Abstract:
Research by German scientists shows that as a naturally occurring phenomenon, charged raindrops can break down surfaces treated with protective coatings. This previously overlooked corrosion mechanism could help find new ways to protect metal objects such as cars, ships, buildings and cultural sites. Relevant research was recently published in Nature.
Corrosion is an economic and safety issue for outdoor metal products and structures. It was previously thought that corrosion caused by rainwater was mainly due to the physical corrosive nature of raindrops or the acidity from pollutants. While previous research has shown that water droplets become charged as they slide across common surfaces, such as plant leaves and window panes, the corrosive effect of this charge on metal surfaces has been overlooked.
Rudiger Berger, Hans-Jurgen Butt and colleagues from the Max Planck Institute for Polymer Research analyzed how electrically neutral water droplets become charged and corrode different materials. They dripped water onto four common surfaces - plant leaves, PVC (polyvinyl chloride) foam board, polystyrene glass, and the commonly used hydrophobic coating PFOTS (perfluorooctyltriethoxysilane). These water droplets then slide onto the Teflon-coated copper. The researchers found that the water droplets carried a very weak charge (0.2-2 nanocoulombs). After 3,000 water droplets were dropped from these surfaces onto Teflon-coated copper, the coating was observed to break down, causing the underlying metal to corrode. If the water droplets were uncharged, no surface damage would be observed.
Further research is needed to analyze how to reduce corrosion in these situations and to improve the materials used to protect ships, cars and buildings.
Related paper information:
https://doi.org/10.1038/s41586-026-10941-6
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