing molecular size, thus following the sequence: triazole<benzotriazole<naphthotriazole. This trend is explained in terms of molecular electronegativity and chemical hardness, which decrease monotonously as the molecular size increases. While the electronegativity of triazole is almost degenerate with the work function of Cu(111) surface, the electronegativity of larger acenotriazoles is smaller. The difference in electronegativity between the Cu(111) and the acenotriazoles thus increases with increasing the molecular size, which, together with decreasing the molecular hardness, results in larger molecule-to-metal electron charge transfer and stronger molecule-surface bonds.

Novel chitosan/diclofenac coatings on medical grade stainless steel for hip replacement applications

Corrosion resistance, biocompatibility, improved osteointegration, as well the prevention of inflammation and pain are the most desired characteristics of hip replacement implants. In this study we introduce a novel multi-layered coating on AISI 316LVM stainless steel that shows promise with regard to all mentioned characteristics. The coating is prepared from alternating layers of the biocompatible polysaccharide chitosan and the non-steroid anti-inflammatory drug (NSAID), diclofenac. Electrochemical methods were employed to characterize the corrosion behavior of coated and uncoated samples in physiological solution. It is shown that these coatings improve corrosion resistance. It was also found that these coatings release the incorporated drug in controlled, multi-mechanism manner. Adding additional layers on top of the as-prepared samples, has potential for further tailoring of the release profile and increasing the drug dose. Biocompatibility was proven on human-derived osteoblasts in several experiments. Only viable cells were found on the sample surface after incubation of the samples with the same cell line. This novel coating could prove important for prolongation of the application potential of steel-based hip replacements, which are these days often replaced by more expensive ceramic or other metal alloys.

Mechanically strong, flexible and thermally stable graphene oxide/nanocellulosic films with enhanced dielectric properties

Flexible and eco-friendly films, with enhanced dielectric properties and the potential for energy storage applications, have been fabricated from ammonia-functionalized graphene oxide (NGO) nanoplatelets and wood-based cellulose nanofibrils (CNF) vs. (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) pre-oxidized (carboxylated) CNFs (TCNF) by the solvent casting method. Various CNF-NGO (CNG) and TCNF-NGO (TCNG) composite films prepared with 0.5–3 wt% of NGO were analysed structurally by FTIR and XRD spectroscopy, and evaluated optically by UV-Vis spectroscopy. The morphological analysis using SEM showed good dispersibility of the NGO sheets in the randomly-distributed CNF, and the dense and parallel-oriented TCNF cellulose nanofibrils. Such a synergistic effect of both components contributed to ultra-strong and ultra-stiff composite films with good mechanical and thermal stability, although they were more brittle with a smoother surface and lower transmittance for the TCNF based films, due to the stronger physico–chemical interactions with NGO. The dielectric performance was verified with a higher (3 wt%) NGO loading capacity, which resulted in a dielectric constant of ∼46 vs. ∼52, and conductivity of ∼2.07 × 10−4 S m−1 vs. 3.46 × 10−4 S m−1 for CNG vs. TCNG films, respectively, at a frequency of 1 MHz, showing greater enhancement than other reported studies. Cyclic voltammetry and electrochemical impedance studies reveal the energy storage ability and electrochemical performance of the composite films, under kinetic- and diffusion-controlled processes for the CNG, and under a kinetic-controlled process for the TCNG films.

Green corrosion inhibitors for aluminium and its alloys: a review

This review summarises the research work published in the last two decades on the use of natural compounds as corrosion inhibitors for aluminium and aluminium alloys in different solutions. Herein, plant extracts, gums, drugs, and oils have been considered as green corrosion inhibitors. The advantages and disadvantages of the methods used to obtain green corrosion inhibitors are presented. Additionally, the inhibition effectiveness of these corrosion inhibitors, including the techniques used to evaluate them and the respective inhibition mechanisms, are discussed. Finally, a critical evaluation is presented together with the outlook as regards possible future improvements.

Organic corrosion inhibitors for aluminium and its alloys in acid solutions: a review

The aim of this review is to summarise the research work published in the last two decades on the use of organic compounds as corrosion inhibitors for aluminium and its alloys in acidic solutions. The focus is on HCl and H2SO4 solutions due to their extensive use in different applications, such as chemical and electrochemical etching, acid cleaning, anodising, and acid pickling of aluminium. Other acids are also reviewed. The inhibition effectiveness of numerous organic compounds and their possible inhibition type and mechanism are also discussed. Electrochemistry is mainly used to investigate inhibitor performance.

Novel ethanol-induced pectin–xanthan aerogel coatings for orthopedic applications

In this study, we developed a novel high methoxyl pectin-xanthan aerogel coating on medical-grade stainless steel, prepared by ethanol-induced gelation and subsequent supercritical drying. Two non-steroidal anti-inflammatory drugs, i.e. diclofenac sodium and indomethacin, were incorporated into the aerogel coating. Electrochemical analyses were performed on the coated samples using electrochemical impedance spectroscopy and cyclic polarization techniques. The results showed that all passivated samples were highly resistant to general corrosion. The release of both non-steroidal anti-inflammatory drugs was complete after 24h, as confirmed by the plateau in the drug release profiles as well as by IR spectroscopy after the final release point. The potential of samples for use in orthopedic applications was evaluated on a human bone-derived osteoblast cell and all samples were shown to be biocompatible. The increased viability of some samples indicates the high potential of the developed approach for future evaluation of possible clinical use.

The first X-ray photoelectron spectroscopy surface analysis of 4-methyl-2-phenyl-imidazole adsorbed on copper

This article focuses on a detailed surface analytical study by X-ray photoelectron spectroscopy (XPS) of 4-methyl-2-phenyl-imidazole (MePhI) adsorbed from 3 wt% NaCl solution on a Cu surface. It is shown for the first time that MePhI is a Cu corrosion inhibitor in chloride solution after short-term (1–100 h) and long-term immersion periods (180 days), and that MePhI is an anodic-type corrosion inhibitor. Surface analysis was first performed by examination of the Cu surface layer chemical structure, followed by the analysis of the surface layer thickness according to the Tougaard method. It is shown that a very thin layer is formed. Next, a detailed angle-resolved XPS analysis was performed to study the manner of MePhI bonding on the copper surface. It is claimed that the MePhI molecule connects to the surface via C and N atoms. A flat orientation of MePhI molecules, parallel to the copper surface, is suggested.

The first electrochemical and surface analysis of 2-aminobenzimidazole as a corrosion inhibitor for copper in chloride solution

For the first time, 2-aminobenzimidazole (2-ABI) was tested as a corrosion inhibitor for copper in 3 wt% NaCl solution at 25 °C using cyclic voltammetry (CV), chronopotentiometry, electrochemical impedance spectroscopy (EIS), and potentiodynamic curve (PD) techniques. The EIS measurements indicated that the corrosion of Cu in the presence of 2-ABI followed kinetic- and diffusion-controlled processes. After 100 h of immersion, the potentiodynamic curves showed that 2-ABI acts as a mixed-type inhibitor, with a predominant action on the anodic corrosion reaction. ATR-FTIR confirmed the adsorption of 2-ABI on the Cu surface, which resulted in increased hydrophobicity of the copper surface and reduced its surface roughness.