PR644-183611-R01 Vapor Corrosion Inhibitors Effectiveness for Tank Bottom Plate Corrosion Control – Phase 2

Soil-side corrosion control is a major challenge for Aboveground Storage Tank (AST) operators. Vapor Corrosion Inhibitors (VCIs) are increasingly being used as an additional corrosion control mitigation tool. A PRCI-sponsored Phase 1 study established baseline performance and evaluated monitoring methods for the VCIs. One focus of this study included VCIs’ performance comparison with effective cathodic protection (CP) systems. The investigation concluded that VCIs’ corrosion mitigation performance is equivalent to that of an effective CP system. This study also evaluated tank bottom corrosion monitoring tools, investigated VCIs’ migration behavior, determined VCIs performance in the presence of high levels of chlorides and bacterial activity, and evaluated VCI delivery methods considering tank pad conditions. This study concluded that mass-loss coupons installed a few inches below the tank bottom generally agree with tank floor inspection data, thus either bonded or unbonded mass-loss coupons could be used as one of the corrosion monitoring tools to assess tank pad corrosivity. The experimental work on VCI migration showed that VCIs migrate quickly through a sand environment. Thus, VCIs should provide corrosion mitigation coverage to an AST tank bottom soon after their delivery. The experimental work also showed that VCI performance is robust and not compromised in the presence of either high chloride levels or bacterial activity. Finally, the through-the-floor VCI delivery method is more efficient compared to the through-the-sandpad when tank pad corrosivity is elevated.

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