Water droplets may contribute to corrosion in a way scientists have largely overlooked. Researchers have found that water drops can acquire an electrical charge while sliding across surfaces and later transfer that charge to metals, triggering corrosion even when the metal has a protective coating, tells Science News.
Scientists already knew that water can become electrically charged as it moves across materials. The new research, published in Nature, connects this sliding electrification to corrosion. The effect could occur when water moves over leaves, windows, construction materials, and other surfaces. Droplets may also acquire charge in natural environments such as clouds, thunderstorms, and waterfalls.
To investigate, researchers led by Zhongyuan Ni of the Max Planck Institute for Polymer Research released water droplets onto Teflon-coated copper samples. Before striking the copper, the droplets slid across various common surfaces, which gave them an electrical charge. Early tests involving hundreds of droplets produced little visible damage. When the experiments continued for thousands of drops, however, corrosion became apparent.
Microscopic examination showed damage on samples exposed to sliding droplets. In contrast, samples receiving water drops that had not first slid across another surface showed no comparable deterioration. Further analysis revealed that the charged droplets penetrated the Teflon coating and corroded the underlying copper.
The researchers also observed deterioration in copper protected by polystyrene glass and in gold samples, suggesting that the phenomenon extends beyond a single metal or protective material.
Individual charged droplets cause only tiny effects, but repeated exposure could become significant over years. That makes the findings relevant to bridges, ships, cars, monuments, machinery, and other structures exposed to rain and moisture.
The research adds electrical charge to known corrosion mechanisms such as droplet impact and chemical contaminants. Understanding this process could also help engineers develop anticorrosion coatings that better protect infrastructure against long-term environmental exposure.
