1,721,056 research outputs found
Electrochemical Deposition of Composite Coatings
No full textMetal matrix composite coatings are widely used to cover metallic components. It is a relatively cheap solution to enhance the resistance of metallic parts to aggressive working conditions and to increase the component service life. Electrolytic codeposition is used to produce composite coatings by embedding particles, intentionally added to the plating bath, into a metal matrix in the course of an electrolytic deposition process. Following a brief overview of the history of electrochemical deposition of composite coatings, the principles of the codeposition process are considered, and then, mainly accepted mechanisms are reported. The main categories of composite coatings obtained by electrodeposition are briefly described, and the influence of the process parameters to the composition and structure of the obtained composite deposits are illustrated using examples
e-MINDS: electrochemical processing methodologies and corrosion protection for device and systems miniaturisation–first year of a successful COST action
No full textEffect of ultrasound vibration during electrodeposition of Ni-SiC nanocomposite coatings
No full textThe deposition of pure Ni and Ni/SiC nanocomposite coatings was carried out using an additive free Watts type bath. In order to avoid porosity and defects induced by the hydrogen evolution ultrasonic vibration was used during the electrodeposition. The effects of the ultrasound treatment on both pure Ni and Ni/SiC nanocomposite codeposition was investigated by means of coatings microstructure and surface morphology study and SiC content measurements. Moreover, it was demonstrated that the ultrasonic vibration reduced the layer porosity. The role of ultrasounds in reducing porosity was shown
Influence of the particle size on the mechanical and electrochemical behaviour of micro- and nano-nickel matrix composite coatings
No full textThe aim of this work is the production and characterization of composite nickel matrix electrodeposits. Pure nickel and composite nickel matrix deposits containing either micro- or nano-particles of silicon carbide were prepared using a Watts type bath. The electrodeposition was carried out under both direct and pulse current conditions at different frequencies. With the same quantity of powder in the bath, the embedded micro-powder content is about 25-30%w while the nano-powder content is always less than 1%w. The mechanical properties of the nano-composites increases despite the low ceramic content. SEM micrographs of the microstructure and XRD-line profile analysis show that the presence of ceramic powder in both baths changes the crystallisation process leading to enhanced mechanical properties even at ceramic contents less than 1%, as in the nano-composite case. The presence of the ceramic phase and changes in the microstructure both decrease the mass loss during abrasion by up to 70% for micro-composites and 45% for nano-composites
Corrosion resistance in different environments of Ni Matrix Micro- and nano-composite electrodeposits
No full textThe galvanic codeposition of ceramic particles for the production of metal matrix composite coatings is a research domain of wide interest as these deposits could be used for a large field of applications, especially in cases where high wear and corrosion resistance are required. The aim of this work is the production and characterization of nickel matrix micro- and nano-composite deposits. Three types of deposits have been produced: pure Ni deposits, Ni containing SiC microparticles and Ni containing SiC nanoparticles. A Ni sulfamate electroplating bath containing the particles in suspension has been used and the deposition was carried out using both direct and pulse current at different frequencies. ASTM 387 gr.22 steel plates were used as substrate. The microstructure of the obtained deposits has been observed by Scanning Electron Microscope at both top surface and cross section after metallographic etching. The SiC content along the whole thickness of the deposits has been evaluated by Glow Discharge Optical Emission Spectroscopy. The corrosion resistance of the coatings has been evaluated by potentiodynamic polarization curves in two different corrosive environments: a solution containing 3.5% NaCI, and a solution containing H2S and NaCI at 50°C. The degradation mechanisms have been evaluated by SEM observation of the corroded samples on both top surface and cross section. The codeposition on SiC micro-particles decreased the protective properties of the coatings while the codeposition of nano-particles did not penalize the high corrosion resistance of the nickel coatings in the above mentioned corrosive environments. The microstructural modifications induced by the codeposition of the particles influence the degradation mechanisms
The Use of the Electrochemical Micro-cell to Study Corrosion Inhibition by Cerium Species on AA1050 Aluminium Alloy
No full textScaling-up of the electrodeposition process of nano-composite coating for corrosion and wear protection
No full textThe codeposition of hard nanoparticles into metal matrix electrodeposits usually leads to the increase of the coating hardness and abrasion resistance and causes a change to the microstructure of the deposits leading to more compact, nanostructured coatings with an increased corrosion resistance. Very often the laboratory scale results are not easily transferable to an industrial scale due to the introduction of new process variables such as the geometry and the dimensions of the component to coat. The aim of the present work was the study, in laboratory scale, of nano-composite nickel matrix coatings containing SiC nanoparticles and the transfer of this technology in industrial scale. The deposits have been produced using a Watts type bath containing 20 g/l of nanoparticles, under galvanostatic conditions using a current density of 2 A/dm2. The deposits have been studied regarding their microstructure, abrasion and corrosion resistance. Based on the satisfactory results of the laboratory tests, the second part of this work contains the scaling-up and the industrialization of the process and the electrodeposition of the composite coating on ship propeller models and profiles as well as on train axles. The prototype parts were tested under actual working conditions
Study of the synergistic effect of cerium acetate and sodium sulphate on the corrosion inhibition of AA2024-T3
No full textThis study presents a detailed characterisation of the AA2024-T3 immersed in
NaCl+Ce(OAc)3 solutions without and with added Na2SO4 at various concentrations aimed to
understandthe synergistic effect of cerium and sulphate ions on corrosion inhibition.
The corrosion process was evaluated using micro- and macro-scale electrochemical
techniques performing anodic polarisation and electrochemical impedance spectroscopy
measurements. The cerium species on alloy surface were analysed using a scanning electron
microscope coupled with energy dispersive X-ray spectroscopy as well as atomic force and
scanning Kelvin probe force microscopy.
The results show a corrosion inhibition of AA2024-T3 immersed in NaCl+Ce(OAc)3,
which becomes more effective in the presence of Na2SO4 due to a synergistic effect between
ions involved in the inhibition process. The local techniques confirm the formation of insoluble
cerium species on intermetallics and on aluminium matrix. The synergistic effect results in the
formation of more compact and more durable film, which significantly retards the corrosion
process
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