Direct assessment (DA) has been effectively used to evaluate the integrity of external
aboveground storage tank (AST) bottoms. When cathodic protection (CP) is applied to the
external surfaces of the AST bottoms, the corrosion rate can essentially be set to zero, per
American Petroleum Institute (API) 653, extending the tank internal inspection intervals up to 20
years (1). AST bottoms have a practical limited time when they can be assessed. DA of AST
bottoms will greatly improve the chances of detecting and preventing corrosion failures prior to
the next scheduled internal inspection.