New corrosion protection that repairs itself

ETH Zurich (ETHZ) researchers have developed an extraordinary protection against corrosion after a chance discovery. It glows in places where it is not damaged, repairs itself - and can be reused multiple times.

Worldwide, all countries together spend about 3.5 percent of their gross domestic product annually on corrosion protection, which amounts to about $ 4,000 billion: a huge problem.

Researchers at ETH Zurich's Laboratory of Multifunctional Materials have now come up with a new solution. In recent years they have developed a plastic that can greatly improve and simplify corrosion protection. The trick: polyphenylene methylene, PPM.

When mixed as paint and heated, PPM can be sprayed onto a surface and becomes solid. The polymer indicates holes and cracks in the protective layer by failing to fluoresce. What’s more, it repairs any damage itself without further external intervention. And at the end of a product’s life, the polymer can be completely removed and recycled with only minimal material loss. The recycled polymer can then be applied to another surface with no loss in its special properties and functions.

The discovery was purely accidental. About ten years ago, researchers at ETHZ were working on the production of nanoparticles in a special organic solvent. Under certain conditions, the solvent became solid: it surprisingly polymerised. They discovered that the polymer - known as PPM - had another interesting property in addition to its high thermal stability: it fluoresced even though conventional knowledge suggested it should not be fluorescent at all. They started to refine the material and improved the polymer’s synthesis. After that, doctoral student Marco D’Elia, was given the task of finding a useful application for PPM. And that’s what happened.

Laboratory tests revealed that a PPMbased coating protects metals, especially aluminium, well against corrosion The coating can be applied in layers that are up to ten times thinner than conventional protective equipment. Moreover, the polymer seals any damage to the coating by itself.

According to ETHZ, PPM is also more sustainable than previous corrosion protection materials because it can be completely removed and recycled at the end of the product’s life. While some polymer material is lost in the process, the recycling rate is very high at 95 percent. In their tests, the researchers were able to reuse the material five times.

Studies on the sustainability of PPMbased corrosion protection also show that the polymer performs better than epoxy-based corrosion protection materials when it comes to both environmental impact and human health.

The article ‘Smart Anticorrosion Coatings Based on Poly(phenylene methylene): An Assessment of the Intrinsic Self-Healing Behavior of the Copolymer’ was published las February in Polymers. It is online>

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