Hello all. I was out looking at my bike the other day and noticed this:



It sure looks like rust to me and I was wondering if I need to replace the rotor, gently sand it off, or ???

The bike lives under an EZ-up year round in Portland, OR, so it doesn't get the garage-treatment it deserves. I am looking at the possibility of buying a carport instead to get that extra coverage. It's been under an EZ-up for it's entire life (bought new in 2009 - pre firesale) and this is the first I've seen of it, although it gets ridden less these days than it did initially.

Thanks in advance for your input!

Here are a few more pics if needed: