Recent developments in characterising electrodeposition of anti-corrosion coatings using the wire beam electrode method

New progresses have been made during recent years in the application of the wire beam electrode (WBE, a coupled multielectrode array) for studying electroplating of metallic coatings, for monitoring the electrodeposition of polymer coatings, and for evaluating the performance of anti-corrosion coatings. The WBE allows localized electrode processes to occur over different locations of its surface under external anodic or cathodic polarization and permits monitoring of nonuniform electrodeposition processes. Several typical experiments are presented in this paper. One sample experiment is the characterization of nonuniform electroplating of nickel coating, which was achieved by mapping the distributions of currents over a WBE surface that was under cathodic polarization. Various characteristic current distribution patterns, which indicate different electrodeposition mechanisms or low covering-power, have been observed. These patterns were found to correlate with the effects of several affecting factors such as electrolyte concentration, temperature and agitation flow. Another sample experiment is the investigation of nonuniform anodic electrodeposition of polyaniline (PANI) coatings and the understanding of their anti-corrosion performance and mechanisms. Anodic polarization currents were measured from various locations over the WBE surface in order to produce anodic polarization current maps under PANI deposition.

The Effect of Coating Patterns with Spinel-Based Investment on the Castability and Porosity of Titanium Cast into Three Phosphate-Bonded Investments

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Filmes de titânio-silício preparados por spin e dip-coating

The conditions for the preparation of luminescent materials, consisting of Eu3+ ions entrapped in a titanium matrix, in the forma of a thin film, using the sol-gel process, are described. The films were obtained from sols prepared with TEOS and TEOT, in the presence of acetylacetone as the hidrolysis-retarding agent, using the dip-coating and spin-coating techniques. The influence of these techniques on the films based on titanium and silicon are presented. The Eu3+ was used as a luminescent probe. The films have been characterized by luminescence, reflection and transmittance. The thickness of the films could be related to the preparation procedure. Transparent thin films have been prepared by dip-coating technique.

Comparative study of the clinical and anti-microbial efficacy of tongue cleaners

Candida species have frequently been isolated from the oral cavities of a variety of patients, such as elderly people, dentures users, immunocompromised and health patients. Yeasts may be associated with immune response and local factors such as poor oral hygiene. It was evaluated effectiveness of tongue cleaner showing which types would be preferred by patients, changes in tongue coating and in saliva yeasts counting. Thirty patients were selected and randomly distributed into three groups. This crossover blind study evaluated the effect of tongue cleaning using: a plastic and a steel tongue scraper and a nylon soft-bristle toothbrush. All patients were instructed to use the cleaners twice a day for one week (fifteen-day wash-out period). Saliva and tongue coating samples were collected from each patient from each test period, the yeasts were counted by colony forming units per mL (CFU/ mL) and the species were identified. The patients were questioned about cleaner preference. An increase in the percentage of patients with no tongue coating after scraping was observed. A reduction in the mean number of Candida species in tongue coating was observed only after nylon soft-bristle toothbrush cleaner. Candida albicans was the prevalent species. Volunteers preferred to the steel tongue scraper (60%). Tongue cleaners reduced the tongue coating and the mean number of saliva's yeasts. Degree of tongue coating favors the Candida species colonization.

Do nobre ao patético: o herói de Victor Hugo e o anti-herói de Machado de Assis

This article analyses how Victor Hugo embodied his heroes and Machado de Assis his anti-heroes. Three Assis´s short stories and three Hugo´s novels are compared: “O caso da Vara” and the chapter “L‟affaire Champmathieu” from the book Les Misérables; “Noite de Almirante” and Les Travailleurs de la Mer; “Um incêndio” and Quatre-Vingt-Treize. These texts present similar situations, but each author shows an outcome that reveals their literary proposal. For this reason, Comparative Literature and Intertext had been used as base of reflection for this article.

Methods of Determining Porosity and Spatter Losses of Arc Welds

The original objective of this project was to determine the effect of varying current intensity and electrode coating composition upon the spatter losses and porosity of arc welds made by alternating current. This subject was suggested by the Welding Research Council of the Engineering Foundation, which is a clearing house for welding research in order to avoid du­plication of work.

