CLR usually works quite well for stuff like this. It's a spray cleaner. I think it stands for Calcium, Lime, Rust remover.

Yes, and I think, potentially, that it could be so advanced that we don't have the ability to recognize some or all of them.

Yeah, thank's lol

I would replace it with something that doesn't rot, like Hardie Sierra 8. It's expensive, but if installed correctly it'll last forever.

Reminds me of the trace buster buster buster