Masayuki Yokoi

Electrodeposition of NiP alloys from Ni-citrate bath

Abstract In the electrodeposition of NiP alloy from a Ni-citrate bath, changes in P content and current efficiency of NiP deposits with plating variables such as H2PHO3 concentration, current density, bath pH and temperature were investigated. P content of the deposits was found to be constant around 25 at.% in a wide range of plating conditions. It was concluded that NiP alloy electrodeposition is controlled by Ni deposition rate and by the strong interaction between P and Ni, and that NiP alloy is formed through a direct deposition mechanism.

Corrosion Resistance of Cr-P-C Alloy Plating Film Produced Using a Trivalent Chromium Bath

Corrosion rates of Cr-P-C alloy plating film produced using a trivalent chromium bath were measured in hydrochloric acid, hydrofluoric acid, aqua regia, sulfuric acid, nitric acid and sodium hydroxide solutions by a weighting method, and compared with those of conventional Cr plating film produced using a hexavalent chromium bath. And corrosion behavior of both films in a hydrochloric acid solution were studied using electrochemical polarization measurements and XPS analysis. Cr-P-C alloy plating film was found to have an extremely high corrosion resistance even in hydrochloric acid, hydrofluoric acid and an aqua regia solution, while the conventional chromium film dissolved completely in those solutions. XPS studies revealed that Cr-P-C alloy plating film was covered by a chromium oxide layer on top of the film surface. Metallic phosphorus concentrated under the oxide layer, which protects the alloy from corrosion in a hydrochloric acid solution.