Electrically charged raindrops could be corroding metal with protective coatings

Electrically charged raindrops can corrode metal surfaces treated with protective coatings, according to new research in Nature. This previously unconsidered corrosion mechanism highlights the necessity for new methods to safeguard metal objects like cars, ships, buildings, and cultural heritage sites. Traditionally, corrosion from rain was attributed to physical abrasion or acidic pollutants, but recent studies have shown that water drops can become electrically charged after sliding over surfaces like plant leaves and window glass.

The charge itself may contribute to corroding metal surfaces. Researchers analyzed how neutral water drops become charged and corrode different materials, dropping water onto common surfaces and observing the resulting electrical charge. When these charged drops fell onto Teflon-coated copper after 3,000 impacts, the protective coating degraded and the underlying metal corroded; drops with no charge caused no detectable damage.

Further research is required to explore ways to prevent corrosion under these conditions and enhance materials designed to protect outdoor metal structures.