Photo Gallery B8:  Steel to Steel Electrolysis

Electrolysis can occur at steel pipe which is supported by structural steel depending upon the difference between its ground potential and the ground potential of the building itself.  This is a relatively rare event which typically occurs hidden from view at the contact surface of only one metal side.  A different but more common issue occurs when copper pipe is support by a steel pipe hanger.

It is most common for pipe where its outer surface is wet for any reason, given that the surface moisture then becomes an electrolyte favoring the movement of electrons.  For outdoor located pipe supported by either pedestal or pipe hanger, water and weathering may also play a role; accelerating the localized loss.

Steel to steel electrolysis has been identified in the immediate vicinity of the pipe hangers of fire sprinkler systems and where condenser water lines are supported by floor mounted pedestals or pipe hangers from some other building grounded support, such as the cooling tower.  Although different types of plastic or different electrical isolators exist, they are rarely if ever installed for HVAC applications.  Improper grounding is a common source of the problem, but extremely difficult to diagnose.

Other related issue are where computer room power distribution units, PDUs, have been found to shed voltage to ground – thereby producing an impact to either steel or copper pipe.  In one very difficult to diagnose case, the main supply of domestic water to a housing unit through 4 in. PVC, but with all grounding attached to the copper pipe within the building and no grounding rod, no true ground existed.  Instead, shed voltage moved through the copper pipe through other pathways; producing widespread pinhole failures at contact points.

When failure occurs, its location at the contact point between pipe and support adds further difficulty in effecting emergency repairs.