Some EVs Are Developing Serious Rust Problems — and the Location Makes It a Safety Issue

Rust is supposed to be a solved problem in modern cars. Decades of galvanizing technology, improved coatings, and better steel have largely eliminated the floor pan and body panel corrosion that plagued vehicles from the 1970s and 1980s. But a growing number of EV owners are discovering that their vehicles have a corrosion problem in an unexpected place: underneath the vehicle, on components that weren’t anticipated to be an issue.

The specific concern is with the underbody battery trays, mounting structures, and associated hardware on several EV models. Because battery packs sit low in the vehicle — typically mounted along the floor — the components that support and protect them are constantly exposed to road spray, salt, water, and debris. Early generation EVs didn’t have decades of real-world corrosion data to draw on, and some manufacturers apparently didn’t fully anticipate the rate at which certain materials and coatings would degrade under those conditions.

Owner forums for several EV brands have threads documenting significant corrosion on vehicles only a few years old — in some cases impacting the structural integrity of battery enclosures. The implications aren’t just cosmetic. A compromised battery enclosure can affect the seal that protects the battery from water intrusion, which is directly relevant to the fire risk we’ve discussed elsewhere. It can also affect how the vehicle behaves in a crash if the structural elements are weakened.

This is a quality and durability story that will take years to fully understand. EVs are still a relatively young technology in mass market terms, and the long-term reliability data that exists for combustion vehicles — which have been refined over more than a century — simply doesn’t exist for EVs yet. Corrosion is one area where real-world experience is revealing design and materials choices that will need to be addressed in subsequent model generations. It’s a useful reminder that ‘new technology’ doesn’t automatically mean ‘better in all dimensions.’