Whether on a car, a garden fence, or a ship: a coat of paint protects against rust.
Whether on a car, a garden fence, or a ship: a coat of paint protects against rust. But water takes its toll on any coating—from a rain shower to ocean waves. Until now, the damage was primarily attributed to mechanical wear on the surface or to interactions with acidic components in the droplets. Researchers at the Max Planck Institute for Polymer Research, led by Director Hans-Jürgen Butt, have now identified a previously unknown factor in collaboration with the Universities of Darmstadt and Bonn: the electrical charge of water droplets. They show that this charge damages surfaces over time—an effect that could open up new approaches for more durable coatings.
Many people are familiar with this from everyday life: the paint on a garden fence needs to be repainted after a few years—“the weather has taken its toll.” But even larger structures, from the Eiffel Tower to the Golden Gate Bridge, must be time-consuming repainted to maintain them. Until now, two main causes were considered the driving forces behind such damage to coatings: first, mechanical stress—that is, a kind of friction between droplets and the surface that gradually wears down the coating or causes it to flake off; and second, chemical factors, particularly when droplets contain acids or salts.
Read More: Max Planck Institute for Polymer Research
Image: Drops can become electrically charged as they slide across surfaces. If they then fall onto a coating—such as on a car—the coating can be corroded by the drop’s electrical discharge and permanently damaged. (Credit: (c) Katharina Maisenbacher / MPI-P)
