Built in the 50's and on heating pipes I would say with confidence it is asbestos. Highly recommend contacting a remediation company which will recommend the best course of action. The sealing/wrapping they do is 100% effective and affordable it also will not hinder your future chances of selling the home (if this is an important factor). Asbestos sealed by a licensed remediation company (Licensed is CRITICAL) will pass FHA guidelines etc.