Electrodeposition of high phosphorus Ni-P alloys in emulsified supercritical CO₂ baths

The use of an emulsified supercritical CO₂ (sc-CO₂) bath for electrodeposition of Ni-P alloys was attempted. The material characteristics of the deposits with various P contents, formed by varying theelectrolyte composition and deposition current density, were investigated by means of scanning elec-tron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) for surface morphology and chemical composition and crystal structure analyses. The experimental results showed that the presence of sc-CO2in the electrodeposition bath could substantially improve the microhardness and the corrosion performance of the as-deposited Ni-P coatings. The roles of phosphorus and carbon in modifying the material properties of the deposits are discussed in detail.