Since lead is practically insoluble in copper, a cast copper-lead
microstructure consists of lead pockets in a copper matrix. These
pockets of lead serve as reservoirs for maintaining a continuous lead
film on the bearing surface.

With either continuous casting or powder-metallurgy techniques, a
steel backing is used with copper-lead bearings for increased strength.
These bearings are also frequently used with a babbitt overlay in a
three-layer construction. The hardness of copper-lead materials is
similar to that of babbitt at room temperature, but is higher at
temperatures approaching 300?. Corrosion of either the lead or copper
can be minimized by additives in high-quality automotive and industrial lubricating
oils.

Copper-lead systems are used for diesel engines on trucks and off-road
vehicles, although aluminum alloys are frequently specified for greater corrosion
resistance at a sacrifice of compatibility. Copper lead is
used in moderate load and speed applications, such as electric motors,
turbine engines, and generators.