Ultrafine polishing of nickel phosphorus plating with magnetic compound fluid slurry

Nickel phosphorus (Ni-P) plating on the optical lens mold is polished with magnetic compound fluid (MCF) slurry. Two types of MCF slurry are applied. MCF1 slurry is an HQ carbonyl-iron-particles (CIPs) BASF made and alumina abrasive particles based one while MCF2 slurry is a new zirconia-coated CIPs based one. The spiral shaped cutting marks on the Ni-P plating are eliminated by both the MCF slurries. As alumina abrasive particles in MCF1 slurry are a little larger and harder than zirconia abrasives in MCF2 slurry, scratches and CIPs embedding are caused and it is difficult to further improve the surface finish of Ni-P plating. In contrast, no scratches and CIPs embedding are induced with the new zirconia-coated CIPs based MCF2 slurry and improvement for the surface roughness of root mean square and Ra of the Ni-P plating is achieved. It is also found that polishing trace in both x-axis and y-axis directions is good to enhance the surface finish and the flatness of the Ni-P plating. The preliminary results show that MCF polishing is applicable for the nano-level polishing of soft magnetic material.