JANUARY 31 2003
operating at the same level as the last close-interval corrosion survey or corrosion
survey. This is a non-interrupted check and the potential measurements should be
compared to previous ON cycle potential measurements. The locations for the potential
measurements must be taken from the last close-interval corrosion survey, or corrosion
survey, whichever is most recent, to reasonably ensure that the current output of the
system is still being applied and is still sufficient.
Maintenance Intervals. The recommended period for conducting the
impressed current system check is within 60 days of the last close-interval survey,
corrosion survey, or impressed current system check. More frequent checks may be
required by public law or local regulations.
Note: Underground storage tank
CP rectifiers must
at a frequency not
exceeding 60 days to ensure compliance with regulations. Check with your state EPA
authorities as state regulations may be more stringent or may impose additional
Measure rectifier DC voltage and DC ampere outputs.
Ensure the DC ampere output of the rectifier meets the current (ampere)
requirement found on the last close-interval or corrosion survey. If necessary, adjust
the rectifier output, and measure outputs again. Repeat procedure as necessary.
Calculate the rectifier system circuit resistance by dividing the rectifier DC
output voltage by the rectifier DC output current. If the rectifier has more than one
circuit, calculate the resistance of each circuit.
Take S/E potential measurements at the locations of the three lowest and
three highest potential measurements identified in the most recent close-interval or
Compare the potential measurements to previous measurements at the
same locations and determine if changes have occurred. If potential measurements do
not satisfy criteria in Chapter 6, and the rectifier current output meets the current
requirement from the last survey, adjust or supplement the CP system as necessary.
Conduct a corrosion survey 30 days after adjustment or modification to the cathodic
GALVANIC ANODE CHECK. The galvanic anode system check is
conducted to determine its operational condition. It is normally conducted as part of the
close-interval survey, corrosion survey, or water tank calibration surveys described in
paragraphs 4-2, 4-3, and 4-4.