On Monday, 11 March 2019 17:37:33 UTC, misterroy wrote:
What could have caused the heating pipe to corrode so badly that it failed? It was next to an external wall and lagged. The are a couple of lengths of the pipe lying outside the building unused for the same 6 years, other than the threaded ends, they look new.
image https://drive.google.com/open?id=1o8...cqBdRGYatmQb6R

If it is attached to copper pipe elsewhere in the system, zinc and copper are perfect for galvanic action.
Depends too on the quality of the water in the system. Inhibitors are available.