Corrosion - BMW i3

[TARDISi3]

I recently had off the rear right side tire and noticed a bolt 2 bolts holding something onto the body of the car that had rust on them.

When I open the front trunk area, I notice what looks to be the wiper motors in an aluminum housing, and I am seeing some aluminum oxidation.

There's also a black metal bar in the front trunk area that goes from one side of the car to the other that is displaying some surface rust at the ends.

Under the car, I notice some of the bolts that hold the battery to the car are also starting to rust.

I'm already adding lithium lubrication to the door locks because they falsely give a door open warning when the sensors get 'sticky'.

One of the reasons I bought the car is the fact that I should not expect any rusting plastic or carbon fiber parts, hahaha. What other areas of corrosion should I be aware of?

 

[spartacus68]

These cars are not immune from rust. Water, road salt, etc. Your suspension components will take a hammering, but its just one of these things. Brake discs and hubs too. Very much depends on your environment. In Europe you get a product like Lanogard which you can spray on sub frames and suspension components to keep rust at bay. Keep away from brakes for obvious reasons.

 

[GoldiE46]

"One of the reasons I bought the car is the fact that I should not expect any rusting plastic or carbon fiber parts, hahaha. What other areas of corrosion should I be aware of?"

your bolts, nuts, rotors, calipers, springs, and every metal piece will eventually rust out. As long as you don't see surface rust on your plastic, carbon fiber and glass components you shouldn't worry about the car. It's all normal.

 

[alohart]

your bolts, nuts, rotors, calipers, springs, and every metal piece will eventually rust out. As long as you don't see surface rust on your plastic, carbon fiber and glass components you shouldn't worry about the car. It's all normal.

Much of the metal that would be corrosion-prone steel in most cars is aluminum, CFRP, or thermoplastic in an i3. While it can corrode, the aluminum oxide corrosion forms a protective layer that inhibits further corrosion. I believe that the calipers are aluminum, but I can't recall for certain. Overall, there's much less to corrode destructively on an i3 which I appreciate in our humid, salty environment.

 

[eXodus]

Every Metal will rust. Many cars in the Rustbelt will not make for 10 years without holes in the bodywork.

Just would like to get some context here - in what kind of climate environments you guys are living?

But I'm wondering about rusting bolts here, since they are anodized these days and that holds up fairly well usually.
Maybe galvanic corrosion between the aluminum body and the metal bolts in the i3?

My old Volvo didn't get any rusty bolts on German salty roads. But it had rust on the bodywork.

 

[alohart]

Maybe galvanic corrosion between the aluminum body and the metal bolts in the i3?

The i3 doesn't have an aluminum body like our 2000 Honda Insight had. An i3's body is a CFRP passenger compartment with thermoplastic exterior panels, neither of which corrodes. Honda used specially coated single-use steel bolts to prevent galvanic corrosion of the aluminum body. The i3's frame and many of its suspension parts are aluminum, so BMW almost certainly has taken measures to prevent galvanic corrosion.

 

[eXodus]

Maybe galvanic corrosion between the aluminum body and the metal bolts in the i3?

The i3 doesn't have an aluminum body like our 2000 Honda Insight had. An i3's body is a CFRP passenger compartment with thermoplastic exterior panels, neither of which corrodes. Honda used specially coated single-use steel bolts to prevent galvanic corrosion of the aluminum body. The i3's frame and many of its suspension parts are aluminum, so BMW almost certainly has taken measures to prevent galvanic corrosion.

you are correct - the body of the i3 is CFRP

The drive module - where most of the bolts - is aluminum -

 

[TARDISi3]

Just would like to get some context here - in what kind of climate environments you guys are living?

I live about 200m from the ocean in a hot and humid climate. The strong breeze brings a steady spray of droplets that coats everything and gets everywhere. A piece of bare metal will start to rust in days if left outside, and some mornings when I come out to the car, I cannot see outside without first cleaning the windshield because there's so much salt accumulated on it overnight.

There is some rusting of some bolts, a pair on the right rear behind the back wheels. The aluminum wiper motors have a coating of corrosion, and aluminum under the car next to the electric motor also has surface corrosion. The ends of that black metal bar that go from one side to the other have some rust at the ends by the bolts. That's my experience so far.

 

[eXodus]

That Ocean spray salt probably explains the rusting.

"The ocean air also contains salt and minerals. In fact, the ocean contains over 70 mineral nutrients and trace elements (this is one reason why swimming in the ocean is considered therapeutic to the body – so many minerals)."

https://beachlifeexpert.com/tips/why-do-cars-rust-near-the-beach-sea/

If you are worried - I would coat the metal parts with a wax undercoating. I did this with my cars in heavy salted areas in the mountains.

Lanolin based, That stuff is a sacrificial layer. It's ugly to work with, but it helps.

 

[TARDISi3]

That Ocean spray salt probably explains the rusting.

"The ocean air also contains salt and minerals. In fact, the ocean contains over 70 mineral nutrients and trace elements (this is one reason why swimming in the ocean is considered therapeutic to the body – so many minerals)."

https://beachlifeexpert.com/tips/why-do-cars-rust-near-the-beach-sea/

If you are worried - I would coat the metal parts with a wax undercoating. I did this with my cars in heavy salted areas in the mountains.

Lanolin based, That stuff is a sacrificial layer. It's ugly to work with, but it helps.

Yessir! I have the fluid film ready for application!

 

[alohart]

I live about 200m from the ocean in a hot and humid climate. The strong breeze brings a steady spray of droplets that coats everything and gets everywhere.

Even though I live on the shore of a saltwater bay, there's no surf on this bay to create salt spray. I live on the leeward side of our island, so on most days, the trade winds blow across ~5 km of land and the salt water bay from a windward surf beach that generates salt spray. Our i3 spends almost all of its time parked in a parking garage with open sides that allow the wind to blow through. When departing after having been parked for a couple of days, I usually use the windshield washers to clear a thin salt film. The remaining windows become so fogged over after a couple of weeks that I need to wash them. In general, corrosion occurs more rapidly than in most climates.

The most visible corrosion occurs on our i3's brake rotors which shed rust dust that coats the inner surfaces of the wheels. When departing, I descend a parking garage ramp with a stop sign at the bottom that requires using the friction brakes. With walls on both sides of the ramp, the noise of the brake pads rubbing against the rusty surface of the rotors is very noticeable.

The good news is that with our i3 being in this environment over 6 years, corrosion in general hasn't been a problem. When I flushed the brake fluid recently, the brake fluid bleed valves weren't corroded at all and were easy to loosen. I removed each wheel and inspected the suspension and brake components. Other than the brake rotors and wheel hubs, I saw little corrosion. I'm happy with how our i3 is handling our salty, humid environment. Other cars don't fare as well.