Plumbers? Copper Turning Black...Oxidation?

[FoieGrasIsEvil]

All-

I run a car wash in the Cincinnati area. Within the last year or so, I’ve noticed our copper piping turning steadily blacker and blacker, to the point now where it’s completely black.

I did some googling and tried to find a cause. The common theme seems to be some type of sulfur exposure that causes this, similar, I think, to that situation that happened in Florida after that big hurricane cause a slew of home rebuilding and contractors were using that Chinese drywall that was fouling up anything copper in the homes, piping, wiring, etc.

Problem is, we don’t have any drywall in our equipment room, it’s a concrete structure.

I also saw references to the possibility that there could somehow be a current going (into? through?) the pipes, but I already tested them out with a multimeter and I’m not detecting any voltage or amperage.

A couple points:

The blackness on the pipes isn’t some kind of residue. You can rub your hands on it and it doesn’t come off.

We do have a water reclamation system, but the copper piping for it is more bluish than black, and the fresh water piping is completely separate anyway.

The pipes seem the blackest above our hot water boiler, which makes me wonder if it’s a temperature issue as well. Thing is, we hardly ever use that boiler…only in the coldest winter days.

I’m trying to think what this could be. We have a massive water softening system, but I can’t imagine that being an issue. We also store 55 gal barrels of low and high Ph soaps, wheel cleaners, etc back in that room…but when they are hooked up, the chemicals are sent through a solenoid/valve system that sends the mixture out into the tunnel, and I have no reason to believe that it’s backflowing into the main fresh water supply. Besides, the low Ph soaps would corrode the copper from the inside, not the outside.

Any ideas at all what could be causing this? I’m at a loss.

[johnpost]

@FoieGrasIsEvil

I run a car wash in the Cincinnati area. Within the last year or so, I’ve noticed our copper piping turning steadily blacker and blacker, to the point now where it’s completely black.

Any ideas at all what could be causing this? I’m at a loss.

copper readily oxidizes. copper will go to brown, black and green oxides. the brown oxide is a protective oxide layer (similar to aluminum with a white oxide) the black and green oxides are destructive oxides (similar to iron with rust). the brown oxide can get very dense and under some lighting look very dark and hard to tell it from black, though the black oxide is very black.

the black and green oxides will come off fairly easy with rubbing (cloth). the brown will come off with abrasive rubbing (sandpaper).

if the copper can dry out the brown oxide will occur and is good to have. if the copper stays wet or might have certain chemicals in contact the oxide can be the black and go to the green. heat will cause any oxidation to occur faster.

[FoieGrasIsEvil]

@johnpost

copper readily oxidizes. copper will go to brown, black and green oxides. the brown oxide is a protective oxide layer (similar to aluminum with a white oxide) the black and green oxides are destructive oxides (similar to iron with rust). the brown oxide can get very dense and under some lighting look very dark and hard to tell it from black, though the black oxide is very black.

the black and green oxides will come off fairly easy with rubbing (cloth). the brown will come off with abrasive rubbing (sandpaper).

if the copper can dry out the brown oxide will occur and is good to have. if the copper stays wet or might have certain chemicals in contact the oxide can be the black and go to the green. heat will cause any oxidation to occur faster.

It does get extremely hot inside the equipment room in the Summer months, as it isn’t ventilated at all. I’m talking 120-130 degrees on the very hottest days. The pipes sweat like crazy.

I just talked to someone and he suggested that maybe there’s a dry drain trap (or possibly even our water reclaim system, which has a grate-covered opening in the room) that is issuing “sewer gas” into the room, causing the reaction.

Thoughts?