Mark.... What does this mean: "The Cp will not work because of that is the corrosion phase inhibitor add value since it is closed environment. " ???,, -MJC

Mark.... I guess the best way to respond to your question would be to describe a properly configured flat-bottomed tank, mat and drainage system. To begin with, all rainwater must drain away from the tank. To allow rain to pool at the tank bottome is to ensure corrosion failure. Secondly, the most common configuration for tanks supported by a ringwall foundation is on an asphault mat. The tank bottom must be configured to drain away from the tank center and a thin bead of "sealant" must be applied around the tank bottom. Tanks installed in most states of the USA using an asphalt pad do not require a cathodic protection system. There is an excellent discussion of tank bottoms, pads and protection systems in the book "Aboveground Storage Tanks" by Phillip Myers. API also has "Recommended Practice 651," Cathodic Protection of Aboveground Storage Tanks, that may be helpfull to you This document is also helpful.. http://www.ecy.wa.gov/pubs/94195.pdf Please have the courtesy to complete this thread and et us know what your final solution is.... -MJC