Abstract
The close anode ground bed cathodic protection (CP) system design for the Aboveground Storage Tank (AST) bottoms uses the area of influence surrounding each anode ground bed, in contributory area design, to provide adequate CP. The area of influence surrounding each anode ground bed, mainly depends on the adopted CP criteria, and is greatly affected by the changing electrolyte resistivities of the AST tank pads and the distance between the anode and the structure. Accommodating for changing electrical properties is a standard requirement for CP designs and the spacing of anodes is adjusted to get proper current distribution coverage. In case of a deficient CP design, where the design parameters are not cautiously considered or when the field parameters change considerably from the design assumptions, CP will be inadequate.
In this paper, the CP current distribution with changing resistivities and the area of influence required to meet effective CP criteria, is studied. The results indicate that the tank pad electrolyte resistivity plays a significant role in achieving uniform CP current distribution. The paper also explores the use of Vapor Corrosion Inhibitor (VCI) and its effect on electrolyte resistivity and the resulting CP current distribution.
