Innovative Strategies for Soil-Side Corrosion Mitigation on Tank Floor Bottoms
Mitigating soil-side corrosion on tank floor bottoms is an important aspect of ensuring the integrity and longevity of storage tanks. Soil-side corrosion occurs when the tank bed and soil surrounding the tank, interacts with the tank floor, leading to accelerated metal loss on the tank floor from the soil-side.
Here are some measures commonly employed to mitigate soil-side corrosion on tank floor bottoms:
Vapor phase Corrosion Inhibitors (VpCIs)
There is a growing interest in the industry to introduce CorroLogic™ material beneath existing and new tank bottoms as an economic and effective solution to mitigate soil-side corrosion and supplement the performance of existing corrosion protection systems.
CorroLogic™ material is a Vapor phase Corrosion Inhibitor (VpCI®) that acts to reduce soil-side corrosion by a combination of volatilization from the VpCI® media, vapor transport in the headspace between floor plates and the tank pad atmosphere, and adsorption onto surfaces in the space. The inhibition mechanism involved includes adsorption, dissociation, and hydrophobic effects on metal surfaces, where the rate of soil-side corrosion of bottom plate surfaces is thereby inhibited. CorroLogic™ material comes in different forms to fit different application methods in protecting storage tank bottom plates. It comes in powder form (CorroLogic™ Powder) and can be delivered by fogging application through the tank floor while it is out of service.
Visco-elastic corrosion protection system for Chime Area
Because of daily and seasonal weather fluctuations, condensation and moisture can accumulate at the chime of the tank and seep under the base of the tank through the gaps between the annular plates and tank foundation. Such gaps also allow for the ingress of air born chlorides, oxygen and other corrosive species leading to the acceleration of oxygen concentration cells that lead to pitting corrosion, especially at the periphery of the tank.
The proposed chime area seal system is based upon the use of a STOPAQ visco-elastic sealant in combination with a visco-elastic wrapping band and UV topcoat. Since the floor plate of a tank is constantly moving during the filling and emptying process, flexibility and aggressive adhesion is of utmost importance. It is equally important for the seal system to exhibit good resistance to a wide range of chemicals and heat and in addition provide excellent corrosion protection, therefore offering a long-term solution.
Besides the physical barrier role the seal system plays, it encapsulates the circumference of the tank base and creates the required enclosure for the vapor phase corrosion inhibitors and ensure its long-term effect.
Compatibility with Cathodic Protection
Several studies and tests have been performed to verify the compatibility of VpCI® and CP. It has been confirmed that VpCI® is compatible with CP and when used in combination, it lowers the usage of the electric power necessary for the cathodic protection. The results indicate a beneficial synergistic effect between VpCI® and cathodic protection, where the inhibitor enhances cathodic polarization to reduce cathodic protection current requirement, and cathodic protection reduction reaction appears to enhance the absorption & effectiveness of the inhibitor at the cathodic metal surface.
Proper Soil Selection
Choosing the right soil for tank installation is crucial in preventing soil-side corrosion. Soil with low corrosivity, such as non-corrosive or non-aggressive soils, should be selected. Conducting soil tests and consulting with geo-technical experts can help determine the suitability of the soil for tank installation.
Proper drainage around the tank is essential to prevent the accumulation of water or moisture that can accelerate corrosion. The tank should be installed on a well-drained surface, and proper slope should be provided to direct water away from the tank bottom.
Regular Inspections and Maintenance
Regular inspections of the tank floor, including visual inspections and non-destructive testing methods like ultrasonic testing, can help identify early signs of corrosion. Any damage or corrosion should be promptly repaired to prevent further deterioration.
Consulting with experienced, well-respected corrosion engineers and experts in tank design and maintenance can provide more tailored guidance for mitigating soil-side corrosion on tank floor bottoms.
To learn more about soil-side corrosion on tank floor bottoms from one of our experienced corrosion engineers, contact us through the contact form on this website or by sending us an email at firstname.lastname@example.org.