- Q.If a copper water pipe is in
contact with the metal sheathing of BX cable, can that
contact cause the cable to corrode?
Paul Fisette responds: Yes. The flexible
sheathing on BX or AC (armored cable) is made of
aluminum or galvanized steel, and contact with a
copper water pipe can cause it to corrode over
Galvanic corrosion occurs when dissimilar metals
are placed close together in the presence of an
electrolyte like water. In this case, condensation
on the pipe functions as the electrolyte. The zinc
coating or aluminum (anode) is sacrificed to the
copper (cathode), which remains intact.
There is perhaps a more important concern than
corrosion: Such contact can be dangerous. The metal
sheathing on the cable functions as the exclusive
grounding path for the wire. In case of a short or
ground fault, a pipe touching the cable could be
charged and become a hazard.