AST Product-Side Bottom Protection – ZERUST® ReCAST-PSB

AST Protection For Tank Bottom Internal Surface

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Multistage ReCAST-PSB solution deployed on the internal surface of an AST bottom.

Initially, as the aqueous solution is not abundant, and the primary protection comes from the inhibitor.

As aqueous solution sediment increases, the cathodic protection (CP) begins to function, continuously lowering the use of the inhibitors.

Industry Problem:

Aqueous solution sediments (e.g. water and sludge mixed with different salts and sulphur compounds) accumulating at the bottom of Aboveground Storage Tanks (ASTs) used for petroleum products cause significant corrosion damage. Tank operators have to periodically stop tank operations in order for repairs, or in some instances replace the entire bottom. The stoppage time can come within the first few years of a tank’s life (2 to 4 years), or at scheduled inspection intervals (6 to 10 years as per relevant API 650 guidelines), resulting in costly production losses and other negative impacts.

Our Solution:

NTIC has developed a comprehensive corrosion protection solution combining its proprietary combination of chemical inhibitors and optimized sacrificial cathodic protection (CP) systems. As consistency of aqueous sediment at the bottom of the tank changes, the Zerust® ReCAST-PSB system maintains its high level of protection efficiency.

The Zerust® ReCAST-PSB system has been developed to work in such aggressive internal corrosion environments as illustrated by the key parameters below:

Critical Parameter	Range of Values
Temperature, °C	Up to 55
pH, S.U.	4 - 8
Inorganic Salts, g/L	4 – 250*
H2S and SO2 , ppm	Up to 1,000
O2, %	Up to 10

*Summary concentration of NaCl, MgCl2, CaCl2, NaHCO3, Na2SO4

Actual pitting corrosion pictures taken at a client’s site:

CORROSION HOLES IN THE AST BOTTOM

CORROSION DAMAGE ON THE UPPER BOTTOM PLATES OF THE ABOVEGROUND STORAGE TANK