21 Jul Brass: the antibacterial alloy
Hygiene and safety matter in relation to contact surfaces has always been an area to which particular attention should be paid, especially after the pandemic we have been facing over the last year. Microbes and bacteria can settle on surfaces and live for up to 30 days.
This is another reason why copper and its alloys – such as brass – are used in the manufacture of frequently touched objects (e.g. taps, handles and handrails) as materials with antibacterial and antimicrobial properties, although they are usually subjected to surface treatment.
Brass protects against harmful agents: scientific evidence
Data emerging from numerous studies (University of Southampton – UK) show that brass and copper alloys have a natural ability to remove harmful microorganisms relatively quickly (in many cases less than two hours!).
It was shown that at 20°C on copper (Cu 99.90%) and brass (CW617N) E. coli bacteria disappeared after 75 and 60 minutes respectively, whereas on AISI 304 steel (18Cr-8Ni) the bacterial population takes two days to decrease by 5 orders of magnitude, and then remains almost unchanged for the next 26 days. Polyethylene, in tests lasting 360 minutes, showed similar behaviour to steel.
One of the most famous experiments took place in 2008 at Selly Oak Hospital in Birmingham (UK), where the amount of bacteria located on the surfaces of frequently touched objects was measured. The objects used in the test were specially made for the experiment and did not present the surface treatment typical of commonly used copper and brass objects.
The obtained results speak for themselves: brass taps, tables and push plates for doors showed a 90-100% reduction in bacteria compared to similar objects made of “classic” materials such as plastic and aluminium, or externally chrome-plated objects such as taps.
Not even silver seems to own the virtuous properties of brass. In tests carried out at room temperature and humidity by Prof. Keevil of the University of Southampton, polyethylene coatings containing silver behaved like the steel control specimens, i.e. they showed no antibacterial properties.
How does brass manage to resist bacteria?
Brass and copper alloys were the first solid materials to be recognised by the Environmental Protection Agency (EPA) in 2008 for their antimicrobial properties.
Their antibacterial action is continuous over time, does not require additives to work and does not lose its effectiveness if the product is subjected to abrasion, even repeatedly; in addition, copper alloys work even if they oxidise naturally.
Copper, which is found in brass, is an essential nutrient for both humans and bacteria but, in high doses, copper ions can cause a number of negative events for the bacterial cell. The exact mechanism is not yet clear, but there are many theories about it. These include:
- loss of potassium or glutamate through the bacterial outer membrane;
- interference in the osmotic balance;
- binding to proteins that do not require copper ions.
A defence against Coronavirus
It is also worth highlighting the effectiveness of brass against Covid-19.
A study conducted in March 2020 showed that the virus can survive for two to three days on metal surfaces.
Hence the renewed interest in objects made of copper and its alloys, which can permanently kill the virus within 4 hours, making surfaces made of materials such as brass ideal for communal areas and all gathering places.
Moval brass machining: quality, reliability and safety
Thanks to their anti-bacterial properties, CW617N, CW724R or Ecobrass alloys are the perfect materials to develop products intended for the markets:
- Plumbing and heating;
- Construction and furniture;
- Chemical industry;
- Mechanical industry.
Moval is the ideal partner for performing extreme precision machining on brass, while preserving its mechanical and functional characteristics.
The high level of technical expertise, state-of-the-art machinery and a reliable and efficient production process enable us to produce durable, versatile and safe brass components.