Science News · Wetenschap

Charged water droplets may cause corrosion

Researchers have discovered that water droplets, after sliding along surfaces and accumulating an electrical charge, can transfer this charge upon impact, leading to material corrosion. This phenomenon can occur even when materials are protected by coatings and may be widespread, potentially affecting cars, infrastructure, and heritage sites.

Water drops can become electrically charged by sliding along surfaces. When these charged drops land on materials with suitable electrical properties, such as metals, they can initiate corrosion. This process can occur even through protective coatings. The researchers reported their findings on August 26 in Nature. The charging of water in environments like clouds, thunderstorms, and waterfalls suggests this effect could be common.

The corrosion caused by these charged droplets could lead to the development of improved anticorrosion coatings. Previous research had established that sliding water drops could acquire a charge, but identifying this as a cause of corrosion is a significant advancement. The economic impact of corrosion is substantial, with the U.S. automotive industry alone losing over $30 billion in 1999, and global costs estimated in the trillions.

While physical impact and corrosive compounds in water were previously considered primary causes of damage, the role of electrified drops was initially unclear. Experiments showed that thousands of charged drops, created by sliding them along surfaces like leaves and polystyrene glass, were needed to cause observable damage to Teflon-coated copper. Drops without prior sliding did not cause similar damage. Microscopic examination revealed that the charged drops penetrated the Teflon coating and corroded the underlying copper. Similar corrosion was observed on polystyrene glass-coated copper and gold, indicating the phenomenon is not limited to Teflon.

Although the effects of these charged drops are small individually, they can accumulate over time and contribute to the deterioration of exposed materials like monuments, machinery, and infrastructure. Researchers emphasize that even small charges should not be overlooked due to their potential long-term significance.

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