Galvanic corrosion behaviour of electrodeposited Zn–Ni coatings coupled with steel

AbstractThe galvanic corrosion behaviour of detached electrodeposited Zn–Ni alloy coatings has been investigated during coupling with bare steel under two experimental conditions: total immersion in 600mM NaCl solution and exposure to neutral saltfog. Open circuit potential measurements made in NaCl solutions indicated that zinc alloys containing less tha approximately 14 wt-% nickel have potentials which remain negative with respect to steel over long immersion periods, suggesting that the coatings would behave sacrificially. This was confirmed by the galvanic current measurements which showed thatfor extended periods of time, zinc alloy coatings containing less than 14 wt-% nickel were sacrificial towards steel under both total immersion and salt fog conditions. Howeve,~ when the nickel level was increased above 14 wt-%, predominantly non-sacrificial corrosion behaviour was exhibited and steel corrosion was accelerated.