Dissolved Cable

[Jim Katen]

I've never seen this before. The MC cable was secured to a basement wall with some very attractive metallic & velvet wallpaper sandwiched between the two. The cable sheath just dissolved into a white crust. My best guess is that this is the result of galvanic corrosion, where the metal in the wallpaper acted as a cathode to the cable sheath, which acted as an anode. Any other ideas? 

 

[Marc]

Is that cable clamp touching the panel enclosure?  Energized sheathing from leakage on the load side?

[BADAIR]

other factors causing the rust & staining makes me suspicious of just galvanic corrosion

i've seen similar evaporating MC in commercial from rats or mice using the cable as their highways & byways 

their urine isn't metallic friendly

 

Edited September 10, 2020 by BADAIR

[Jim Katen]

The whole area was very damp. You can see a bloom of green mold at the upper left side of the 1st picture. However, I saw nothing to suggest any other corrosive substances. 

I'm not sure why leakage of current would matter? 

[Marc]

4 hours ago, Jim Katen said:

The whole area was very damp. You can see a bloom of green mold at the upper left side of the 1st picture. However, I saw nothing to suggest any other corrosive substances. 

I'm not sure why leakage of current would matter? 

You can use a wet cell to produce electricity or you can use electricity to promote galvanic action. I know its alternating current but it can promote galvanic action half the time.

Edited September 11, 2020 by Marc

[John Kogel]

Maybe having a charge on the conduit would discourage the rats. I'm with Barry, piles of turds on top of the panel box, no doubt. I can smell that place from here. 🤓

[Jim Katen]

Actually, the place was relatively rodent free (for Portland, which should really be called "the city of rats.") 

I'm certain that urine was not at play here.