Cathodic protection system for above-ground storage tank bottoms and

Abstract

The invention relates to a cathodic protection system for above-ground storage tanks having metal bottoms, either new or 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 material 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, maze or grid of interconnected titanium wires, or wires and ribbons or bars. A reticulate or open 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 wires may extend transversely of the bars or ribbon and are spot welded or mechanically connected on uniform centers to such bars or ribbons on diameters or major chords of a circular tank bottom. A low profile connection is provided between the bars or wires 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, straightening, bending, arranging and connecting the wires and ribbons on a compacted layer of electrolytic conductor on the liner. After the power feeds and reference cells are attached and routed to the external rectifier or test station, the insulator may be placed above the anode. Further compacted electrolytic material fills the openings in the insulator and the tank bottom is then constructed on the compacted material.