Performance of Zinc-Nickel Alloy Electrodeposits as Affected by Internal Stress

Zinc-nickel electrodeposited alloys prepared from alkaline and acid baths have been recognized for the excellent corrosion protection that they provide. For this reason these alloy deposits are included in a number of automotive specifications and are being used in a wide range of applications.

One issue with these deposits is that they have the ability to “micro-crack”. Investigations into this phenomenon have suggested that the internal stress of the deposit is an important factor in the formation, and subsequently, the prevention of these micro-cracks.

This paper describes the specifications for zinc-nickel alloy deposit to illustrate the performance expectations for automotive applications. The properties and characteristics of the alkaline and acid processes and the performance of the deposits are described. Then the measurement of, and characteristics of the internal stress are investigated.