After an accidental discovery, researchers at ETH Zurich have developed an extraordinary protection against corrosion. It glows where it is not damaged, is naturally repaired, and can be reused many times.
Skyscrapers, bridges, ships, planes, cars – everything man made or made will collapse sooner or later. Damage over time is known as corrosion. Nothing is safe from it.
This makes fighting corrosion costly. All countries together invest about 3.5% of the world’s total gross domestic product annually in corrosion protection, which amounts to about $4 trillion. This is a huge market and a huge problem.
Researchers at ETH Zurich, led by Markus Niederberger and Walter Caseri of the Institute for Multifunctional Materials, have presented a new solution. Over the past few years, they have developed plastics that can greatly improve and simplify corrosion protection. Poly(phenylene methylene) is the name of the miracle material, PPM for short.
This new anti-corrosion material kills two birds with one stone. When mixed as a paint and heated, PPM can be sprayed onto surfaces and becomes a solid. The polymer indicates holes or cracks in the protective layer by not fluorescing.
Moreover, it repairs the damage itself without further external intervention. And at the end of the product’s life, the polymer can be completely removed and recycled with minimal material loss. Recycled polymers can be applied to different surfaces without losing their special properties and functions.
Chance reached out a helping hand
The impetus for this development was purely accidental. About ten years ago, researchers in Niederberger’s lab were working on the production of nanoparticles in special organic solvents. Under certain conditions the solvent became solid and polymerized. “It was unintentional and undesirable,” recalls Niederberger. “We didn’t know what to do at first either.”
But then they discovered that the polymer they accidentally made (known as PPM) had other interesting properties in addition to its high thermal stability. It did fluoresce, even though conventional wisdom suggested it shouldn’t fluoresce at all. Therefore, researchers specially modified the material. First, a PhD student improved the synthesis of the polymer. His successor, PhD student Marco Delia, was then tasked with finding useful applications for PPM.
“And he’s done it brilliantly,” says Walter Caseri, who directed D’Elia. Contact with corrosion specialists at the Università degli Studi di Milano has also been fruitful, says Caseri.
Easy to use and versatile
Laboratory tests have revealed that PPM-based coatings protect metals, especially aluminum, from corrosion. This protective coating can be applied up to 10 times thinner than traditional protectants (such as those based on epoxy resin) yet is durable.
Last but not least, the polymer itself will seal damage to the coating. “Self-healing mechanisms are in great demand, but are very difficult to achieve and good solutions are still rare,” he says Caseri. A chemical additive is usually required to achieve self-healing. Chemical additives migrate into the polymer over time and are released into the environment. Not so with PPM.
PPM is also more sustainable than previous anti-corrosion materials as it can be completely removed and recycled at the end of its life. Some polymer material is lost in the process, but the recycling rate is very high at 95%. In tests, the researcher was able to reuse the material five times.
Studies on the sustainability of PPM-based corrosion protection have also shown that polymers outperform epoxy-based corrosion protection materials in terms of both environmental impact and human health. “He has only two options for disposing of epoxy resin: incineration or landfill,” D’Elia says. “Our products enable a third solution: recycling.”
“The project shows the diversity of materials science”
Nevertheless, PPM corrosion protection is not completely harmless to the environment. “Synthetic products always have an impact,” says D’Elia. “But if you choose the right approach, you can greatly reduce that impact.” A former PhD student wants to commercialize PPM corrosion protection.
The researchers have applied for a patent for their invention. it is still pending. We are also currently looking for industry partners to further develop, manufacture and distribute our products on a large scale. Given the size of the global market, D’Elia believes he sees great potential in PPM. “Our technology is pretty advanced, but there are still some things we need to improve before we can sell it as a product,” he says.
Caseri, on the other hand, is proud of her accomplishments. The chemical synthesis, the characterization of the molecular structure of PPMs, and the study of material properties such as fluorescence, which were not expected for this type of polymer, demonstrate the ‘all diversity of materials science’.
In addition, manufacturing, another of his division’s mainstays, also saw a bright spot, he said. “And now we have a great application. In this project, we covered all these basic elements of materials science.”
It also shows how important international cooperation is. For this project, ETH researchers collaborated with partner universities in Spain, Austria, Italy, and the UK.
Original: A new self-repairing anticorrosive
Than: ETH Zurich | Milan University of Bicocca
