Unusual Copper Pipe Corrosion

[Dan1990]

Hi, I had some of the floorboards up today and I spotted a short section of copper pipe for the heating that is extremely corroded. The copper is flaking away in layers and looks like it should have burst long ago. Not the usual green residue.

Does anyone know what may have caused the corrosion? The pipework in the house is old, but I have not seen problems elsewhere.

I attach a couple of photos showing the top and underside. The adjacent pipe has had a rub with some wire wool to remove the tarnish and it looks to be unaffected.

 

[zzzjim]

Try a magnet (is it even copper ?)

 

[Fos]

Looks like a protective coating / paint flaking away rather than copper

 

[Dan1990]

It’s definitely copper. I’ve attached another photo to show the surrounding pipework.

 

[snowhead]

Thats calcium out of the water that's flaking.

There's been a small leak, most likely a pinhole, probably further along that pipe than is exposed and it's run back to where you can see it.
It may not be the heating pipe that's leaking, it could be another close to it.

 

[Dan1990]

That’s interesting. Where the pipe disappears from view it goes up vertically in a box section to the upstairs. It’s possible that water has ran down the pipe and accumulated on the horizontal section. I might put some vinegar on it later and see if it reacts.

 

[iljoosk]

Looks like a protective coating

 

[oz-plumber]

I have seen something similar years ago.
It was a stray electric current that corroded the copper.
There was less than 12 volts, but it caused major damage

It may be worth investigating this route

 

[Rob Foster]

Whatever it is, I like the electro
reaction or protective coating notion. I would scratch it back and see if its still solid. If not rip it out quick time. But deffo check any milli amp readings on it to see if there is a electric leak. it may be like a sacraficial
anode on a canal barge which burns away rather than the whole hull getting thinner
Rob Foster aka centralheatking

 

[Dan1990]

I can confirm it is calcium on the pipe as it started fizzing when I poured vinegar on it. I left a rag soaked in vinegar wrapped around the pipe and when I came home today quite a bit of it had softened and broken down to a white powder.

Thanks Snowhead for the advice, I never imagined the flakes could be calcium deposits.

 

[snowhead]

Did you look for a leak anywhere else?
It could be a soldered joint that's now sealed with calcium.

 

[Dan1990]

I think I’ve found the source of the original leak upstairs. I lifted the floorboards this evening above where the pipe enters the ceiling void and I can see where a section of plasterboard has been replaced and a section of new pipe. I guess someone had a leak and did not immediately notice.

The central heating is unvented and maintains its pressure so I’m pretty sure it’s leak free at the moment.