Blacken copper in elec. panel and ac line

Found darkened copper at panel and a/c line in garage. Home was built in 93’. No other evidence of tainted drywall. Any ideas?

Did the water smell of sulfur

No, has city water. It may of one time had well. I checked 10 outlets, frige copper, plumbing in bath. All ok. And I know this house was built way before Chinese drywall hit. American made in garage attic lid.

Just guessing it could be from the high humidity in your area, How close to the ocean?

It is probably 15 miles inland. Home built in 93. Would well water outside sprinkler effect it? Panel on garage wall.

Chemicals stored near or under the panel box? or Cupirc Sufiate?

It could be Ronald , It seems it is only in the garage area . So most likely a environmental issue

Any way for sewer gasses to back up? Chemicals maybe for a pool or lawn fertilizer can do the same thing.

How about these water lines on tank in same garage? Tprv pipe different issue.

Russell, Home located in Waterways, good thought on chemicals.

Chlorine storage in garage will do it. Is there any rust on the electric panel?

Panel looks like new, no pool.

Funny that HWH only black on the cold side ? very interesting!

Does the black rub off on your hands and is it a dull flat black ?

I’d say possible Meth Lab in garage but it would turn all black not just the cold side unless that hot side just got replaced. Russ is right as well chemicals in garage but would turn all black not just cold. I have seen where the hot side only is black from condensation in a house with well and high sulfur content well water and A/C not running with windows open near well equipment.

No does not rub off. Maybe plumber rub his old work rag on it. Not that bad of neighborhood. Police Officers live next door on both sides.

The times that I have run into something like this, it has been in conjunction with an electric golf cart being parked in the garage and the golf cart is typically charged daily or frequently in the garage. Although my expierence has been limited to golf carts, other sulfuric acid based batteries frequently charged in an enclosed space may cause a similar situation. However, due to the sheer number of batteries in a golf cart and frequent in not daily charging, they are likely the worst culpert.

Thanks guys for the imput.

Yes, I have witnessed that scenario numerous times