Serpentine Mixed Metal Oxide Anode for Tank Bottom Corrosion
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Solution Overview
Problem
Conventional cathodic protection methods are ineffective for new and rebuilt ground storage tanks with secondary containment liners due to dielectric properties, requiring costly and short-lived galvanic anodes, and pose challenges in accessing and maintaining anodes beneath large tanks, leading to non-uniform current distribution and potential malfunctions.
Innovation Solution
A cathodic protection apparatus featuring a continuous mixed metal oxide ribbon anode shaped in a serpentine path within the compacted electrolytic backfill, connected by a feeding cable network to ensure uniform current distribution and extended design life, with redundant paths to maintain functionality in case of fractures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic ribbon anodes are installed in parallel lengths between the secondary containment liner and the tank bottom floor, then effective corrosion protection is achieved, but the system becomes costly for large diameter tanks due to large volume of anode material required
Solution Approach 1:
The patent combines multiple parallel anode ribbons into a single continuous serpentine anode structure. This merging approach maintains the distributed current distribution benefits of multiple anodes while reducing the total volume of anode material required, directly addressing the cost issue for large diameter tanks without sacrificing protection effectiveness
Solution Approach 2:
The patent employs a serpentine (curved) path configuration for the continuous anode ribbon instead of straight parallel segments. This curved layout allows the anode to efficiently cover large tank bottom areas with reduced material volume, optimizing the distribution of protective current across the entire tank bottom surface
2Reliability
If galvanic cathodic protection systems are used, then corrosion protection is effective, but the life of the system is limited and usually not commensurate with the design life of the storage tank
Solution Approach 1:
The patent transitions from galvanic anodes (which rely on sacrificial consumption) to a mixed metal oxide anode system that operates with controlled electrochemical reactions. This parameter change in the anode material composition and electrochemical behavior enables the system to achieve design lives matching or exceeding the storage tank's intended service life, eliminating the limited lifespan issue of galvanic systems
3Ease of operation
If the anode is not substantially uniformly spaced from the tank bottom, then installation flexibility is improved, but a near short occurs resulting in non-uniform distribution of protective current
Solution Approach 1:
The patent uses a flexible continuous ribbon anode that can be conformally installed along the tank bottom contour. This flexible film structure maintains substantially uniform spacing from the tank bottom through its inherent flexibility, ensuring uniform current distribution while allowing installation adaptability to various tank geometries and ground conditions
4Ease of manufacture
If the anode touches the tank bottom, then installation simplicity is improved, but a short occurs resulting in malfunction of the cathodic protection system
Solution Approach 1:
The patent introduces compacted electrolytic fill as an intermediary material between the continuous anode ribbon and the tank bottom. This mediator maintains the required electrical connection for cathodic protection while preventing direct contact that would cause a short circuit, thus preserving system functionality without complicating the installation process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides effective and uniform corrosion protection to the tank bottom with a long design life, minimizing maintenance and environmental risks while accommodating the constraints of large storage tanks.
Implementation Method 1
cathodic protection is a technique to control the corrosion of a metal surface by making that surface the cathode of an electrochemical cell
Implementation Method 2
the application of direct current to reverse the natural tendency for metals to return to their natural condition as metal oxides (rust)
Implementation Method 3
because of the dielectric properties of the secondary containment liner, conventional and widely accepted cathodic protection methods are not effective
Data Source
AI summary
In combination, a storage tank having a metal bottom, compacted electrolytic backfill below the tank bottom and a cathodic protection anode within the backfill below the tank bottom. The anode is in the form of a generally continuous ribbon that is shaped to follow a serpentine path corresponding generally in shape to the tank bottom. A feeding cable network is connected directly to the anode.