Soil side corrosion of surface storage tanks can be a serious problem. In many industries the life of the tank is limited by external corrosion of the tank bottom. Cathodic protection (CP) is a cost effective technique used to eliminate soil side corrosion and hence can indefinitely extend the life of the tank bottom and significantly increase the intervals between internal inspections as recommended in API 653.
Many owners are now installing secondary containment when constructing new tankage. Most of these containment liners are fabricated from non-conductive materials that may prevent the application of cathodic protection unless specific components are installed concurrently with tank fabrication.
This paper will examine the corrosion mechanisms of tank bottoms as well as the various designs of CP systems with and without secondary’ containment.