Corrosion Control in Water Storage Tanks

May 2, 2013

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You see them in every city – water storage tanks. They come in all shapes and sizes, and exist above ground and on ground level. No matter their configuration they all experience degradation from the same cause – corrosion.

Corrosion comes from the interaction of three elements: metal, an electrolyte and oxygen. The metal releases electrons which causes the metal to revert to iron oxide (we call it rust). The electrolyte is the medium through which the electrons pass. Water is more conductive than air which is why rust occurs more rapidly in high humidity conditions. The inside of a tank faces different conditions than the outside of a tank, because of different electrolytes and conditions.

Two primary means exist to control corrosion in water tanks: cathodic protection and protective coatings. Cathodic protection can be passive, in which a different metal is placed within the tank and is ‘sacrificed’ in place of the tank itself – corrodes instead of the tank. Active cathodic protection involves the use of dc current to prevent corrosion.

Surface coatings or linings are utilized both inside and outside the water tanks. A combination of the two systems (cathodic and protective coating) provides the most effective protection. Coatings will provide the bulk of the protection both inside and out.

There are many different kinds of protective coatings available. The type utilized is dependent on the individual application – internal, external, the condition of the water being stored, the climate conditions, and more. That is why it is so vital to utilize industrial painting contractors who are experienced in tank protection.

Consider just a few of the coating options. Direct to Metal Acrylics (DTM) are water based coatings that provide strong performance with economy. They are used primarily for exterior surfaces. Polymers, which are based on acrylic formations, with additional enhancements are also widely utilized.

High solid polyurethanes are low VOC products that provide excellent strength and abrasion resistance. They come in various formulations which allow them to be utilized in a wide variety of applications.

High solids epoxies are utilized most often in the interior of water tanks. They provide excellent coating and corrosion resistance. They meet the requirements for safety, both volatile organic compounds safety and long term water quality testing.

The coating of water tanks is critical to their lifespan and enabling them to withstand the destructive effects of corrosion. New construction coating requires a different process than recoating existing tanks. That’s why it is important to employ a painting contractor who has water tank painting experience and a proven track record. There is too much at stake to cut corners or take chances.

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