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RECYCLING
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Zinc is the principal raw material in galvanizing.
Zinc is an inherently recyclable non-ferrous metal. It can be recycled
indefinitely without any loss of physical or chemical properties. This
is a major advantage for the hot dip galvanizing process ensuring its
environmental sustainability and its cost effectiveness.
About 30% (3 million tonnes) of the world's zinc consumption is from
recycled sources. A figure which is increasing with increased
environmental awareness and improvements in recycling technology.
Estimates suggest that 80% of zinc available for recycling is in fact
recycled. This means that much of the zinc in use today has probably
been used before.
For example, the car you drive contains up to 10 kg of recycled zinc in
its galvanized body panels and when it is discarded these panels can be
readily made into new parts of identical quality. Even the zinc oxide
used to cure your tyres is recoverable to make new tyres.
The table below illustrates how galvanizing is an important source of recycled zinc:
|
Brass scrap |
42 |
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Galvanizing |
27 |
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Die casting scrap |
16 |
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Steel industry filter dust |
6 |
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Zinc roof sheet/semi-products |
6 |
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Chemical industry |
2 |
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Other |
1 |
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100% |
source: International Zinc Association
RECYCLING OF GALVANIZED PRODUCTS
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The presence of a zinc coating on steel does not restrict its
recyclability. Galvanized steel is recycled with other steel scrap in
the steel production process; it volatilises early in the process and
is collected for reprocessing.
OTHER EXAMPLES OF USES AND MARKETS FOR RECYCLING
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- Zinc oxides - pharmaceuticals, food, fertilisers and for curing rubber.
- Zinc dust - paints, chemicals, lubricants, batteries and in gold recovery.
- Alloyed with other metals - cast into precision parts for appliances, hardware, electronics and toys.
Zinc recycling circuit
RECYCLING AND THE GALVANIZING PROCESS
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Hot dip galvanizing is very efficient in its use of zinc, as any
of the molten metal not forming a coating on the steel will run back
into the galvanizing bath.
Three residual products are formed during the process; a zinc/iron mix
called dross, zinc ash and flux-skimmings. All of these contain
valuable zinc and are recovered and recycled by specialist firms and
the recycled zinc is often returned to the galvanizer. Zinc oxide is
recovered from galvanizers' ashes and used in pharmaceutical/beauty
products and tyre manufacture.
PUMP ROOMS
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Tenbury Wells, Worcestershire
The restoration of this unusual building showed that the galvanized
steel cladding and roof sheets, which have protected the building for
nearly ninety years, can, at the end of their life be re-galvanized to
provide the same protection all over again.
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