The rust on the bolts of a battery pack from a Model S was concerning.

Could a car with an aluminium body ever have rust problems? The video above, from Gruber Motor Company, shows it can. Not on the body itself, obviously, but rather on its battery pack. Almost all bolts on the battery pack cover of this Tesla have rusted so badly over almost nine years that Pete Gruber said his team had a hard time removing them.

The 2012 Model S came from San Diego, and it had a range of 17 miles when the company got it. Originally, the car would offer around 200 miles, according to the video description. When they took out the battery pack in search of the issue, they discovered how badly rusted the cover bolts were.

Tesla Vehicles Should Beware Of Coastal Cities, Says Gruber Motors

The surprising bit is that these bolts were under an intumescent fire suppression blanket. This device aimed to reduce any fire risk with the battery pack: when it is exposed to flames or high temperatures, it expands. In this Model S, it should also provide another barrier against rust by protecting the bolts from salt air. In this case, it didn’t.

That inspired Pete Gruber to not only talk about the repair in this car but also to warn about the dangers these Tesla battery packs may face if used in coastal cities. Ironically, Tesla was founded in Palo Alto, and its main factory is in Fremont, both of which are in the San Francisco Bay area – or else, by the sea.

Gruber mentioned that salt air consists of chloride ion migration, which is the cause of rust in iron components. He also discovered that half of the world’s population would live in coastal areas, which shows how important it would be for Tesla to have used stainless steel bolts in the battery pack.

More than that, Gruber’s concern is with other Tesla vehicles in coastal cities. He believes they may not have these steel components properly protected against salt air, as was the case for this 2012 Model S.

When it comes to the battery pack issue, it was apparently caused by another parasitic cell such as the one Gruber Motor Company fixed back in December. The company snipped it out of the circuit. In the previous repair, that cost $5,000 (£3,700). Pete Gruber did not mention the price in this case.