JANUARY 31 2003
DC. If a structure is copper or steel in concrete under normal conditions, the potential
should be between approximately -0.20 volts DC and -0.30 volts DC; and if a structure
is galvanized (zinc-coated), the potential should be between approximately -0.80 volts
DC and -1.05 volts DC.
If the two potential measurements are not significantly different (under 25
mV), the two structures may be shorted and additional testing is required.
a) Install a temporary local cathodic protection system to apply current to one
of the structures (paragraph 7-10) to be installed where the current should distribute
equally to both structures.
b) Repeat the potential measurement of both structures. If the potential of
the structure without the current being applied to it remains approximately the same or
changes in a positive direction (less negative) when the potential of the structure with
current applied changes in a negative direction, they are not shorted. If both potential
measurements change more negative as current is increased, the two structures are