Graphene has been touted as a miracle material in electronics; now it can stop rust.
Keeping rust off steel — especially on a car — is often a losing battle. The body is protected by the paint, but that can scratch. Bumpers are coated in chrome, but the process involves toxic chemicals.
To get around that, SUNY Buffalo chemistry professor Sarbajit Banerjee and Robert Dennis, a PhD student, experimented with a polymer composite that contains graphene. Graphene is a single layer of carbon atoms and it repels water. It's also highly conductive. That combination keeps steel from coming in contact with water and also slows down the electrochemical reactions that oxidize iron to make rust.
The two researchers made the coating into a varnish, painted some steel with it and dipped it in brine. Brine is not unlike the mix of salt and slush a car in a typical winter climate will encounter, so as a stand-in for a very harsh environment, it works well.
At first, pieces of steel coated with the varnish lasted only a few days when immersed continuously in the salt water. But by adjusting the concentration and dispersion of graphene within the composite, Banerjee and Dennis were able to get the varnish to hold up for a month.
Banerjee told Discovery News that he wants to include something in the coating that will detect a change in the pH level of water near where a scratch occurs, and react with the water in a way that would seal the crack.
While this technique is a long way from being commercialized, there's interest from some big players in the steel industry, notably Tata Steel, which has provided funding for Banerjee's experiments before. The two scientists also got a $50,000 grant from the New York State Pollution Prevention Institute. Banerjee said in a press release that the coating can be made with existing equipment at local steel plants.
Unlike hexavalent chromium, which is used to coat bumpers and some engines, graphene isn't toxic, as it is just carbon. It also doesn't require strong acids to be applied. That's one reason the Pullution Prevention Institute is interested.
Credit: SUNY Buffalo