A relatively recently developed group of zinc-aluminum alloys are making significant inroads against traditional materials such as bronze for plain bearing and bushing applications.

A family of three primary alloys -- ZA-8, ZA-12 and ZA-27 -- were developed and aimed at the need for high performance, high quality, zinc alloys for die casting and gravity casting.

But ZA-12, considered the middle-of-the-road, general purpose alloy, has also broken out and found a niche for itself as a material preferable to bronze for heavy-duty plain bearings, journal bearings and bushings. It is generally best suited to high load, low speed applications.

The ZA-12 nomenclature means it is a zinc alloy with 12% aluminum, along with copper and magnesium. The copper and magnesium add dimensional stability and castability. Up against bronze, aluminum or brass, zinc alloys are also higher strength and less expensive. They can be left as-is, painted, plated or anodized. ZA-12 has approximately the same density as cast iron.

Because of the alloy makeup, ZA-12 and below (ZA-3,-5,-7,-8) are also classified as nonsparking, making them inherently preferable for use in flammable gas environments, mining and forestry equipment applications. They are also nonmagnetic, suitable for sensitive electronics and electronic fabrication equipment.

As a bearing material, the zinc alloys have a number of advantages such as relatively low melting points. But ZA-12 in particular has more bearing-friendly qualities such as high machinability, inherent lubricity, stability, high wear resistance, strength, durability, corrosion resistance and resistance to galling.