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The blistering of epoxy coating and its evolution were investigated after being exposed to 3.5 wt% NaCl solution. The evolution of under-film corrosion could be divided into four stages according to the observation of the corrosion morphology and the distribution of corrosion products and elements. Corrosion propagation was related to the distribution of media at the edge of the blistering area. Local electrochemical impedance spectroscopy analysis revealed that local impedance mapping could help in predicting the direction of corrosion propagation. The interfacial debonding at the edge of the blistering area was a necessary condition for corrosion propagation. [ABSTRACT FROM AUTHOR]

In order to explore the wide application of AM60B in automobile field, nano-SiC/micro-arc oxidation (MAO) composite coating layer was prepared on the surface of AM60B to improve its high-temperature corrosion resistance. The electrochemical properties were studied in different temperature environments (ambient temperature (ABM), 60, 80, and 100 °C) using potentiodynamic polarization tests. The local corrosion properties were evaluated in 3.5% NaCl solution using Localized Electrochemical Impedance Spectroscopy (LEIS). The global electrochemical test results show that the impedance of nano-SiC/MAO coating is 1~2 orders of magnitude higher than that of MAO coating in high-temperature corrosion environment, and the main corrosion product is Mg(OH)2. The local electrochemical test results show that the minimum impedance of nano-SiC/MAO coating is 2×105 Ω higher than that of MAO coating, and the longitudinal depth and transverse width of scratch expansion are smaller than that of MAO coating. The scratch coating still has a protective effect on the substrate. The corrosion physical model of nano-SiC/MAO coating with scratches is proposed. [ABSTRACT FROM AUTHOR]

In this paper, friction stud welding technology was used to join a stud and base metal, which were composed of X65 steel. The scanning vibrating electrode technique (SVET) and localized electrochemical impedance spectroscopy (LEIS) were used to investigate the localized corrosion behaviors of the welded joint. Scanning electron microscopy, metallographic microscopy and a micro-hardness tester were used to observe the microstructure and measure the hardness of the welded sample. Raman spectrometry and energy-dispersive spectrometry were used to measure the composition of the weldment before and after corrosion, respectively. The results show that there are the maximum micro-hardness and the densest microstructure in the welded zone compared with the other zones. In addition, α-Fe2O3 and Fe3O4 are present in the welded zone. The SVET and LEIS data indicate that the welded zone has the lowest current density and the largest impedance due to the presence of iron oxides and the densest microstructure, thus showing the excellent corrosion resistance. The relationship among microstructure, micro-hardness, chemical composition and local electrochemical behavior was discussed. [ABSTRACT FROM AUTHOR]

The effect of immersion time and chloride ion concentration on the early stage of corrosion behavior of scratched epoxy-coated carbon (SM) and chromium containing low-alloy steel (H5) samples were investigated in an in situ manner using localized electrochemical impedance spectroscopy. The results revealed that, the H5 samples had significantly higher impedance values than the SM, which indicated higher corrosion resistance of H5 samples. The drop in impedance magnitude was observed for higher Cl ion concentration, which indicated that breakdown of passive film had been initiated by Cl ion resulting in localized corrosion attack of the surface. The morphological and elemental studies showed the formation of green rust and a very stable hydroxide (CrFe(OH)) on SM and H5 surface respectively as a corrosion product. Hence, the H5 could be a hopeful material with extremely high corrosion resistance for the use as steel structures. [ABSTRACT FROM AUTHOR]

In the present work, sodium phosphomolybdate, an environmentally friendly corrosion inhibitor with good anticorrosive behavior when applied on steel substrates, has been loaded and encapsulated in mesoporous silica nanoparticles without and with a hollow core in order to produce different smart nanocontainers. These nanocontainers have been designed to allow controlled release of the inhibitor in response to an external stimulus, thereby achieving more efficient and more economical use of the active substance. Corrosion activity leads to local changes in pH, and this work considers such changes as a signal of great interest. The nanocontainers respond to a pH of 10 or higher by increasing the release rate of the encapsulated active material. The smart nanocontainers have been incorporated into hybrid organic-inorganic sol-gel coatings and applied on carbon steel substrates. Mechanical defects have been made in the organic coating, reaching through to the metallic substrate, in order to study anticorrosive behavior in the affected area. A characterization study has been carried out at the defects and in their surroundings by means of two different localized electrochemical techniques: Scanning Kelvin Probe and Localized Electrochemical Impedance Spectroscopy. The results have shown significant improvement in the anticorrosive behavior of sol-gel coatings when formulated with smart nanocontainers loaded with sodium phosphomolybdate compared to a reference sol-gel coating. [ABSTRACT FROM AUTHOR]

Defective epoxy varnish and hydrofluoric acid-doped polyaniline/epoxy (PANI-HF/EP) coatings were coated on the surface of an AZ91D magnesium alloy. The corrosion protection of the defective coatings was evaluated in 0.05 M NaCl by localized electrochemical impedance spectroscopy. Then, the surface of AZ91D magnesium alloy beneath the coating was analyzed by scanning electron microscopyand energy dispersive X-ray spectroscopy. The results indicated that the defective epoxy varnish coating could not protect the magnesium alloy because it only served as an electrolyte barrier. By contrast, the PANI-HF/EP coating served not only as an electrolyte barrier, but also facilitated the formation of a protective layer by redox processes. Therefore, the defective PANI-HF/EP coating could protect magnesium alloy from corrosion. [ABSTRACT FROM AUTHOR]

