Oxidation within aluminum irrigation pipes is a secret enemy. If you don’t see corrosion, then maybe it’s not that bad. Until it leaks or loses structural integrity and then snaps.
But maybe the invisible enemy can be that bad, according to Scott Bryan, technical sales manager for Cortec Corp. in Minnesota.
Cortec specializes in biological water treatments and additives for industry, municipalities and agriculture. They have water treatment projects and products on the go worldwide. They recently turned their attention to the corrosion that eats away at the inside surface of aluminum irrigation pipes.
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Oxidation is clearly the culprit, explains Bryan. Oxidation does not occur while water is flowing through the system. When the system goes idle for any length of time, water is drained. At least most of the water is drained.
Bryan says water remaining in the lower part of the pipe protects the aluminum from corrosion because it eliminates atmospheric contact. Corrosion only occurs on the aluminum in contact with air, yet keeping the pipes full all the time is out of the question.
But coating the exposed surface with a corrosion inhibitor might solve the problem. The company was founded on the premise of providing environmentally friendly bio-solutions to protect against corrosion.
Irrigation systems provide water essential to food production so any solution must be benign, Bryan said in a phone interview.
How much land is affected? The United States has more than more than 50 million acres of irrigated land, while Canada has nearly two million acres. Any aluminum exposed to air is susceptible. The risk is greater in areas where groundwater carries a high level of chlorides and sulfates.
On Oct. 14, Cortec announced it had developed EcoLine AL-Cor for the protection of aluminum irrigation pipes.
Bryan says it is a water-based corrosion inhibiting additive based on amino acid derivatives and has been certified by the U.S. Department of Agriculture for 81 percent biobased content.
“The biodegradable active components are ingredients found in personal care products and food preservatives.
“These inhibitors form a protective film one molecule thick on the interior surfaces of irrigation pipes. Immersion testing at 104 F (40 C) over a five-week period, showed 91.18 percent protection for AL 3003 metal and 99.03 percent protection for AL 1100 metal.”
The product is applied through the irrigators injection system. While all product is the same strength, the rate is controlled by the amount injected into the tank. A dose of 250 parts per million was applied in testing AL 3003 and AL 1100.
Protected pipes means more efficient watering. Corrosion causes clogging, which narrows the pipe, thus reducing water flow. Corrosion also makes leaks and downtime more likely.
Anyone who has served on a volunteer fire department has been taught that water flows more efficiently through a smooth pipe compared to a rough ID (inside diameter) surface.
“We see this aluminum corrosion problem in other areas, not just irrigation. Wherever you have exposed aluminum, there’s a risk of oxidation. Aluminum is an amphoteric metal, it reacts as both a base and an acid. You get metal loss in low pH and high pH. That makes it harder to guard against oxidation.
“So any corrosion inhibitor for aluminum has to be somewhere in the neutral middle zone. Seven is good, but a corrosion inhibitor can be somewhere between high six and low eight. Sometimes when you’re dealing with well water, you may have a major pH issue corroding your pipes.
“Normally aluminum is corrosion resistant, except in the presence of high or low pH when it forms an oxide that dissolves. Our chemistry leaves a thin residual film on that aluminum surface, just one molecule thick.”
Bryan says Cortec does not deal at the retail level. They form relationships with equipment and service retailers, and continue working with these companies to meet the needs of their clients.
Cortec is working with three major irrigation supply companies in the U.S. who are making the new EcoLine AL-Cor technology available to their farmer clients.
Bryan says Cortec is looking in Canada for water treatment or irrigation companies that want to run trials.
