The usual grade of copper used for engineering, architectural and plumbing applications is phosphorus-deoxidised copper. It has a minimum copper content of 99.9% with a small addition of phosphorus, which allows this grade of copper to be welded and brazed. Its thermal conductivity, corrosion, heat and UV light resistance, ease of joining, high ductility, malleability, toughness and 100% recyclability (two thirds of the copper ever mined is still in use today) make copper the standard material for these applications. Electrical grade copper also has a greater than 99.9% copper content and is readily available in many forms.
Swanepoel explains: "Copper is one of very few metals that has a particular colour, meaning it is not simply silver-grey. Bright copper is reddish-pink, whilst oxidised copper is dark brown. Additionally when exposed to the elements, copper undergoes a change in colour - known as patination - transitioning from a reddish-pink to a blue-green."
"No metal is more suited to alloying than copper, a practice dating back to the beginning of civilisation, but still very much in use in many modern-day applications. Formed by mixing various compositions of metals in the molten state, alloys are used to expand properties for specific end uses. Alloys of copper give designers and architects further choices in terms of application and colour," continues Swanepoel.
Brasses are alloys of copper and zinc, and have a variety of attractive colours, ranging from red and yellow to gold and silver. With the addition of one percent manganese, brass will patinate to a chocolate-brown colour. Nickel silvers may be considered to be special brasses, and although they contain no silver content they resemble silver in appearance. Tin and phosphor bronzes are reddish-brown in colour; whilst aluminium bronzes have an attractive golden colour, which will darken slightly over time. Depending upon the copper content of copper-nickels, the colour of these alloys ranges from slightly pink-silver, to completely silver in colour, resembling the appearance of stainless steel.
With over 450 approved alloys to choose from, offering a wide range of properties and attributes, it is easy to select an appropriate alloy for the application and fabrication route required. In fact, there will usually be several that meet particular design and architectural requirements. Today, copper and copper alloys are available in sheets, meshes and expanded metal, which give an air of transparency.
Swanepoel explains: "The majority of us take for granted the lighting, heating, communications, running water, domestic appliances and entertainment systems in today's homes. All of these are reliant on copper components. In addition, copper and brass are widely used in both utility and decorative items such as cookware, door fittings and furniture. Copper also supports renewable energy and plays an essential role in the solar thermal heating and cooling systems, wind turbines and photovoltaic panels that are increasingly incorporated into 21st century homes."
Copper plumbing systems ensure the long-lasting, trouble-free and safe delivery of water for drinking, washing and heating. They are used in buildings of all types, from hotels and offices, to private houses and apartments. These buildings also remain secure thanks to locks and keys made from copper alloy components that ensure reliability, strength and freedom from corrosion.
Its excellent durability means that a copper component can often outlive the product or application of which it is a part. In buildings, copper cladding, a copper roof or copper guttering and downpipes can last for hundreds of years. Over time, copper used in outdoor applications will weather and oxidise and take on its familiar green patina. Manufacturers also now have factory methods that can apply oxidised or patinated surfaces straight away.
Science has demonstrated the naturally antimicrobial properties of copper in the fight against potentially life-threatening infections. Bacteria and viruses, including those from the influenza family such as H5N1 (bird flu) and H1N1 (swine flu), are rapidly inactivated on contact with copper. This inherent property has seen the use of antimicrobial copper surfaces dramatically increase in hospitals and food preparation areas. Copper piping also helps limit the spread of Legionnaires' disease, as well as combating gastro-intestinal infections by reducing the risk of water being contaminated by the Escherichia coli or Listeria bacteria.
With its pores and sweat glands, human skin might be one of world's best natural air conditioners. Biologist turned architect, Doris Kim Sung, proposed in her TED talk last October that building skins should be more similar to human skin. Considering that 30-40% of all primary energy consumed worldwide goes toward heating and cooling buildings, Sung's sustainable design concept could be a more passive method for ventilating buildings. The material she has in mind is a thermo-bimetal strip - two thin pieces of copper and steel sandwiched together. These two metals expand and contract when heated and cooled. When it is hot the metal bends one way, conversely when it is cold, it bends the other. This means that when direct sunlight hits the bimetal strips, they would bend inwards and close together to shade the building, then when the building gets too hot, the metal could bend in such way that opens up "pores" to release heat.
"It is unlikely that we will get to the point where we can truly be rid of air conditioning, especially in certain parts of the world, but this application would reduce the amount of air conditioning or heating used just by making buildings more cleverly designed," concludes Swanepoel.
For more information, go to www.copperalliance.org.za.
