Rust In Keg

I have a corny with 3 small rust spots that total would be about the size of a quarter. I am new to kegging and was wondering if anyone has experience with this. When I initially got the keg about a week ago some of the rust wiped off with a paper towel but I have been soaking it now in oxyclean for a week and the rust looks unchanged but will not wipe out now.

I don't feel confident putting beer in it the way it is. I can take it back but I'm not sure if this is necessary if it's not a problem. Opinions?

BarKeepers friend for rust on SS works well, HOWEVER I would take it back if it is easy to do. You really don't know how far into the SS the rust has gone and why take a chance.