I have had good luck with PB Blaster as well...but...I've had better results with a product called Zoom Spout "RustBuster". This is the same company that makes the Zoom Spout Oiler containers which are great for oiling circulating pumps. I haven't seen it in awhile though. Also, there was a drawback to buying more containers that you could use up in a reasonable amount of time-evaporation. The product would disappear right off the shelf. Anyway, if you can find it-it's great product.
Ok...well I found the rustbuster I was referring to. It is available at Grainger here:
Apparently their version is made by LA-CO. I can testify to it's effectiveness on exactly the problem you are facing-carrier bolts, as well as a myriad of other institutional type applications like freeing up clean out covers that haven't been opened in 30 years or more.
It's good stuff...