Surface rust on bottom side of fender

I took my front fender off of my kz650 today and notice that there was some surface rust on the bottom side of the fender and it got me a little worried. This is a nice fender and I don't want to have to worry about rust.

What can I do to prevent rust from coming back? I was wondering about straying on some of the spray-on bed liner stuff.

What have you guys done to protect yourselves?

If it's just surface rust (not pitted), just use some steel wool to knock it off. If it's pitted, then steel wool it, then treat it with phosphoric acid, available at any auto paint store. The acid converts the rust to a protective coating.
But don't just cover the rust with bedliner stuff. The rust underneath it will just spread. You have to chemically stop it or completely remove the rust before you coat it, or it will just keep rusting under the coating no matter what you coat it with.
But after you remove the rust, you'd be better off using a two part epoxy primer/paint.

I've used the spray on undercoating on my bike's fenders with no problem but again kill the rust before you spray any paint or sealer.

steel wool and wax the hell out of it