Copper recycling and sustainability Back Ford
Page 8
Brass and recycling
 

The brass industry throughout the world depends on the recycling of brass scrap for its survival. Making brass from new copper and zinc would be uneconomical and wasteful of raw materials so, since new brass articles are made from recycled scrap, brass is said to be sustainable. In the UK brass manufacturers use almost 100% brass scrap.

Recyclability of brass
Whether it is from production scrap (as shown) or end of life brass products, brass can be recycled over and over to make new products such as taps, fasteners and handles

Applications
Gold coloured brass objects are abundant in everyday use; they include;

  • screws and pins
  • door bolts and locks
  • door handles
  • coat hooks
  • hand rails
  • buttons
  • zip fasteners
  • ornaments
  • light fittings
  • garden taps and hose fittings
Sometimes brass is plated with chromium as in bathroom and kitchen taps; the appearance then is silvery and shiny.

Brass in a vital safety role
A brass component which is hidden from view, but which plays a vital safety role in vehicles, is located in seat belt fittings. This is a 'standing man', made by Securon which topples over and locks the seat belt when rapid deceleration associated with an accident is experienced, keeping the passengers safely secured. Brass was selected for this component because of its ease of machinability and good corrosion resistance. Its density allowed a small compact component to be designed which fitted into the seat belt housing.

Alloys
Brass is not just one composition; brasses consist of alloys of copper with zinc ranging from 5 to 40%. In addition small amounts (less than 5% each) of alloying elements are added to give the improved properties indicated:

  • Lead - for better machinability (brass has the best machinability of any metal)
  • Aluminium - to improve corrosion resistance
  • Manganese, iron, tin, aluminium - for improved strength

Colours of brass
Brasses have a range of attractive colours ranging from red to yellow to gold to silver. With the addition of 1% manganese, brass will weather to a chocolate brown colour. A type of brass called nickel silver (no silver but 18% nickel) will polish to a brilliant silver colour. Brasses are easy to shape, and with all these colours available it is not surprising that architects and designers have used brasses to enhance the appearance of new and refurbished buildings, both inside and out.

Brass applications

Applications which enhance the appearance of houses include:

These objects are both beautiful and functional.

Properties
As well as attractive colours and easy shaping, brasses have other useful properties such as:

  • High electrical conductivity, wear resistance and corrosion resistance - these properties are required in the pins of a 13 amp plug
  • High thermal conductivity - where heat has to be removed efficiently brass is an excellent choice due to its high thermal conductivity - it finds use in car radiators for this purpose.
  • High strength - important for door lock parts which have to resist bending.
Antimicrobial copper applications
Brass door handles and push plates being fitted in a medical ward in a clinical trial to assess copper's role in combating hospital-acquired infections.

Brass and hygiene
You will all be aware from TV, press and perhaps the experience of relatives of the fight against hospital acquired infections such as MRSA (Meticillin Resistant Staphylococcus aureus) and C. diff (Clostridium difficile), which in some cases are fatal.

It has been shown that these pathogens, which can be spread by touch, will die in a few hours on copper/brass surfaces. This does not happen on stainless steel or plastic.

As a result of this antimicrobial action, copper/copper alloys such as brass are being evaluated in hospitals in high-touch applications such as doorknobs, grab rails, push plates, fittings, pens and work surfaces.

These hospital trials will evaluate the role that copper and copper alloy products could have in combating these harmful bacteria.

This social aspect of the action of copper/brass is an example of the sustainable nature of these alloys.

Sources of brass scrap
All of the objects mentioned above will at the end of their useful life be available for recycling; they are too valuable to be thrown away and end up in landfill. Hence you could play a part when, after any home refurbishments, taps, locks, pipes, letter boxes or ornaments are being discarded, by ensuring that these things are recycled by taking them to your local authority recycling centre. In the factories where brass is made there is a very well organised system of recycling waste that arises from the manufacturing process. In addition clean scrap of known composition may be bought in.

Questions
1. The zinc content of brass ranges from %

2. Which element gives brass its good machinability?

3. What colours are available in brass?

4. Which elements give brass extra strength?

5. In which of the following is the electrical conductivity of brass important?

6. The recycling of discarded brass enables new brass to be produced economically. This is an example of the of brass.

7. Copper is naturally antimicrobial against a range of organisms - viruses, fungi, moulds and bacteria. Which of the following infections are caused by bacteria?

back top next