Corrosion is an ever-present issue with water storage tanks that must be addressed as part of good tank maintenance.
Although it is impossible to stop all corrosion as tanks age, tank engineers are continuously coming up with newer and better ways to protect them with anti-corrosive coatings and other means.
The preeminent way to minimize this slow destruction of expensive water tanks for potable drinking water is to first understand how and why it happens as described in this first of a 2-part article on corrosion and what water tank maintenance services should be done to slow this natural process.
What Are the Causes of Water Storage Tank Corrosion?
Before water tank engineers can deal with the question of protecting these vessels from corrosion, it is essential to understand what causes corrosion in the first place.
Slow decomposition is a natural act that nearly every material suffers from, caused by the laws of chemistry.
In terms of metal, it happens when three things are present: metal, oxygen, and a third material referred to simply as “electrolyte.”
These elements react with each other over time as the natural electrical iconic current is passed between them, corrosion being the end result.
Corrosion also occurs due to the changing of the state of the metal and making it more susceptible to chemical reaction, such as when it is melted to turn it into something else like a water storage tank.
Tank interiors are almost constantly exposed to the corrosive process, while tank exteriors may not be based on the atmospheric conditions.
Taking all of this into consideration, the main goal when developing protective coatings and storage tank service procedures to protect the metal is finding ways to lessen or prevent the natural chemical reaction from taking place.
How Can Corrosion to Water Storage Tanks Be Prevented?
Protective coatings offer the best protection against corrosion when correctly applied during water storage tank production.
Yet the need for protection differs on the inside and the outside of the vessel, so different coatings must be used.
Water tank engineers find that it is possible to reduce or eliminate exterior corrosion with the right coating when the environment is such that the coating prevents the reaction and the passage of ions because the electrolyte is not always present.
The interior of these containers must be handled differently since the metal is in constant contact with the water, meaning corrosion is constant unless the transfer of ions between the metal and the water can be prevented.
- The first line of protection for tank interiors is correctly applied coatings that are well maintained to remain free from defects.
- The second line of protection used by water tank storage services is cathode protection, an electrical method that prevents the metal from reacting with the electrolytes in the vessel.
This technique works by applying a low current to anodes inserted into the container which attract the electrolytes, preventing them from acting on the walls of the tank as much.
Combined with a durable metal coating, this is proving to be the most effective method for maintaining water storage tank interiors.
It has even been shown to triple the time between new coating applications, saving tank owners greatly in maintenance, shutdown, and coating costs.
Protecting Water Storage Tanks Takes Knowledge
While the use of cathode protection along with protective tank coatings is not the standard protective method used today as many owners rely solely on tank coatings, its popularity is growing.
This is based on the continued findings of water storage tank engineers using and testing this method.
When the corrosive process is understood at the chemical level, it is easier to find new ways to prevent the chemical reactions that lead to corrosion.
Regardless of whether choosing cathode protection with a tank coating or the coating alone, it is critical that water storage tank services use the right one and apply it correctly.
Learn more about corrosion-resistant coatings in Part 2 of this article!