Graphene, the highly useful material consisting of a one-atom-thick sheet of linked carbon atoms, has already been shown to keep steel from rusting. Soon, though, it could also be used to stop bacteria from corroding metal pipes.
In wastewater-handling facilities such as sewage treatment plants, microbes known as sulfate-reducing bacteria frequently colonize the inside surfaces of pipes and other equipment. Taking the form of what are known as "biofilms," the resulting bacterial colonies can develop in as little as 10 days after the pipes have been cleaned, and they proceed to degrade those pipes in two main ways.
First, the microbes extract electrons from the surface of the metal as they respire. Second, as the bacteria consume organic matter in the water, they produce corrosive hydrogen sulfide.
And while protective polymer coatings can be applied to the inside of pipes, these may themselves be degraded as the bacteria consume the plasticizers within them. Additionally, such coatings can become brittle over time, subsequently cracking, flaking off, and entering the water stream.
With these limitations in mind, South Dakota School of Mines & Technology research scientist Govind Chilkoor looked instead to the use of graphene as a coating. In lab tests, he found that even a single layer of graphene – measuring less than 1 nanometer thick – was highly effective at keeping sulfate-reducing bacteria from latching onto the inside surface of metal pipes.
"Graphene can be very antimicrobial," he explains. "It can induce oxidative stress and the bacteria will die."
Additionally, given that graphene is one of the strongest manmade materials, it ought to be much more durable than the polymers currently used in protective coatings. And as an added bonus, because graphene is very thermally-conductive, it should perform better than polymers when utilized in heat-exchanging pipes.