New hot water pipes rusting and spauling on exterior

steve_25

I replaced the old delco (1915 era) oil hot water boiler in my home with a new burnham gas unit 4 years ago.  I used black iron pipes and connectors to repipe the connections.  I flushed the system and added an oxygen reducer.  I installed a new expansion tank (air bladder type) , air scoop, and auto fill valve.  The system works great.  However, the new black iron pipe  is rusting externally so bad that it is spauling.  what causes this?

photos if needed?

icesailor

Rusting Pipes:

Sens Photos.

Is the rusting and spalling on the outside?

Cheap pipe?

STEVE PAUL_3

New black iron pipes

Don't usually exhibit exterior rust and spauling after 4-years. I would look to see if there is some airborne contaminant such as chlorine or cleaning chemicals. I also question the use of an added oxygen reducer. I myself have never used or heard of this approach. What is the name of the additive and is it permitted by the terms of the manufacturers warranty

Charlie from wmass

When I have seen spalling

of the out side of pipe It is usually outside contaminants like have been mentioned or a very small leak at the threads that is drying before it drips. I usually see this at the circulator flanges on the headers.