Pipe Exterior Corrosion

NestOfSpies

Hi, What would cause corrosion like this on the exterior of our steam boiler pipes? There was asbestos insulation that we had abated a couple of years ago, but didn't re-insulate them. There is moisture in the room (efflorescence on some of the brick). Would there be anything that causes this from the inside? Any suggests on managing? Thanks in advance!

Jamie Hall

Concrete, portland cement, even some kinds of plaster stuck to the pipe can cause that. Coal dust, but that's unlikely.

Depending on how deep it is -- particularly the area in the first picture -- you may want to consider replacing the damaged pipe before you insulate them.

Which you should do (insulate) as soon as possible.

dopey27177

This pie cancer. Probably started with a pin hole in the pipe.

Pipe manufactures state that black pipe has a useful life of 20 years.

I for one would replace all the affected pipe before the heating season starts.

Jake

motoguy128

dopey27177 said:

This pie cancer. Probably started with a pin hole in the pipe.

Pipe manufactures state that black pipe has a useful life of 20 years.

I for one would replace all the affected pipe before the heating season starts.

Jake

Ha. My pipe is only 100 years past it’s useful life. Gee... I better replace it. Heck, someone Even welded two sections when they replaced the original boiler. When I’ve cut it apart, it looks great inside.

I‘m guessing a flaw/void in the metal that caused a pinhole leak, and system run at too high of pressure so it never “self sealed” and leaked into the insulation and expanded the corrosion.

The Steam Whisperer

The horizontals look like pinhole leaks on the bottom of the pipes.... usually caused by water collecting in the bottom of the pipes during the off cycle and creating carbonic acid that rapidly eats the pipe. I'd check the pitch on those pipes and replace the bad sections. For teh pipes near the boiler, again pinhole leaks for interior corrosion... again probably acidic condensate and/ or excessive make up water. The fresh make up water contains lots of oxygen and when it hits the hot condensate near the hartford loop the oxygen gets driven out of the water and is warmly greeted by the steel piping to create corrosion.

dopey27177

Motoguy

I did not say that he should replace all the pipe. I said replace the pipe in the affected areas.

Also I made the statement that pipe manufactures say the life of the pipe is twenty years, Just like humans, insurance actuaries say the average life of us is 78 years I beat that one already and I have a neighbor that is 106 years old.

So I think pipe can last a long time provided it lives in a good environment.

Jake

NestOfSpies

Thanks for taking the time to respond. So replace the pipes. Check. But sounds like pressure in the system is potentially too high or there is excessive makeup water. Would a fall maintenance/tuneup address those two issues?

Also, I can see some corrosion under the 'hood' of the boiler. I have been quoted about a day's worth of work to clean the exterior of the boiler (does not include flushing/interior work). That seem legit?

mattmia2

Before investing in dissembling the boiler to clean it, I would flood it above the water line and let it sit a couple hours to see if it is leaking.

Pressure too high isn't good, but a lot of fresh water entering the system is what causes excessive internal corrosion. If the pipes look like that and the exterior of the sections of the boiler have heavy scaling rust I would be concerned that it is corroded too.

As for the excessive make up water, you have to find the leaks. It could be rotted out return piping, it could be radiator or main vents that don't seal(which could be from excessive pressure), it could be valve packing leaking or other assorted leaks in the piping.

ChrisJ

The Steam Whisperer said:

The horizontals look like pinhole leaks on the bottom of the pipes.... usually caused by water collecting in the bottom of the pipes during the off cycle and creating carbonic acid that rapidly eats the pipe. I'd check the pitch on those pipes and replace the bad sections. For teh pipes near the boiler, again pinhole leaks for interior corrosion... again probably acidic condensate and/ or excessive make up water. The fresh make up water contains lots of oxygen and when it hits the hot condensate near the hartford loop the oxygen gets driven out of the water and is warmly greeted by the steel piping to create corrosion.

Is it common for improperly pitched run-outs to get pinholes?   I had one that looked like a perfect 1/8" hole drilled in it, I dinner l assumed that was someone's solution but maybe not?