Vapor Corrosion Inhibitors for Storage Tanks

API Technical Report 655, First Edition, April 2021

Purpose of API TR 655

API TR 655 has been published by the American Petroleum Institute (API) to provide guidance on using Vapor Corrosion Inhibitors (VCIs) to protect the soil-side of storage tank bottoms from corrosion.

VCI Chemistry

VCIs use several chemical mechanisms to reduce corrosion rates on metal surfaces in enclosed environments. The effectiveness depends on both the chemical composition and the delivery method. Learn more about how VCIs work here.

Guidance for VCI Use

The technical report provides detailed information on applying VCIs for corrosion protection of the Soil Side Bottom (SSB) of Aboveground Storage Tanks (ASTs). It includes guidance for both in-service and out-of-service tanks, accommodating different civil foundation designs.

VCI and CP Compatibility

While the DOT-PHMSA does not currently allow the use of VCIs without Cathodic Protection (CP) for "break-out" tanks, most non-regulated tanks may use VCI alone or in combination with CP. This approach is discussed in API 651.

VCIs in Company Specifications

Have you updated your company specifications to include VCIs for tank bottom protection? If not, contact us and our team of corrosion experts will help you design a customized protection plan.

Purchase API TR 655

To purchase a copy of API TR 655, visit the API Publications Store. It is also available through other standards document providers.

For a deeper dive into application methods, monitoring, and VCI + CP synergy, read our full article here.