Swansea University researchers have discovered a highly effective corrosion inhibitor for steel to replace the widely used hexavalent chromate, which will be banned across the European Union in 2019.

A team led by Professor Geraint Williams, of the university’s College of Engineering, discovered a material and manufacturing process for a smart-release coating that they say outperforms hexavalent chromate in laboratory tests. The new method involves a stored reservoir of corrosion inhibitor that operates by channeling aggressive electrolyte anions into the coating, triggering the release of the inhibitor on demand to prevent corrosion.

(Clockwise from left): Dr. Adrian Walters, Professor Geraint Williams and Patrick Dodds examine steel at the atomic level. Image credit: Swansea University. As part of their testing, the researchers used a scanning Kelvin probe, custom built by the team, that is capable of detecting the state of metal beneath a coating without touching it. This allowed them to judge the effectiveness of different coatings' ability to protect steel from salt spray—the standard test for corrosion—much more quickly, with each test taking around 24 hours, rather than 500 hours, as was previously the case.

“The system has been shown to prevent the onset of corrosion for over 24 hours, compared to less than 2 hours for the current market leader," says Patrick Dodds, of Tata Steel and a doctoral researcher at Swansea University. "We have also been able to demonstrate that the rate of corrosion can be slowed down significantly once it has started."

Corrosion inhibitors are commonly employed in a wide range of sectors, including coated steel products used to construct industrial, commercial and other buildings; aerospace and aircraft; and the automotive industry.