Water droplets sliding across surfaces can become electrically charged and accelerate corrosion, even on protected materials, according to research led by Zhongyuan Ni. The effect, observed on Teflon-coated copper, could have significant economic implications.
Researchers at the Max Planck Institute for Polymer Research in Mainz, Germany, discovered that water drops gain an electrical charge as they slide down surfaces like leaves and polystyrene glass. When these charged drops land on metals, they can penetrate protective coatings and cause corrosion. Initial experiments showed no damage after a few hundred drops, but extended testing revealed damage after thousands of drops impacted Teflon-coated copper. The team found that samples hit with sliding drops showed damage under a microscope, while those hit with direct drops did not.
Zhongyuan Ni, a physicist at the Max Planck Institute for Polymer Research, explained the accidental discovery: “One day, I just let the experiment [keep] running. I forget; I [went] to drink coffee or something.” Upon returning, he observed signs of damage, prompting further investigation.
The study, published August 26 in *Nature*, suggests that this phenomenon may be widespread, as water can also become charged in clouds, thunderstorms, and waterfalls. Corrosion currently costs the U.S. automotive industry over $30 billion annually (as of 1999) and has a global economic impact in the trillions. Stefan Weber, a physicist at the University of Stuttgart in Germany who was not involved in the study, believes this work could lead to the development of improved anticorrosion coatings. He noted that earlier research had already shown water drops become charged through sliding, but identifying this as a source of corrosion is a significant advancement.
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