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I have a 1976 C3, I'm replacing the battery and the compartment can use a good detailing. I had originally thought the compartment was made of metal as there is a "rusty" residue all over it that I was going to start sanding off. But I found on this forum the box is made of fiberglass? it looks plastic to me now. How did this rusty coating happen on fiberglass/plastic? I read something about "vents"? There is a hole in the bottom of the compartment. Would a new sealed maintenance free battery cause the same issue? What's the recommended way to clean-up and restore the box? sandpaper and black spray paint? I have some POR-15 I was going to use on the undercarriage, how about that?
If you Google C3 battery box image you will see none of them have that coating, they are all black.
Older C3's used special battery caps that had a vent hose attached running out the bottom of the box.
Later C3' with sealed batteries or aftermarket sealed batteries do not need the special caps.
The coating was not put on by anyone, it seems to be some chemical reaction of residue, like rust, but maybe acid? It's not 100% covered as you can see.
If the battery used was non-sealed (non-maintenance free) in the newer C3 (without vents), could this residue be produced by the battery gasses?
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2022 C3 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
I bought my '76 new & I have that same overspray coating on the right side of the box.
It also has some at the rear & on the bottom. The front is clean glass.
I also noticed some bright blue metallic mixed in with the black....it's all stock.
Is your '76 red?
The coating was not put on by anyone, it seems to be some chemical reaction of residue, like rust, but maybe acid? It's not 100% covered as you can see.
If the battery used was non-sealed (non-maintenance free) in the newer C3 (without vents), could this residue be produced by the battery gasses?
I haven't seen a battery that needs maintenance in decades.
Take a small amount of water and a small amount of baking soda and mix.
Take a small paint brush or some sort of applicator and apply it to the discolored area in a small spot to see if there is a reaction to determine if you have any acidic substance present,
Detailing battery compartment
