Raindrops can cause car corrosion via electrical charge, study finds

A new study from Germany's Max Planck Institute for Polymer Research suggests that raindrops can carry significant electrical charges, capable of damaging protective coatings on surfaces. This finding challenges the conventional understanding of how rain leads to corrosion.

The research indicates that water droplets can become electrically charged when sliding across insulating materials like car paint or plastic panels. This phenomenon, known as "slide electrification," has been measured to produce voltages of up to 9,000 volts in the droplets.

When a charged raindrop impacts a surface, its electrical discharge can create a small hole in the protective layer, rather than merely abrading or dissolving it over time. This direct damage then exposes the underlying material to accelerated corrosion.

Previously, corrosion from rain was primarily attributed to dissolved salts and acids, mechanical abrasion from the impact, and exposure to oxygen. The study introduces the electrical discharge mechanism as a previously underestimated factor.

Led by Zhongyuan Ni, Rüdiger Berger, and Hans-Jürgen Butt, the research highlights the significant role of electrical effects in the degradation of protected surfaces.