Are you sure it's coming from the Alubottle ?
Is your Alubottle or balls black ? If neither of them are black, it may not be the cause.
The only other source of black color besides the bottle or balls itself, would be the "print", but that's only on the outside of the container.
If it's coming from the bottle or balls, I would think you'd be able to find the source of where the plastic chipped off, by finding the areas that's missing the black plastic. If you can't find such "missing areas" then maybe it's from another cause, like the kava itself ?
I've always used the original Aluball maker, not the newer Alubottle, and have never ever had that problem.
First I'd contact Kavafied and see how they can help