Due to the recent regulatory requirements of using double containment for hazardous liquid storage tanks, grid type impressed current cathodic protection systems for the protection of bottom undersides, are a relatively new phenomenon. Design details of such a system is discussed and the problems encountered during the commissioning and operation of the system for a large tank farm in our company are described. Trouble-shooting and testing methodology including failed reference electrodes, “IR” drop error in potential measurements and imbalance in current and potential distribution with recommended corrective action are also provided. The conclusions include the
preference to use stepless rectifier units for continuous control, a perforated tube installed between the liner and tank bottom for test reference electrode insertion, use of 100 millivolt potential decay criterion for protection and an average cathodic protection current density in the range of...
Key words : Above ground storage tanks, secondary containment, HDPE liner, cathodic protection, impressed current, grid system, mixed metal oxide coated titanium anode, 100 millivolt potential decay.