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Raindrops Carry Electrical Charge, Study Finds

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In Short: Raindrops are not just water but tiny lightning bolts, according to a new study that could explain why they corrode cars.

Raindrops are not just water but tiny lightning bolts, according to a new study that could explain why they corrode cars. A team of researchers from the Max Planck Institute for Polymer Research in Mainz, Germany, has shown that water drops routinely arrive at a surface carrying an electrical charge large enough to punch through an insulating coating. The study, led by Zhongyuan Ni, Rüdiger Berger, and Hans-Jürgen Butt, was published in the journal PLoS ONE.

The standard explanation for why rain causes corrosion is that water carries dissolved salts and acids to a surface, constant drumming of raindrops abrades whatever protective coating is on it, and oxygen does the rest. However, the new study suggests that the electrical charge carried by raindrops plays a significant role in the corrosion process. When such charged droplets strike a coating, they discharge locally and can puncture the layer in specific spots like a small flash of lightning, with consequences for the coating's durability.

According to Dr. Rigosi and co-authors from Lund University and the University of Adelaide, the phenomenon of slide electrification, which has only been properly quantified in the past few years, is the starting point of the study. The researchers used a technique called intracellular recording to measure the electrical responses of individual photoreceptors in four bee species and both sexes of each, revealing the underlying mechanism of how energy-producing structures called mitochondria move through nerve cells.

The study's findings could have significant implications for industries that deal with corrosion, such as automotive and construction, as well as for the development of new protective coatings.

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