CORROSION RESISTANCE OF ELECTROPLATING ZINC-NICKEL ALLOY

The corrosion resistance of a zinc-nickel alloy had been studied by electrochemical testing and neutral salt spray testing.The coating components,microcosmic appearance,structure and corrosion products of zinc-nickel alloy had been analyzed by means of XRD,Glow Discharge Optical Emission Spectrometry and SEM.When the thickness of zinc-nickel alloy coatings increased,the content of zinc increased,but the content of nickel increased at first and then decreased.There was enrichment of nickel in the coating.Zinc-nickel alloy electrodeposit exhibited different phases as a function of their alloy composition.When the content of nickel was less then 5%,the alloy was composed maily of η-phrase which is a solid solution of nickel in zinc.When the content of nickel exceeded 79%,the alloy was composed maily of α-phrase.In other ranges,zinc-nickel alloy exhibited sophisticated phases.The corrosion resistance of passivated zinc-nickel alloy was much more better than that of passivated zinc coatings,passivated cadmium coatings and alloys of cadmium-titanium.The corrosion products were mainly ZnO and ZnCl2·4Zn(OH)2,with little 2ZnCO3·3Zn(OH)2.