Application Of Metallic Coatings Research Articles

Quality assessment of zinc coatings applied by selected methods

Purpose: This article presents the problem of corrosion phenomena occurring on steel products, which contributes significantly to the shortening of safe service life. One method of corrosion protection is the application of metal coatings. The most commonly used zinc coatings are described, along with two methods of their application: the galvanizing bath method and the lamellar method. Design/methodology/approach: Coatings were made on the S195 steel specimens in different process variations. Weight, hardness and thickness, as well as surface defects, were used as criteria for assessing the quality of the coatings. Findings: It was found that the process in the galvanizing bath can produce untight coatings with defects. On the other hand, the coatings applied by the lamellar method, were characterized by better aesthetics, lower weight and thickness compared to galvanic coatings, higher hardness compared to galvanic coatings, and uniformly covered the material without discontinuities in the structure that could impair durability. Originality/value: The research clearly indicated the directions of application of the analyzed galvanic and lamellar coatings. The application of coatings is justified in the use of products exposed to corrosive agents. In terms of decorative qualities, more favourable results were obtained on the specimens with lamellar coatings, as these coatings had a silvery colour and an aesthetically pleasing sheen compared to the galvanic coatings. Due to the characteristics of the coatings, galvanic coatings can be used on parts that are operated in harsh environments, while lamellar coatings can be recommended for products that are required to have a low weight change and certain aesthetics Keywords: galvanizing, galvanic coatings, lamellar coatings, coatings quality. Category of the paper: research paper.

Review of modern methods of presurface preparation of aluminum alloys for metal coating (part 2)

Here is an overview and comparative characteristics of modern methods of surface preparation of various grades of aluminum alloys for the application of metal coatings. Moreover, some types of preparation can be used for direct metal deposition. Particular attention is paid to technologies for creating an oxide film as a basis for electroplating.

Review of modern methods of presurface preparation of aluminum alloys for metal coating (part 1)

Here is an overview and comparative characteristics of modern methods of surface preparation of various grades of aluminum alloys for the application of metal coatings. Moreover, some types of preparation can be used for direct metal deposition. Particular attention is paid to technologies for creating an oxide film as a basis for electroplating.

Metallic coating technologies for carbon fabrics and methods for assessing their quality

The results of experimental analyses of the properties of carbon tapes (and filaments) after the application of metal coatings on them are presented. Various methods have been investigated for pre-cleaning the surface of carbon tapes and fabrics before applying a metallic coating thereon. A magnetron sputtering method was used to apply the metallic coating. An algorithm has been developed that allows determining the method of pre-cleaning carbon tape before its metallization. An adhesive test method was used as a criterion, allowing to determine the adhesion strength of the metallic coating to the carbon tape. An algorithm has been developed that allows determining the modes of applying metallic coatings on a carbon tape. Modes of applying metallic coatings on carbon tapes have been developed.

Development of Fe-Ni-W alloys for steel parts coverings

The metallic coatings have their importance in the protection of structures against corrosion, gaining relevance as they bring financial benefits to avoid contamination, loss of efficiency, accidents, among other undesirable and costly situations. Electrodeposition is a mechanism used for the application of metallic coatings, and has been widely used industrially for Chromium alloys, which end up being harmful to the environment because of its carcinogenic nature. Thus, this work has as main objective to develop corrosion-resistant Fe-Ni-W alloys, evaluating process parameters such as electrical current density, cathodic rotation and electrolytic bath temperature. The study of the influence of these parameters on the electrodeposition of Fe-Ni-W contemplated the efficiency and rate of deposition. The electrodeposition tests were carried out on previously treated carbon steel substrates, using electrolytic baths with pH adjusted according to a metal speciation study and the application of electric current with the aid of a potentiostat. Fe-Ni-W alloys were characterized by Scanning Electron Microscopy (MEV) with X-ray Dispersive Energy Detector (EDS). The maximum deposition efficiency achieved was 50%. The compositions of Iron and Nickel in the alloy were influenced by variations in temperature and cathodic rotation, with the percentage of Iron being around 40% when using the temperature of 25 oC and the rotation of 15 rpm.

