Determining Vapor Corrosion Inhibitor Dispersion Range Under the Tank Pad Conditions

Abstract Vapor Corrosion Inhibitors (VCIs) are increasingly being used as a corrosion control measure for soil-side corrosion of Aboveground Storage Tanks (ASTs). VCIs are primarily applied to the tank bottoms using one of the following two delivery methods: (i) through-the-sandpad, and (ii) through-the-floor. Through-the-sandpad delivery is employed for tanks that are in-service, while through-the-floor delivery is used for out-of-service tanks. Access to the tank bottom is relatively uninhibited for the out-of-service tanks, and therefore, VCIs applied using the through-the-floor delivery method are expected to provide coverage to the entire bottom plate. However, for in-service tanks using the through-the-sandpad delivery method, VCIs are injected through the multiple injection ports that are at discrete locations along the ring-wall (single bottom) or dead-shell (double bottom). After VCIs are injected, it is expected that VCIs would migrate via various mechanisms such as molecular diffusion, volatilization, convection, etc., and provide corrosion mitigation coverage throughout the bottom plate. Large-scale experiments were conducted to determine the VCI dispersion range in an actual tank-like conditions. Experimental data and results are presented to establish the dispersion range of the VCIs.