Plastic Polymer to Replace Barrier Method?

A plastic coating that virtually eliminates rust and corrosion — an innovation which could help metals last up to 10 times longer — has been described at the 220th national meeting of the American Chemical Society.

The coating, polyaniline, can be applied to nearly any metal, said Professor Bernhard Wessling, president and managing partner of German firm, Ormecon Chemie GmbH & Co.

Rusting and corrosion can be delayed by painting a metal or plating it with zinc or another, more reactive metal.

Zinc leaves the metal underneath unaffected, but there is a limit to the usefulness of paint and zinc coatings. Polyaniline, a catalyst that mediates the reaction that leads to rust, creates a physical barrier. The polymer accepts electrons from the metal and, in turn, donates them to oxygen. This two-step reaction forms a layer of pure iron oxide that halts corrosion.

Tests showed that polyaniline prevented rust 10,000 times more effectively than zinc, reported Wessling. In field tests, it proved three to 10 times more effective and this, according to Wessling, is enough to outlast the usefulness of most metal products.

The polymer coating compares favourably to zinc in that it is not a heavy metal and will have no potential impact on the food chain. Production of the polymer may, according to Wessling, prove economical as it is cheaper than zinc.

On the web: www.zipperling.de