deskthority

Will my PCB still function properly ?
Thanks.

I think it's cupric oxide. It won't eat all the way through the copper traces, it's not the same as iron rust. In fact, a black oxide layer is sometimes used to protect the underlying metallic copper. It looks ugly, but it shouldn't affect the performance of the PCB, I reckon.

That's comforting to know, thank you so much for taking the time to answer.
There's also some corrosion on the pads, what should I do about them?

It's hopeless. Just send that beam spring board to me for proper disposal.

Really though, just spray the pads with some contact cleaner (e.g. DeoxIT D5), then insert/remove the connector a few times.

You could tin the pads and then wick it off , that would protect them. In fact i would recommend it !

That crap under the solder mask should be ok.