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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

: State of the art workflow