How do I connect two pieces of conduit that are different metals?

Connecting Dissimilar Conduit


I have just started on a job and the specification states PVC-coated galvanized rigid conduit should be used below grade, but from there I have to use rigid aluminum conduit. How do I safely connect the two dissimilar metals? The spec also states to keep the aluminum isolated by using plastic sleeves or plastic-coated hangers.


Plastic sleeves or plastic-coated hangers are often used as isolation options to prevent corrosion due to dissimilar metals. An additional option, according to Article 344.14 of the NEC, is to use galvanized couplings to make this transition where not subject to severe corrosive influences. Thread compound such as STL8 at the joints where dissimilar metals are present is also recommended.