reference cell shall be achieved over 95 percent of the area of the
structure. Adequate number of measurements shall be obtained over the
entire structure, pipe, tank, or other metallic component to verify and
record achievement of minus 850 millivolts "instant off." This
potential shall be obtained over 95 percent of the total metallic area
without the "instant off" potential exceeding 1200 millivolts.
b. A minimum polarization voltage shift of 100 millivolts as measured
between the underground component and a saturated copper-copper
sulphate reference electrode contacting the earth directly over the
underground component. This polarization voltage shift shall be
determined by interrupting the protective current and measuring the
polarization decay. When the protective current is interrupted, an
immediate voltage shift will occur. The voltage reading, after the
immediate shift, shall be used as the base reading from which to
measure polarization decay. Measurements achieving 100 millivolts
decay shall be made over 95 percent of the metallic surface being
protected.
c. For any metallic component, a minimum of four (4) measurements
shall be made using subparagraph a., above, and achieving the "instant
off" potential of minus 850 millivolts. Two (2) measurements shall be
made over the anodes and two (2) measurements shall be made at
different locations near the component and farthest away from the anode.
3.1.2
Aluminum
Aluminum underground component shall not be protected to a potential more
negative than minus 1200 millivolts, measured between the underground
component and a saturated copper-copper sulphate reference electrode
contacting the earth, directly over the metallic component. Resistance, if
required, shall be inserted in the anode circuit within the test station to
reduce the potential of the aluminum to a value which will not exceed a
potential more negative than minus 1200 millivolts. Voltage shift
criterion shall be a minimum negative polarization shift of 100 millivolts
measured between the metallic component and a saturated copper-copper
sulphate reference electrode contacting the earth, directly over the
metallic component. The polarization voltage shift shall be determined as
outlined for iron and steel.
3.1.3
Copper Piping
For copper piping, the following criteria shall apply: A minimum of 100
millivolts of cathodic polarization between the structure surface and a
stable reference electrode contacting the electrolyte. The polarization
voltage shift shall be determined as outlined for iron and steel.
3.2
ANODE STORAGE AND INSTALLATION
3.2.1
Anode Storage
Storage area for magnesium anodes will be designated by the Contracting
Officer. If anodes are not stored in a building, tarps or similar
protection should be used to protect anodes from inclement weather.
Packaged anodes, damaged as a result of improper handling or being exposed
to rain, shall be resacked by the Contractor and the required backfill
added.
SECTION 13110A
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