ABSTRACT
The nature of the physical contact between the bottom plate of an above ground storage tank and the underlying foundation/soil varies considerably over the area of a tank bottom and from tank to tank. This may vary from direct electrolytic contact between the plate and moist underlying soil to void spaces between the plate and the soil due to floor buckling and/or soil settlement.
Cathodic protection is a proven corrosion mitigation technique where the target metal surface is in contact with a conductive electrolyte such as moist soil, but it will not be effective in void spaces where there is no electrolyte contact with the tank floor. Consequently, there is increasing application of vapor phase corrosion inhibitor injection beneath tank bottoms to ensure corrosion is mitigated in the void spaces.
The objective of this work was to evaluate the mutual compatibility and interactions between cathodic protection and a vapor phase corrosion inhibitor where applied together in a liquid-phase environment.
The work comprised of laboratory experiments to quantitatively evaluate the effects of a particular amine carboxylate based inhibitor and cathodic protection, when applied individually and jointly on an oxygen concentration corrosion macro-cell in a salt water solution.
The results indicate a beneficial synergistic effect between the particular inhibitor tested and cathodic protection, where the inhibitor enhances cathodic polarization to reduce cathodic protection current requirement, and cathodic protection reduction reaction appears to enhance the absorption & effectiveness of the inhibitor at the cathodic metal surface.
INTRODUCTION
The nature of the physical contact between the bottom plate of an above ground storage tank and the underlying foundation/soil varies considerably over the area of a tank bottom and from tank to tank. This may vary from direct electrolytic contact between the plate and moist underlying soil to void spaces between the plate and the soil due to floor buckling and/or soil settlement.
