Threat from above Water droplets can become electrically charged as they slide across surfaces. If they then fall onto coated metal – such as a car body – the coating can be corroded by the droplet’s electrical discharge and permanently damaged. (Courtesy: Katharina Maisenbacher/MPI-P)"> Threat from above Water droplets can become electrically charged as they slide across surfaces. If they then fall onto coated metal – such as a car body – the coating can be corroded by the droplet’s electrical discharge and permanently damaged. (Courtesy: Katharina Maisenbacher/MPI-P)

Water droplets sliding across solid surfaces can acquire electric potentials of thousands of volts and thereby corrode non-conductive surfaces on metals when they discharge.…