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Wire & Cable ASIA – September/October 2007
88
March/April 2011
Abstract
It is increasingly difficult to deal with the contamination
of wastewater from zinc phosphate or zinc-calcium
phosphate coatings. This paper describes a conversion
coating process involving the electrolytic deposition of a
calcium phosphate carrier coat.
The process is efficient, free from heavy metals and
sludge, and well suited to wire drawing, cold heading and
extrusion.
The paper highlights the cost savings, environmental
benefits and productivity improvements that can be
achieved by a combination of calcium phosphating with a
polymer coating.
Synopsis
The lubricants currently used for drawing cold heading wire
and for cold extrusion processes are soaps.
In addition, molybdenum disulphide dispersions are
used for cold extrusion processes. These lubricants
are increasingly being replaced by ultra thin polymer
technology, which offers benefits such as improved tool
life, extension of the interval between oil changes in cold
heading machinery and allowing the fabrication of parts
with complex geometry.
These polymer coatings are applied on top of conventional
coatings as use on bare steel is restricted to a very few
specific cases.
Conventional coatings used are zinc phosphate or zinc-
calcium phosphate. However, it is becoming increasingly
difficult to deal with the sludge and heavy metal con-
tamination of wastewater from these processes.
The answer to these problems is given in this paper,
which describes a conversion coating based on the
electrolytic deposition of a calcium phosphate carrier
coating.
This process is highly efficient and free from heavy metals
and sludge. The conversion coating is eminently suitable
for wire drawing, cold heading and cold extrusion.
This paper highlights the cost savings, environmental
benefits and productivity improvements that can be
achieved by using a combination of calcium phosphating
with a polymer coating.
New technology for
lubricating cold extrusion
materials and cold
heading wire
By Jude Burke, Chemetall PLC, UK
Neutrali-
sation
Lubrica-
tion
Rinsing
Conversion
coating
Activation
Rinsing
Pickling
Figure 1
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❍
: State of the art workflow