Stains on the inside of my keg

I realized a couple weeks ago that one of my kegs has some linear brown stains on the inside. Looks like I probably stored it before it was completely dry. They are directly downward of the in and out holes. I cleaned it three times including a weeklong soak with PBW. However it looks the same.
Does anyone think this is a problem? I don’t think it is rust but it has to be CLEAN after a week long soak in for PBW right? I don’t want to have to buy new keg just cause I know that it doesn’t look pretty on the inside.

Could be beerstone, try using some Beer Line Cleaner.

You shouldn’t need to buy a new keg but you do want to remover the stains. Try a green scrubby tied to a long spoon after a hot PBW rinse. Beer line cleaner is a good suggestion too.

I would try scrubbing it with some Scotch-Brite No Scratch pads and Bar Keepers Friend.

I do the green scrubby zip tied to a long spoon thing semi regularly. Works great to scrub out tough stains on the bottom of the keg.

I ended up using barkeepers friend and it worked great. Looks like new. Thanks.