V.K. William Grips

Investigation of surface composition of electrodeposited black chrome coatings by X-ray photoelectron spectroscopy

: Solar selective black chromium coating was electrodeposited on pre-treated electroformed nickel substrates from a hexavalent chromium containing bath. The composition of the film was investigated before and after annealing at 400 degreesC for different durations. In the as-deposited condition. the surface of the film was found to have trivalent chromium hydroxide and chromium in the chromate form contrary to previous studies which report the presence of hydroxides and metallic chromium. However in the present study, no evidence for metallic chromium was found. The major component. chromium hydroxide, was converted to Cr2O3 on annealing at 400 degreesC with the loss of water vapor. The chromate form remains but with a lowered concentration.

Electrodeposition of Ni and Co coatings from ionic liquid

Abstract The aim of the present study is to compare the structure and properties of nickel, cobalt and nickel–cobalt alloy coatings obtained from ionic liquid (IL) with those obtained from aqueous electrolyte. Choline chloride, a cheap and non-toxic IL, has been chosen for electrodeposition. The coatings obtained from IL displayed higher microhardness compared with those obtained from aqueous electrolyte. A difference in the surface morphology was observed. X-ray diffraction studies showed that the nickel rich coatings exhibited face centred cubic crystal structure, whereas those rich in cobalt displayed hexagonal close packed structure. Comparison in the corrosion behaviour of the coatings showed that the Ni coating possessed better corrosion resistance irrespective of the electrolyte adopted.

Preparation of Oil-Encapsulated Microcapsules and Tribological Property of Ni Composite Coating

Microcapsules containing oil are potential candidate materials for preparing electrocomposite coatings with excellent tribological properties. In the present study, the preparation of oil-encapsulated microcapsules and electrodeposition of Ni-microcapsule composite coating are presented along with the properties of the coating. In situ interfacial polymerization method was used for the preparation of lubricating oil-encapsulated urea-formaldehyde microcapsules. The synthesized microcapsules were incorporated into the nickel matrix by electrodeposition using Ni-Watts bath. The Ni-composite coating containing microcapsules exhibited smaller Ni grain size, higher microhardness and lower surface roughness compared to plain Ni coating. Electrodeposited Ni coating containing oil-encapsulated microcapsules exhibited improved tribological properties with lower wear loss and coefficient of friction compared to plain nickel coating.

The Corrosion Resistance of Nickel Electrocomposite Coating Containing BaFe12O19 Particles

Electroplating composite coating is an effective method to prepare composite coating through the codeposition of metallic, nonmetallic, or polymer particles with metal to improve properties such as corrosion resistance, hardness, and wear performance. This paper reports the synthesis of a novel Ni-BaFe12O19 magnetic nanocomposite coating exhibiting improved corrosion resistance. In the present paper, BaFe12O19 particles were synthesized by a single-step solution combustion method and characterized for phase, particle size, and morphology. These particles were incorporated in a nickel metal matrix, and the properties of the coatings like nanohardness and corrosion resistance were investigated. The coating microstructure was also studied using field emission scanning electron microscope. A Vickers hardness of 777 HV was exhibited by Ni-BaFe12O19, and plain Ni coating exhibited a hardness of 517 HV. The Ni-BaFe12O19 composite coating exhibited improved corrosion resistance compared to plain Ni coating with an value of 0.034 μA/cm2 compared to 0.361 μA/cm2 for plain Ni. The Ni-BaFe12O19 coating also exhibited higher charge transfer and polarization resistance compared to plain Ni coating.