Reflexión : punto de partida para la anti naturalización

Las cuestiones y doctrinas científicas estudiadas deben servir de instrumentos para el análisis y la reflexión, nunca constituir fines en sí mismos, ni doctrinas de salvación (no se adhiere a una teoría como a una religión). La lectura de Morgenthau o Aron, Rosencrance o Kaplan, Keohane o Kratochwill por citar algunos, debe permitir "ver" mejor, ya sea aspectos de la práctica científica, ya sean sus dimensiones éticas o políticas. Ello porque pasa de las cuestiones epistemológicas a las ético-políticas, y viceversa, casi sin solución de continuidad. El propósito de este artículo es reflexionar sobre ciertos supuestos que han naturalizado el conocimiento en las Relaciones Internacionales.

Reflexión : punto de partida para la anti naturalización

Las cuestiones y doctrinas científicas estudiadas deben servir de instrumentos para el análisis y la reflexión, nunca constituir fines en sí mismos, ni doctrinas de salvación (no se adhiere a una teoría como a una religión). La lectura de Morgenthau o Aron, Rosencrance o Kaplan, Keohane o Kratochwill por citar algunos, debe permitir "ver" mejor, ya sea aspectos de la práctica científica, ya sean sus dimensiones éticas o políticas. Ello porque pasa de las cuestiones epistemológicas a las ético-políticas, y viceversa, casi sin solución de continuidad. El propósito de este artículo es reflexionar sobre ciertos supuestos que han naturalizado el conocimiento en las Relaciones Internacionales.

Reflexión : punto de partida para la anti naturalización

Las cuestiones y doctrinas científicas estudiadas deben servir de instrumentos para el análisis y la reflexión, nunca constituir fines en sí mismos, ni doctrinas de salvación (no se adhiere a una teoría como a una religión). La lectura de Morgenthau o Aron, Rosencrance o Kaplan, Keohane o Kratochwill por citar algunos, debe permitir "ver" mejor, ya sea aspectos de la práctica científica, ya sean sus dimensiones éticas o políticas. Ello porque pasa de las cuestiones epistemológicas a las ético-políticas, y viceversa, casi sin solución de continuidad. El propósito de este artículo es reflexionar sobre ciertos supuestos que han naturalizado el conocimiento en las Relaciones Internacionales.

Improvements to the arc-spraying process

After a brief review of the various forms of thermal spraying equipment and processes, descriptions of the basic principles involved and the general functions for which thermally sprayed coatings are used are given. The background of the collaborating company, Metallisation, is described and their position in the overall market discussed, providing a backdrop against which the appropriateness of various project options might be judged. Current arc-spraying equipment is then examined, firstly in terms of the workings of their constituent parts and subsequently by examining the effects of changes in design and in operating parameters both upon equipment operation and the coatings produced. Published literature relating to these matters is reviewed. Literature relating to the production, comminution and propulsion of the particles which form the spray is discussed as are the mechanisms involved at impact with the substrate. Literature on the use of rockets for thermal spraying and induction heating as a process for feedstock melting are also reviewed. Three distinct options for further study are derived and preliminary tests and costings made to allow one option alone, the use of rocket acceleration, to go forward to the experimental phase. A suitable rocket burner was developed, tested and incorporated into an arc-spray system so that the sprayability of the whole could be assessed. Coatings were made using various parameters and these are compared with coatings produced by a standard system. Coatings were examined for macro and micro hardness, cohesive strength, porosity and by microstructural examination. The results indicate a high degree of similarity between the coatings produced by the standard system and the high velocity system. This was surprising in view of the very different atomising media and velocities. Possible causes for this similarity and the general behaviour of this new system and the standard system are discussed before the study reaches its conclusions in not proving the hypothesis that an increase in particle velocity would improve the mechanical properties of arc-sprayed steel coatings. KEY WORDS: Sprayed metal coatings, Electric arc spraying, High velocity flame spraying, Sprayed coating properties

Resistance of an epoxy coating with an organic inhibitor to cathodic disbondment in sea water

