PR620-23603-R01 Tank Foundation and Floor Designs and Best Practices for Improved Corrosion Control

Addressing the threat of corrosion on the floors of aboveground storage tanks (AST) has resulted in a variety of modifications in tank construction, inspection, and maintenance since the 1950s. Traditionally, cathodic protection (CP) systems have been used to provide soil side corrosion protection for ASTs built on-grade. Common industry practice was to build directly on soil or sand pads utilizing ring walls for the foundations. More recently, it is not uncommon to have ASTs that have been newly built or modified utilizing various other foundation designs and materials including designs incorporating multiple floors. In some cases, non-metallic liners have been installed. These may be between the floors within multi-bottom tanks and/or below the tank pads themselves.

These designs and practices have attributes that can affect the performance of traditional CP systems and monitoring techniques. Additionally, monitoring techniques may result in CP values that do not reflect the true levels of protection applied to the product containing tank floor, thereby masking potential issues, and failing to provide the intended benefit. This research examines the breadth of industry AST designs and modification practices including the applied corrosion control technique and leak detection practices. Inspection results will be reviewed to establish a performance based best practice for each of the newer common tank bottom and pad configurations utilized by member companies.

This information is intended for corrosion engineers, tank integrity personnel, inspectors, and facility operators, who can apply these results to improve CP system design, monitoring accuracy, and maintenance decision-making for AST floors.