ELECTRO GALVANIC?

[Roach]

IT IS COMMON TO HAVE A DI-ELECTRIC UNION ON COPPER TO STEEL PIPE CONNECTIONS. IS THIS NECESSARY FOR DUCT CONNECTIONS AS WELL? MY UNDERSTANDING IS THAT THE WATER IS THE CATALYST FOR THE CORROSION, BUT CAN MOISTURE LADEN AIR PRODUCE SIMILAR RESULTS (I.E. COMMERCIAL DISHWASHER EXHAUST?)

 

[MintJulep]

Yes.

 

[tombmech]

Water can easily form an electrolyte that enhances the flow of electrons between two dissimilar materials, but the potential exists because of the difference in free electrons between the two metals. The obvious trait with pipe is that it's used for liquid transport anyway - most often water.

However, without insulating washers, the potential always exists except in a vacuum. You should not connect different metals together as ductwork - without an insulating gasket inbetween. Even then, special attention is needed for the attachment mechanism.

This is a very interesting site on corrosion that will give you more info than you'd ever want:
Corrosion Doctors - Galvanic Corrosion

 

[Roach]

THANKS FOR THE INPUT. I WAS SECOND GUESSING MYSELF, BUT IT LOOKS LIKE I MADE THE RIGHT DECISION IN ISOLATING THE TWO DUCTS.

BTW TOMBMECH: THE LINK YOU POSTED IS VERY INFORMATIVE

THANKS AGAIN