electrode within plus or minus 0.010 volt when the sensing windows of the
two electrodes being compared are not more than 2 mm 1/6 inch apart but not
touching. Permanent reference electrodes not within this potential range
shall be removed from the construction site by the end of the day and
replaced at the contractor's expense. The testing provision shall also
apply to replacement reference electrodes as well.
3.1.4.2
Installation
Provide permanent reference electrodes at points in the tank [and riser
pipe] which shall monitor minimum and maximum tank[/riser]-to-water
potentials [and for automatic control system] [_____], and maintain
continuous immersion. Sensing windows of reference electrodes shall be
equidistant to and located within 25 mm one inch of the steel tank[/rise
pipe] surface and shall be fixed in position, preventing contact with tank
wall or appurtenances.
3.2
BOLTED AND RIVETED TANKS
Ensure electrical continuity of joining components.
3.3
GASEOUS EVOLUTION
Provide for possible evolution of gases from anode reaction and ventilation
requirements.
3.4
CRITERIA FOR CATHODIC PROTECTION
Conduct in accordance with [NACE RP0388] [NACE RP0196]. Criteria for
determining the adequacy of protection shall be selected by the orrosion
engineer as applicable.
3.4.1
Minimum
The criterion for cathodic protection shall be a negative potential of at
least 0.85 volt as measured between the tank[/riser pipe] and a
copper-copper sulfate reference electrode across the tank[/riser pipe] to
water interface. Determination of this potential shall be made with the
protective current applied to the tank [and riser] for a minimum of [24] [
] hours. Voltage drops must be considered for valid interpretation of
this voltage measurement. The method of voltage drop consideration shall
be identified by the Contractor's corrosion engineer and approved by the
Government corrosion engineer.
3.4.2
Maximum
The potential between a copper-copper sulfate reference electrode and the
tank[/riser pipe] at any point shall not be more negative than a negative
1.1 volt potential taken with the [electrode located within 25 mm one inch
of the tank[/riser pipe] surface but not touching it] [protective current
interrupted instantaneously or modulated] to minimize the voltage drop
effect.
3.5
FIELD QUALITY CONTROL
Field tests shall be witnessed by the Contracting Officer or his designated
representative. Advise the Contracting Officer [5] [_____] days prior to
performing each field test. Quality control for the cathodic protection
system shall consist of the following:
SECTION 13112N
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