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Long term outdoor exposure testing of various zinc-nickel plated products has indicated that better underfilm creep resistance is obtained when a nickel strike deposit is plated on the steel surface prior to plating the zinc-nickel alloy. These data are compared to other corrosion resistant coatings. Corrosion evaluation by short term Cyclic Corrosion or scab testing is also discussed. The adhesion of the various electroplated surfaces has also been investigated. It has been found that the presence of the nickel strike deposit improves the adhesion characteristic of this electroplated zinc-nickel alloy as demonstrated by the fact that the location of failure moves from an adhesive delamination of the electroplated alloy to a cohesive failure in the structural adhesive. The movement of the failure site appears to correlate with the improvement of the underfiim creep values in the Volvo test.

The results of scab corrosion tests conducted upon a painted commercial Ni-Zn alloy coating pretreated with various commercial phosphate chemical treatments are presented. The effect of these chemical treatments upon dry paint adhesion, blistering, and paint adhesion after water immersion (wet paint adhesion) is also shown. The results indicate that significant improvement in paint adhesion and a minimization of underfilm creepage can be effected by phosphate treating the nickel-zinc alloy surface with a zinc phosphate solution rich in manganese and nickel ions.