News in Science

'Poisoned' alloy the metal of the future

Future metal Cars, planes and portable devices could be much lighter in the near future thanks to a newly developed metal alloy that is laced with a touch of poison.

An international team of scientists, led by Associate Professor Nick Birbilis of Monash University in Melbourne, have found adding small amounts of arsenic, dramatically reduces rates of corrosion in magnesium.

The discovery, reported in the journal Electrochemistry Communications, could have major implications for aerospace, automotive and electronics industries, making products lighter and more energy efficient.

The new alloy could be a real game changer according to Birbilis, who together with researchers at the CSIRO, the University of Wales and the Spainish Centro Nacional de Investigaciones Metalurgicas, has been working on the new formula for seven years.

"Magnesium has always been seen as a lightweight wonder metal with attempts to use it as a structural material for over a hundred years," says Birbilis.

"It's two-thirds [the weight of] aluminium, making it the lightest structural metal. But it's also the most prone to corrosion, limiting its use."

Green revolution

The growing worldwide search for strong lightweight structural materials, capable of reducing fuel consumption and carbon emissions, has seen renewed interest in magnesium.

Birbilis and colleagues tested more than 400 different alloy combinations to try and find ways of reducing magnesium's susceptibility to corrosion.

"The conventional stuff wasn't working, so we had to push the boundaries, looking for more obscure elements and more extreme options," says Birbilis.

When exposed to air, magnesium forms a thin oxide coating. But if it is placed in water, it corrodes quickly and releases hydrogen gas.

According to Birbilis, one set of experiments simply involved adding a variety of arsenic compounds to a beaker of water containing magnesium.

The initial experiments showed promise and were successfully repeated using solid magnesium alloys containing 0.37 per cent arsenic.

The researchers found that arsenic acts as a cathodic poison by restricting the ability of hydrogen atoms to form magnesium corroding molecules.

"This shows cathodic poisons are a real game changer," says Birbilis.

Magnesium cars

Birbilis sees non-corroding magnesium alloys being used as lightweight chassis for portable electronic devices, and replacing steel and aluminium in automotive engines, components and body panels.

"It's going to mean in ten years time we have it in our cars, and we have a slightly better quality of life with reduced emissions and lower petrol bills," says Birbilis.

"I see magnesium becoming a real threat to aluminium. Anywhere where aluminium is used now, you could potentially use magnesium instead."