Diffusion Analyses Using GDOES Technique of the 22MnB5 Press Hardened Steel with Al-Si and Zn-Ni Coatings

The hot stamping process consists to heat the steel blank, at total austenitization temperatures and to transfer it into the press tooling for forming and fast cooling to fully martensitic transformation. This transference from furnace to press stage promotes some steel oxidation. The application of metallic coatings avoids this phenomenon. The Al-Si coating, a patented process, has been the most applied on steel. Hence, alternative coatings like Zn-Ni are under development. It is known that this furnace heating causes chemical elements diffusion that results in intermetallics formation. This study had the objective of analyze the diffusion profiles of chemical elements present in the substrate, 22MnB5 steel, and coatings of Al-Si and Zn-Ni, using glow-discharge optical emission spectroscopy - GDOES and to correlate the results with those obtained with energy dispersive X-ray spectroscopy - EDS. The results showed that for the Zn-Ni sample, the Zn and Fe profiles at the interfacial zone, are predominant; which justify the high proportion of ZnFe phases as showed using scanning electron microscopy - SEM images. For the Al-Si sample at the interfacial zone, the profile of Al and Fe varies simultaneously; besides that, silicon diffusion in the substrate is more effectively than the nickel diffusion. For this reason, it was possible to identify AlFeSi phase near to the steel substrate.

Avaliação do campo de tensões residuais por difração de raios - X utilizando o método do sen²ψ em revestimentos metálicos do aço inoxidável E308-L

A aplicação por soldagem de revestimentos metálicos de aços e ligas nobres resistentes à corrosão é uma alternativa bastante razoável economicamente frente à fabricação de componentes maciços nestas ligas. Entretanto há uma carência de informações sobre as alterações mecânico/metalúrgicas causadas pelos ciclos térmicos de soldagem quando da aplicação destes revestimentos, principalmente sobre a influência sobre o nível de tensões residuais , que é mister no entendimento do fenômeno da corrosão assistida por tensão. O objetivo deste trabalho foi avaliar o nível de tensões residuais superficiais em revestimentos do aço inoxidável AWS E308-L T-1 aplicados pelo processo de soldagem ao Arco Elétrico com Arame Tubular sobre chapas do aço ASTM A36. As medições das tensões residuais foram realizadas por um difratômetro portátil de raios - X na superfície dos revestimentos e os principais resultados obtidos foram que a natureza das tensões residuais na superfície dos revestimentos sempre se apresentou compressivas e não observou-se uma linearidade da magnitude das tensões residuais em função da energia de soldagem.

Rethinking Casein Micelle Structure Using Electron Microscopy

Numerous models for the structure of casein micelles have been proposed in the past. Based on the chemical and physical properties of micelles, these models fall into two general categories, models of internal structure and models of submicelles. Electron microscopy has been used to provide evidence for these models, although the available techniques imposed limits. With the development of newer electron microscopes, the structure of the bovine casein micelle has been further examined. Even at high resolution, scanning electron microscopy does not produce satisfactory images of casein micelles because the application of metal coatings (2 to 10nm thickness) obscures the proteins from view, and the resultant images of casein micelles resemble a lumpy sphere. Transmission electron microscopy has been used with varying results. Freeze-fracture replica methods coat the fine protein structure with metal, as occurs with scanning electron microscopy. Negative staining that includes air-drying introduces artifacts into the sample during drying. Plastic embedding can yield fairly representative images, but not without dimensional compression and some chemical modification. These chemical modifications occur predominantly from 1) chemical fixation, causing crosslinking of protein and thus shifting of their spatial resolution; 2) ethanol, causing coagulation of the proteins during dehydration; and 3) protein loss during infiltration with plastic. The inability to avoid these problems in the past has limited the ability to provide an accurate image of casein micelles. In this study, a cryopreparation technique has been applied to examine single casein micelles while retaining the maximum in situ structure. To avoid problems of metal coating and chemical modifications, casein micelles were absorbed to parlodion-coated grids, immersed in uranyl oxalate counterstain, quick frozen, and freeze-dried. This method yields images of whole, spherical casein micelles and shows the fine structural detail of the micellar proteins. Stereo images showed that the largest subaggregate particles within the casein micelle matrix were approximately 8 to 10nm in size.

Application of metallic coatings to powders by the vacuum deposition method (review)

Application of metallic coatings to powders by the vacuum deposition method (review)

1791. Application of metallic coatings on welded parts of titanium and its alloys: A G Atanasiants et al, Protection of Metals, 1, 1965, 203–204 (in Russian)

1791. Application of metallic coatings on welded parts of titanium and its alloys: A G Atanasiants et al, Protection of Metals, 1, 1965, 203–204 (in Russian)

Friction and wear properties of titanium

All of the lubricants evaluated, with the possible exception of fluorocarbons, are ineffective in reducing the galling of bare titanium metal. However, many of the wear problems have been minimized by coating the surface of the metal and then lubricating this surface. Thus, the wear resistance of the metal can be improved by oxide, nitride, and carbide case hardening and coatings. Chemical conversion coatings such as fluoride, phosphate, and anodized coatings help retain the lubricant and improve the resistance to galling. The most satisfactory procedure for preparing titanium surfaces for severe service is by the application of metallic coatings. Of the coatings tested, nickel has given the best results to date.