Corrosion resistance

Scientists at the US Department of Energy’s Brookhaven National Laboratory have patented an ultrathin film that, when used to coat metal surfaces, makes them resistant to corrosion and eliminates the need for hexavalent chromium.

The Engineer Online has discovered that the corrosion-resistant coating is derived from a partially cross-linked amido-functionalised silanol component in combination with rare-earth metal oxide nanoparticles, particularly cerium acetate. 

According to chemist Toshifumi Sugama, a researcher at Brookhaven and the inventor of the coating, it can be produced on a metal using a simple two- or three-step process.

Corrosion resistance is essential for metals used in a range of applications, including electronics, aviation and power plants.

Hexavalent chromium has traditionally provided the best corrosion resistance but it is toxic to humans and can pollute the environment.

Sugama’s new coating achieves several goals - low toxicity and excellent corrosion resistance in a film measuring less than 10 nanometres.

It can be applied to an array of metals, including aluminium, steel, nickel, zinc, copper, bronze and brass.

According to Sugama, the coating is suitable for industries that produce coated valves, pumps and other components, as well as the manufacturers of aluminium fins used in air-cooled condensers at geothermal power plants, where preventing brine-induced corrosion is a high priority.

The coating can be made in a variety of ways.

In one embodiment, it starts as a liquid solution that can be sprayed onto the metal, or the metal can be dipped into it.

The metal is then subjected to one or more treatment steps, sometimes including heating for a period of time, to trigger cross-linking reactions between the compounds and to simultaneously form corrosion-inhibiting metal-oxide nanoparticles, such as environmentally benign cerium-based oxides.

The corrosion resistance of the coating can be comparable and even superior to chromium-based coatings and provides even better coverage of metal surfaces than chromium coatings, according to the researcher.

In an exclusive interview with The Engineer Online, Dr Poornima Upadhya, a licensing associate at Brookhaven’s Office of Intellectual Property and sponsored research in New York, said a number of manufacturers have expressed interest in licensing the technology, although no licensees have been signed as yet.

Upadhya was unable to divulge any names, as that information still remains confidential.

The terms of any licence will be negotiated with any potential licensee, and the terms would depend on how the coating technology would be used.

At present, the process has only been established at a bench-scale and further development is needed to take it up to a full-scale process and to optimise it for specific metal components.

For information about licensing the technology, Poornima Upadhya can be contacted by telephone on 631-344-4711 or through email at pupadhya@bnl.gov