Cathodic protection system and method for above-ground storage tank

Abstract

The invention relates to a cathodic protection system for an above-ground storage tank having a metal bottom, both new and retrofitted bottoms. A leak containing dielectric safety membrane is spaced a short distance below and extends beneath the tank bottom generally parallel thereto forming a narrow envelope. Compacted electrolytic conductor is positioned between the membrane and the tank bottom supporting the tank bottom embedding a horizontally disposed cathodic protection anode, the anode being in the form of a matrix or grid of interconnected titanium bars and ribbons. A reticulate dielectric insulator may be embedded in the electrolytic conductor and positioned directly above the anode and such insulator is operable to keep any portion of the anode from contacting the tank bottom and to maintain a generally uniform spacing between the anode and tank bottom. The ribbons extend transversely of the bars and are spot welded on uniform centers to bars on diameters or major chords of a circular tank bottom. A low profile connection is provided between the bars and power feeds to a rectifier, and for large tank bottoms a multiplicity of such connections strategically spaced are provided. Similarly, a plurality of reference cells both in location and kind may be provided so there are redundant power feeds and reference cells. The anode is constructed by uncoiling, arranging and connecting the bars and ribbons on a compacted layer of electrolytic conductor on the liner. After the conductors are attached and routed to the external rectifier, the insulator may be placed above the anode grid. Further compacted electrolytic conductor fills the openings in the insulator.