A. Corresponding editor 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 time.
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.
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