The increase of the accuracy of optical frequency standards by means of the development of nuclear clocks a novel frequency standard based on the nuclear transition to the long-living isomer nuclear state of Th-229 with energy ~7.6 eV is of great interest. The main problem is the fact that there are no experimental data on the direct measurement of the energy of the isomeric transition in Th-229, and the above result was obtained only by indirect measurements, and has great uncertainty. Low energy ion scattering spectroscopy might be used for more precision investigations of the isomeric transition in Th-229. It is caused by the fact that ion scattering spectra exhibit the fine structure determined by the target surface electronic structure. In the case of low energy nuclear transition it can give the information about the isomer nuclear state of Th-229. To prove this supposition it is necessary to prepare high quality samples with a high thorium surface coverage. An original preparation technique of the thorium films by electrochemical deposition from thorium nitrate solution on Si(111) substrate is reported. It was found that electrochemical deposition of Th on the semiconductor substrates leads to the formation of ThSiO island films. The origin of the observed thorium films formation and the results on the investigation of Th and Th films on Si(111) surface by X-ray photoelectron spectroscopy and low energy ion spectroscopy discussed. [ABSTRACT FROM AUTHOR]

This document is part of Subvolume A of Volume 45 'Physics of Solid Surfaces' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains an overview of the low-energy ion scattering technique used in surface layer analysis. Parent documents: SpringerMaterials Volume III/45A General introduction to Volume III/45A [ABSTRACT FROM AUTHOR]

Smart epoxy coatings modified with different additives were applied on AA2024. The following three different systems were studied: a reference consisting of an epoxy coating containing chromate active pigments and two 'smart' coatings modified with containers loaded with corrosion inhibitor-layered double hydroxides filled with mercaptobenzothiazole and tubular halloysites (HS) filled with 8-hydroxyquinoline. The thickness of the coatings was determined by scanning electron microscopy. The barrier properties and the average corrosion resistance were assessed by electrochemical impedance spectroscopy (EIS). The long-term corrosion repair ability of the various coatings was confirmed by EIS measurements carried for a period of 3 weeks in scratched samples. The ability of the smart additives to inhibit corrosion over defects with different sizes and geometry was studied at the microscale by using localized impedance spectroscopy (LEIS) and the scanning vibrating electrode technique. The results demonstrate that the additives provide effective corrosion inhibition on defects of various sizes. Moreover, the LEIS measurements give some important highlights concerning the mechanisms and kinetics of inhibition of each system. [ABSTRACT FROM AUTHOR]

The determination of the mass transport kinetics of oxide materials for use in electrochemical systems such as fuel cells, sensors and oxygen separators is a significant challenge. Several techniques have been proposed to derive these data experimentally with only the oxygen isotope exchange depth profile technique coupled with secondary ion mass spectrometry (SIMS) providing a direct measure of these kinetic parameters. Whilst this allows kinetic information to be obtained, there is a lack of knowledge of the surface chemistry of these complex processes. The advent of low-energy ion scattering (LEIS) now offers the opportunity of correlating exchange kinetics with chemical processes at materials atomic surfaces, giving unprecedented levels of information on electrochemical systems with isotopic discrimination. Here, the challenges of these techniques, including sample preparation, are discussed and the advantages of the combined approach of SIMS and LEIS illustrated with reference to key literature data. [ABSTRACT FROM AUTHOR]

Model catalysts consisting of Au and Ag clusters of varying size have been prepared on single crystal TiO2(110) and ultra-thin films of TiO2, SiO2 and Al2O3. The morphology, electronic structure, and catalytic properties of these Au and Ag clusters have been investigated using low-energy ion scattering spectroscopy (LEIS), temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) and spectroscopy (STS) with emphasis on the unique properties of clusters <5.0 nm in size. Motivating this work is the recent literature report that gold supported on TiO2 is active for various reactions including low-temperature CO oxidation and the selective oxidation of propylene. These studies illustrate the novel and unique physical and chemical properties of nanosized supported metal clusters. [ABSTRACT FROM AUTHOR]

A modernized setup for studying the ion-surface interaction is briefly described. The main ion channel implemented on the “Large MEPhI mass monochromator” with an ion energy range of 1–40 keV makes it possible to obtain ion beams with ( EM/Z) ≤ 4000 keV × a.m.u. Operation with intermediate-energy hydrogen ions allows obtaining information on the thickness of layers of atoms with masses differing from substrate atoms, by analyzing energy spectra of protons scattered from two- or three-layer targets. The use of new digital power units and relevant control programs also allows automation of the ion beam control and makes it possible to perform ion-beam experiments using preliminarily developed irradiation programs. [ABSTRACT FROM AUTHOR]