Heavy corrosion on Copper

What causes this level of corrosion on these copper pipes? I don’t know that I’ve ever seen corrosion this bad I couldn’t find any galvanized connections anywhere some of the pipe is heavily green and almost flaking and others is absolutely black

It looks like the plumbers didn’t wipe the flux off all the way. You can see the discoloration where the joints were soldered. You may want to recommend putting some isolation tape between that steel pipe and the copper pipe.

Sometimes the environment just causes the copper pipe to become discolored.


Sulfur turns copper black. (sewer gases is one source). Also, as @mwilles mentioned, contact with steel, notably galvanized steel will contribute.


Yep. Looks like the steel pipe has some rust. Possible source of electrolysis, dissimilar metals in direct contact in a humid crawl…

The plumbers strap holding up the ABS is rusted also. definitely some moisture issues going on…


Often an indication of excess moisture in the area. Depending on the minerals in said water it can cause a lot of what is pictured. The cold pipes will typically be worse.

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Yeah from the looks of things, I’d say that crawlspace qualifies

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Chinese drywall will turn copper black.

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It defiantly lacked ventilation and had mold/mildew

Look up patina.