1997 Volume 46 Issue 6 Pages 352-356
Legally mandated inspections for fuel strage tanks resulted in detecting many cases of corrosion both inside and outside surface on the bottom plates of tank. Superior coating materials were developed to prevent corrosion on the inside surface, however there were no corrosion prevention technologies for the outside surface. It is required to develop a technology to measure outside surface corrosion rate and the authors developed a new type two-frequency corrosion monitor. It was used to conduct long term monitoring of two in-service fuel storage tank bottom plates. One was submitted to zinc plates on the circumference of the outside surface for cathodic protection, and the second was not. Nine-years and two-months monitoring for the non-protected tank indicated that the maximum value of the corrosion rate on the circumference was two orders of magnitude larger than that at the center. The estimated corrosion rate led to considering tank reconditioning within four to five years. Four-years and six-months monitoring of the protected tank showed few indications for the necessity to recondition the tank due to the corrosion prevention effect.
