A study of the synthesis, characterization and properties of pulse-plated ultrafine-grained zinc-nickel alloy coatings.

摘要

In this thesis, the pulse plating technique was used to produce ultrafine-grained Zn-Ni alloy electrodeposits from a chloride-based electrolyte. The effects of the pulse plating variables (peak current density, on-time and off-time), some important bath conditions (ZnCl;The bath temperature had a very strong effect on the composition of the deposits which, in turn, had very strong effects on the phases present, surface morphology and grain size. The peak current density was found to have little effect on the composition and phases present, but had considerable effect on grain size. The on-time and off-time had no significant influence on the characteristics of the deposits, except for slight grain refinement observed with increasing off-time. The type of substrate material had little effect on the deposit characteristics. Only the ;The results of the neutral salt spray test (ASTM B-117) indicated that the corrosion resistance of Zn-Ni alloy coatings is superior to that of pure Zn and a commercial galvannealed coated steel and that the Zn-20wt% Ni as well as Zn-14wt% Ni alloys having the ;The microhardness of Zn-Ni alloy coatings was observed to increase with increasing Ni content. Several factors which contribute to the hardness such as solid solution hardening, effects due to different phases and grain size were discussed in order to explain the hardness behaviour.;Microcrystalline Zn-14wt% Ni alloy coatings were thermally stable up to a temperature of 200