Cathodic protection is a technique used to prevent corrosion in metal structures, such as potable water tanks, which are typically made of carbon steel, making them susceptible to corrosion when exposed to water and oxygen.
Cathodic protection works by introducing a small electric current to the metal structure, which shifts the corrosion potential of the metal to a more negative level. This causes the metal to become anodic, which means that it is less likely to corrode. The electric current is typically provided by an external power source, such as a rectifier, and is transmitted to the metal structure through a series of electrodes or anodes.
There are two main types of cathodic protection used in potable water tanks: impressed current cathodic protection and sacrificial anode cathodic protection. Impressed current cathodic protection involves the use of an external power source to supply a constant electric current to the metal structure, while sacrificial anode cathodic protection involves the use of a more reactive metal, such as zinc or magnesium, that is attached to the metal structure and slowly corrodes over time, sacrificing itself to protect the steel from corrosion.
In potable water tanks, cathodic protection is an important technique for maintaining the structural integrity of the tank and ensuring that the water stored in the tank remains safe and uncontaminated. By preventing corrosion, cathodic protection helps to extend the lifespan of the tank and reduce the risk of leaks, which can lead to water loss and contamination.
Zinc primer, like Tnemec Series 94-H20, will also provide cathodic protection to potable water tanks. Zinc is a highly reactive metal, which means that it is more likely to corrode than steel. When a zinc primer is applied to a steel structure, it forms a sacrificial layer that corrodes in place of the steel, providing cathodic protection.
During the corrosion process, the zinc in the primer is oxidized and dissolved, releasing electrons that flow to the steel surface. This process shifts the corrosion potential of the steel to a more negative level, which makes it less likely to corrode. The result is a protective layer that helps to prevent corrosion and extend the life of the steel structure.
In addition to providing cathodic protection, zinc primers are also known for their excellent adhesion and corrosion resistance properties. They are widely used in a range of industrial and commercial applications, including marine, offshore, and bridge construction, as well as successfully in potable water tanks service for the last 25 years.
When used in tandem with standard cathodic protection systems, zinc primer can add value to the long term corrosion protection and extend years of service to the water tank. Further, using both systems in the same tank provides a belt and suspenders approach to corrosion protection by ensuring if either fail, the other will perform in its place. For more information or project profiles with zinc primer in potable water tanks, reach out to a High Performance Coating consultant.
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