Evaluation of Options for Failed AST Cathodic Protection Systems

What is the alternative when an interstitial type of cathodic protection system on an AST fails?  How is corrosion control to be provided?  Is it necessary?

 Proposal:

POND, in concert with the DLA-Energy Cathodic Protection CMP is conducting a demonstration of the different types of corrosion control methodologies available for ASTs with RPBs available subsequent to the failure of an impressed current cathodic protection system.  These include retrofit of the cathodic protection system and inhibitors.

Four identical vertical aboveground storage tanks located at NAS Pensacola, FL.  Within the past three years, the cathodic protection systems on two of the tanks have failed.  The system is still operational on two of the tanks.  The State of Florida DEP mandates that all aboveground storage tanks are provided with cathodic protection.  The DEP has also issued a finding that inhibitors may be used in lieu of cathodic protection, if properly monitored and maintained.  As stated, DLA-Energy has not used inhibitors for this type of application.  Given the mandate by the State, DESC must take some action to correct this deficiency.   This study uses the four tanks at Pensacola, as well as the two tanks in Niagara and one at Canon AFB, which have been retrofitted, to study the effective corrosion rates of tank bottoms under three different scenarios:

 Existing cathodic protection using the grid system;

1. Retrofit undertank cathodic protection system;
   1. Damp, cold environment (Niagara)
   2. Hot, dry environment (Canon)
2. Inhibitor corrosion control system;

 The corrosion rates on all tanks are being measured without any corrosion control applied for several months as a baseline.  The corrosion rates are then measured upon activation of the chosen corrosion control system, either inhibitor or retrofit cathodic protection.