Study Reveals Electrical Charge in Raindrops Contributes to Car Corrosion

<p>A study conducted by Zhongyuan Ni, Rüdiger Berger, and Hans-Jürgen Butt at the Max Planck Institute for Polymer Research in Mainz, Germany, has found that raindrops can carry an electrical charge that contributes to corrosion on surfaces, including cars. The traditional understanding of rain-induced corrosion involves water carrying dissolved salts and acids, which abrade protective coatings and allow oxygen to cause further damage.</p><p>The researchers discovered that water drops can arrive at surfaces with a significant electrical charge, which can penetrate insulating coatings. This process is not merely a result of scratching or dissolving the coating but can create holes in it, similar to how a spark jumps a gap.</p><h2>Charged Rain</h2><p>The study focuses on a phenomenon known as "slide electrification," which has been quantified more accurately in recent years. When a water drop slides across an insulating surface—such as a leaf, painted wall, windowpane, or plastic panel—it strips charge from that surface, leaving an opposing charge behind. The voltages generated by this process can be substantial, with drops measured at up to 9,000 volts.</p>