Volatile Corrosion Inhibitors for Above Ground Storage Tank Bottom Plate Soil Side Corrosion Protection
Kamal Mohamed El Sayed Moussa
Principal Engineer Corrosion and metallurgy. SME in Corrosion, Cathodic Protection, Protective Coating, Water Chemical Treatment and Material (Selection, Testing & performance evaluation)
General
Soil-side corrosion of the above ground storage tank bottom plates?is a major concern even for tanks provided with Active Cathodic Protection System .
Above ground storage tanks are typically constructed on concrete ring walls or sometimes by compacted dense gravel aggregate API 651.
The tank bottoms are typically bare steel (or even coated with coating damages/burnet at plate seam welds) and supported by a sand pad of varying thickness.
The sand is expected to be in accordance with API 6512 or operator-developed standards.
Old design ,tanks constructed on asphalt lined concrete without cathodic protection system and cathodic protection can not be provided without tank bottom plate replacement/removal
Most above ground storage tanks are provided with active cathodic protection (CP) systems to protect the tank bottoms.
Industry experience indicated that soil-side corrosion could occur at sever rates and CP alone may be insufficient. This is because CP could partially or completely fail, or CP may not reach the entire surface of the plate—as in the case of local soil settlement and associated depressions which could form due to repeated flexing of the bottom plates.
In addition, a tank without a CP system could experience severe corrosion depending on the pad conditions API 651.
VCIs were found to be effective in mitigating pitting of Carbone steel exposed to corrosive sand when recommended dosages were used.
VCIs significantly reduced the tendency of pitting, but pitting rates were not mitigated to the extent specified in NACE SP0193 and NACE SP0169 for demonstrating adequate CP.
use of VCIs could provide protection, and extend the metal service life , for the tanks without CP or where CP systems have either failed or degenerated.
Electric resistance probes, designed to measure the surface average corrosion rate, can be used to monitor both the plate corrosion rate and efficacy of VCIs.
VCIs are compatible with ICCP systems, but changes in native potentials of carbon steel must be considered when using VCIs in combination with CP.
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This proof-of-concept of the VCI technology,
CASE STUDY
Effect of vapor phase corrosion inhibitor on Carbone steel in tape water
Inspection and Corrosion Section Head (oil and Gas Sector)
3 年Non traditional mitigation technique to avoid bottom plate soil corrosion, is going well and will be effective tool against the common threats.
Sales Manager -Qatar at DNV -Inspection
3 年Bravo Kamal This Article is fruitful
Corrosion Div. Superintendent. at Akakus Oil Ops.
3 年It's very interesting tool, we are in process of introducing it for one of our replaced bottom plates tank.
Operations Manager at Sogec (Specialized Oil & Gas Engineering Co.)
3 年Good one Kamal ????????
VPCI is a newly technology being recently implemented since last decade with good results..more and more tanks will get it…