In this study, the effect of anti-corrosion inhibitor addition to epoxy coating, on the disbanding rate was evaluated. First to determination of mechanism, the bare steel substrates were immersed in the 3.5% NaCl solution and the solution containing 1 mM anti corrosion. The Electrochemical Impedance Spectroscopy was performed after 5 and 24 hour. The results indicated a lower corrosion rate in the presence of inhibitor. During the time, charge transfer resistance, was decreased for the substrates immersed in NaCl solution, and increased for the substrates immersed in NaCl solution containing 1 mM anti corrosion. This result can be related to more stability of corrosion products in presence of anti-corrosion and film formation. The coated substrates, with four different concentration of anticorrosion in coating, were protected under -1.2 voltage in the 3.5% NaCl solution. After 12 and 24 hour, the EIS test and disbanding area measurement, were evaluate. The lower disbanding rate, more charge transfer resistance and less double layer capacitance for the coating containing 0.75w% inhibitor, were observed. The result of Pull-off test after 1 day immersion in 3.5% NaCl solution, showed more wet adhesion for the coating containing 0.75w% inhibitor. The images of FE-SEM electron microscope and surface analyses EDX on the coated substrate after disbanding and the bare substrate immersed in 3.5w% NaCl containing 1 mM inhibitor, were proved the formation of stabilized film.

Design of functional hybrid coatings with anti-biofouling, self-cleaning and anti-reflecting applications

263 p.

In situ measurement of pipeline coating integrity and corrosion resistance losses under simulated mechanical strains and cathodic protection

A novel experimental assembly consisting of a specially designed tensile testing rig and a standard electrochemical flat cell has been designed for simulating buried high pressure pipeline environmental conditions in which a coating gets damaged and degrades under mechanical strain, and for studying the influence of mechanically induced damages such as the cracking of a coating on its anti-corrosion property. The experimental assembly is also capable of applying a cathodic protection (CP) potential simultaneously with the mechanical strain and environmental exposure. The influence of applied mechanical strain as well as extended exposure to the corrosive environment, coupled with the application of CP, has been investigated based on changes in electrochemical impedance spectroscopy (EIS). Preliminary results show that the amplitude of the coating impedance decreases with an increase in the applied strain level and the length of environmental exposure. The EIS characteristics and changes are found to correlate well with variations in coating cracking and degradation features observed on post-test samples using both optical microscopy and scanning electron microscopy. These results demonstrate that this new experimental method can be used to simulate and examine coating behaviour under the effects of complex high pressure pipeline mechanical, electrochemical and environmental conditions.

A comparative study of the structural, mechanical and tribological characteristics of TiSiC-Cr coatings prepared in CH4 and C2H2 reactive atmosphere by cathodic vacuum arc

TiSiC-Cr coatings, with Cr and Si as additional elements, were deposited on Si, C 45 and 316 L steel substrates via cathodic arc evaporation. Two series of coatings with thicknesses in the range of 3.6–3.9 μm were produced, using either CH4 or C2H2 as carbon containing gas. For each series, different coatings were prepared by varying the carbon rich gas flow rate between 90 and 130 sccm, while maintaining constant cathode currents (110 and 100 A at TiSi and Cr cathodes, respectively), substrate bias (–200 V) and substrate temperature (∼320 °C). The coatings were analyzed for their mechanical characteristics (hardness, adhesion) and tribological performance (friction, wear), along with their elemental and phase composition, chemical bonds, crystalline structure and cross-sectional morphology. The coatings were found to be formed with nano-scale composite structures consisting of carbide crystallites (grain size of 3.1–8.2 nm) and amorphous hydrogenated carbon. The experimental results showed significant differences between the two coating series, where the films formed from C2H2 exhibited markedly superior characteristics in terms of microstructure, morphology, hardness, friction behaviour and wear resistance. For the coatings prepared using CH4, the measured values of crystallite size, hardness, friction coefficient and wear rate were in the ranges of 7.2–8.2 nm, 26–30 GPa, 0.3–0.4 and 2.1–4.8 × 10−6 mm3 N−1 m−1, respectively, while for the coatings grown in C2H2, the values of these characteristics were found to be in the ranges of 3.1–3.7 nm, 41–45 GPa, 0.1–0.2 and 1.4–3.0 × 10−6 mm3 N−1 m−1, respectively. Among the investigated coatings, the one produced using C2H2 at the highest flow rate (130 sccm) exhibited the highest hardness (45.1 GPa), the lowest friction coefficient (0.10) and the best wear resistance (wear rate of 1.4 × 10−6 mm3 N−1 m−1).