Zinc-nickel Alloy Plating Process And Performance

Zinc-Nickel alloys are a kind of new and protective coatings and have been developed for recent ten years. This alloys have a promising future because of their high corrosion resistance, low hydrogenous brittleness, facile jointing and good mechanical properties. In this paper, electroplating Zinc-Nickel alloys has been realized by selecting appropriate anode and mode of controlling anode current and adopting new additive and complexant. The new process conditions and solutions of electroplating Zinc-Nickel alloys have been obtained and researched from all aspects. The research of cathodic current density, pH, temperature, and the rule of every components of electroplating solution effecting the content of nickel has been put on the emphasis. The passivation of Zinc-Nickel alloys has been made from adopting new passivation solutions and good process. The metabolic rule of Zinc-Nickel alloy coatings components, microcosmic appearance and structure, corrosion production and the structure of passivation film and components have been analyzed and researched by means of adopting XRD, Glow Discharge Optical Emission Spectrometry (GDA-750), SEM(HitachiS-570) and Multifuctional Electronic Energy Spectrum(ESCALAB MK- II). The property of the Zinc-Nickel alloys corrosion resistance has been researched by the electrochemistry test and the neutral salt spray test. The results show: (1) By the new process conditions and solutions of electroplating , the Zinc-Nickel alloys which the content of nickel is in 9 at% to 12 at% , has good appearance and high corrosion resistance has been obtained. (2) When the thickness of Zinc-Nickel alloys coatings increase, the content of zinc increase, but the content of nickel increase at the first some times and then decrease. There is an enrichment of nickel in the coatings. (3) Zinc-Nickel alloys electrodeposits exhibit different alloy phases as a function of their alloy composition. When the content of nickel is under 6at%, alloys have n -phrase which is a solid solution of nickel in zinc. When the content of nickel is 6at%~9at%, there is dispersion r -phrase. Alloys of 10~ 14% nickel are Y -phrase mainly. When the content of nickel exceeds 25at%, ally have a -phrase mainly and have little -phrase.(4) The stabilized potential of alloys that the content of nickel is under 14% increase when the content of nickel increased. The properties of corrosion resistance of passivation Zinc-Nickel alloys are much more than the properties of passivation zinc coatings, passivation cadmium coatings and alloys of cadmium-titanium. (5) The corrosion productions are mainly ZnO and ZnCl2 4Zn(OH)2, have little 2ZnCO3 3Zn(OH)2 and isn't nickel. (6) The passivation films of Zinc-Nickel alloy are mainly made up of CrO3 Na2CrO4 and H2O and there is a enrichment of nickel between the passivation films and alloy coatings. When the passivation temperature increase , the thickness of passivation films increase .