Chrome replacement

For many years, chrome has been used to add a protective coating and shiny lustre to a wide range of metal products, from bathroom fixtures to car bumpers.

Chrome adds beauty and durability, but those features come at a heavy cost.

Although it is inexpensive to produce, the industrial process to create it is dangerous for workers and pollutes the environment.

'People have been trying to replace it for a very long time,' said Christopher Schuh, Massachusetts Institute of Technology (MIT) associate professor of materials science and engineering.

'The problem is that it's the only plated metal coating that has all of these properties - hardness, long-lasting shine and corrosion protection,' he added.

Until now, that is.

Schuh and his collaborators have developed a new nickel-tungsten alloy that, they claim, is not only safer than chrome but also more durable.

The new coating, which is now being tested on the bumpers of a truck fleet, could also replace chrome in engine parts, among other applications.

Chrome's hardness comes from its nanocrystalline structure.

So Schuh and his group set out to duplicate that structure with a material that could be easily and safely electroplated.

Using computer models developed to predict material properties, Schuh settled on a nickel-tungsten alloy that is environmentally friendly and proved to be even more durable than chrome.

Schuh's team showed that the nickel-tungsten alloy remains stable indefinitely at room temperature and is highly resistant to decomposition when heated. 

It can also be made harder and longer-lasting than chrome.

In addition, the electroplating process used to coat products with the alloy is more efficient than the one used for chrome, because multiple layers can be applied in one step, which could save money for manufacturers.

The technology could be used to coat other products, including shock absorbers and print rolls.

Recent tests showed that print rolls coated with the new alloy lasted 10 times longer than their chrome-plated counterparts.

Another field of potential applications is electronics, particularly connectors for portable electronics.

Those connectors are now coated with a layer of gold, which must be thick to help prevent the corrosion of an inner layer of brass.

Layering the nickel-tungsten alloy between the gold and brass layers could reduce corrosion and offer significant savings for electronics manufacturers by allowing them to use thinner layers of gold.