Questionable Mash Tun Seal

Hey all,
About six months ago I moved to the oppressive state of Alabama for flight school, where homebrewing was illegal until about a week ago. I decided to get my equipment out and see what kind of shape everything was in and, with the exception of my mash tun, everything looked pretty good. The seal on the inside is oxidized and rusted over, as shown in the attached picture. Is it safe to mash in it or should i try to get it off? The problem is that I'm not sure that I could get if off if I wanted to. What do you think?

I am thinking I would soak it in a little vinegar then rinse the crap out of it. Kind of weird for me to say since I just knock the bigger chunks out of mine but rusty looking stuff I would not like in my beer