PB Blaster won't hurt anything but rust. I've used it in place of KROIL to soak a bore.
I don't think it's the same as KROIL. It smells and feels different. However, they are comparable products.
I wouldn't leave either more than overnight though. When these products evaporate, they leave a tough coating behind (gasoline and WD40 do the same thing). If you want it to soak longer, make sure to resoak it every 24 hours at least.