Electrically Charged Water May Trigger a Hidden Form of Metal Corrosion

Metals used in everything from cherished cars to landmark buildings, sculptures and ships require protection against corrosion.

New research, however, points to an unrecognised source of corrosion that has not previously been taken into account: electrically charged water.

Electrically charged water and corrosion

Water can acquire an electrical charge in numerous ways, including by travelling through a thundercloud or sliding over various surfaces.

Since water can become charged as well as corrode metal, researchers at Germany's Max Planck Institute for Polymer Research investigated whether these two effects could be linked.

Their tests found that electrically charged water can puncture a standard protective coating on copper through the powerful electrical mechanism called dielectric breakdown.

"We demonstrated that these charged drops can cause the coating to break down electrically and lead to corrosion of the metal," write the researchers in their published paper.

"As spontaneously charged water drops form naturally, this previously overlooked corrosion mechanism may contribute to the degradation of cultural heritage sites, buildings, ships, cars and other metal components."

How the experiments tested protective coatings

The team performed a sequence of experiments involving varied materials and arrangements.

The team found that electrical charge accumulated while water droplets travelled across surfaces, harming different materials to different extents. (Ni et al., Nature, 2026)

For the first experiment, droplets of water rolled over four widely used surfaces - a plant leaf, a thin PVC foam board, polystyrene, and water-repellent-coated quartz - before dropping onto copper samples protected with either Teflon or polystyrene.

In a separate set-up, droplets slid along an unbroken Teflon layer that covered two neighbouring materials.

The researchers recorded the droplets' charge as they moved, then examined corrosion patterns after many thousands of droplets had either struck or travelled over the coated metal surfaces.

Taken together, the tests revealed that droplets could damage coated metals such as copper and gold not merely when they hit the surfaces, but simply while moving across them.

With a high-powered microscopy method, the team was able to observe the damage and identify the products generated by the corrosive reactions.

No damage was seen when electrically neutral water droplets were applied to the protected copper.

Magnified views of some damage seen in metal coatings after 3,000 charged droplets. (Ni et al., Nature, 2026)

Scientists only recently established that water droplets in motion can gain charge by exchanging charges with a surface, much like static electricity does.

This latest research advances understanding of the effects these charged droplets can have on commonplace materials.

Implications for corrosion protection

After a metal surface has been exposed, corrosion can take hold. Scientists have long known that rain and water degrade metals; what may need revising is how this damage is assigned to particular causes and how it is prevented.

"Conventional understanding attributes the coating failure induced by water drops mainly to two mechanisms: physical abrasion caused by moving drops, and chemical degradation from acidic substances and pollutants in the drop," write the researchers.

The findings are revealing, though the work was confined to laboratory experiments. It remains uncertain, for instance, how much rainwater may carry an electrical charge large enough to harm metal.

Even so, it is a genuine possibility. Further research should clarify how much material deterioration can be attributed to electrically charged water droplets.

"Charged drops can be generated naturally in clouds, thunderstorms, ocean waves, fountains, and waterfalls, or when sliding over hydrophobic materials before hitting the coated metal," write the researchers.

"They also occur in industrial processes such as electrostatic spraying, inkjet printing and reactions in chemical and pharmaceutical production. Consequently, this cause of corrosion may be relevant in many everyday or industrial processes."

If scientists can more accurately measure the risk that electrically charged water poses to protected metals, they may be able to create better coatings that resist the dielectric breakdown documented in this work.

Now that the researchers know what signs to seek, they consider it likely that comparable corrosion is occurring in materials beyond those included in their experiments.

Related: Most Materials Seem to Obey a 'Rule of Four' And Scientists Are Utterly Stumped

"Naturally charged drops can cause a coating to break down electrically, thereby initiating or exacerbating corrosion of the coated metals," write the researchers.

"Our findings can improve anti-corrosion strategies and emphasize the need for protective materials capable of resisting charge-induced damage from water drops."

The research was published in Nature.

This article was fact-checked and edited by Clare Watson. Although we take pride in our process, we are only human. If you notice an error, please let us know.