One of the earliest patents on Zinc coated wires [US Patent
1896613-1933] directed towards improvement in the quality
of Zinc coated wires. In United States Patent No.
14,927-1979, it was disclosed that wire electrode coated with
a metal or alloy having a low vaporization temperature, such
as zinc, cadmium, tin, lead, antimony, bismuth and alloys
thereof, protecting the core of the wire against thermal shock
resulting from the occurrence of electrical discharges and
which permits to increase the frequency of the electrical
discharges without running the risk of rupturing the wire. US
Patent No. 4,968,867-90 discloses a wire electrode for wire
cut electrical discharge machining, which includes a core
wire having relatively high thermal conductivity, a lower
coating layer formed by a low-boiling point material (for
example, zinc) and an outermost layer of brass having high
mechanical strength. Here, the core wire is made of copper,
silver, aluminum or alloys. Certain effects such as Vibration
dumping effect, heat transfer effect, and resistance to
breakage were observed which ultimately increases the
machining speed. An EDM wire with a copper bearing core
and a substantially continuous coating of porous epsilon
phase brass, wherein said porous coating has been infiltrated
with graphite particles [US Patent No. 20070295695]. The
higher zinc content of the epsilon phase coatings has been
found to match the performance of beta phase coatings.
Therefore, the epsilon phase coating provides cutting
performance at par with beta or gamma phase coating, while
having a lower cost to manufacturer than either beta or
gamma phase.