COMPOSITIONALLY MODULATED ZINC ALLOY COATINGS FOR CORROSION PROTECTION

An investigation has been undertaken to attempt to electrodeposit laye red coatings of zinc. nickel and zinc-nickel alloy. A dual electrolyte approach has been applied with sequential layers being electrodeposit ed from the two baths. Coated steel substrates have been sectioned and examined using scanning electron microscopy and the layered nature of the deposits confirmed. Electrochemical and salt fog corrosion tests have been undertaken to ascertain the corrosion protection capabilitie s of various layered coatings. Preliminary data. particularly from the salt fog trials. suggests that some of the layered structures have co nsiderably better protective qualities than similar thickness coatings of zinc and zinc-nickel alloy.