Aluminum air pipes

Biology protects corrodable irrigation pipes

Oxidation in aluminum irrigation pipes is a secret enemy. If you don’t see corrosion, it might not be that bad. Until it leaks or loses its structural integrity, then breaks.

But maybe the invisible enemy can be just as bad, according to Scott Bryan, director of technical sales for Cortec Corp. in Minnesota.

Cortec specializes in biological water treatments and additives for industry, municipalities and agriculture. They have ongoing water treatment projects and products all over the world. They recently turned their attention to the corrosion that eats away at the interior surface of aluminum irrigation pipes.

Oxidation is clearly the culprit, Bryan explains. Oxidation does not occur when water is circulated through the system. When the system remains inactive for a while, the water is drained. At least most of the water is drained.

Bryan says that the water remaining in the bottom of the pipe protects the aluminum from corrosion because it eliminates contact with the atmosphere. Corrosion only occurs on aluminum in contact with air, but keeping the pipes full at all times is out of the question.

But coating the exposed surface with a corrosion inhibitor could solve the problem. The company was founded on the principle of providing environmentally friendly biological solutions to protect against corrosion.

Irrigation systems provide essential water for food production, so any solutions must be benign, Bryan said in a phone interview.

How much land is affected? The United States has over 50 million acres of irrigated land, while Canada has nearly two million acres. Any aluminum exposed to air is sensitive. The risk is greatest in areas where groundwater contains a high level of chlorides and sulphates.

On October 14, Cortec announced that it had developed EcoLine AL-Cor for the protection of aluminum irrigation pipes.

Bryan says it’s a water-based corrosion inhibitor additive based on amino acid derivatives and has been certified by the US Department of Agriculture for 81 percent bio-based content.

“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 tests at 104 F (40 C) over a five week period showed 91.18 percent protection for the AL 3003 metal and 99.03 percent for the AL 1100 metal.

The product is applied by the injection system of the irrigators. While all products have the same concentration, the flow rate is controlled by the amount injected into the tank. A dose of 250 parts per million was applied in the tests AL 3003 and AL 1100.

Protected hoses mean more efficient watering. Corrosion causes clogging, which narrows the pipe, reducing water flow. Corrosion also makes leaks and downtime more likely.

Anyone who has served in a volunteer fire department has learned that water flows more efficiently through a smooth hose compared to a rough identifying surface (inside diameter).

“We see this aluminum corrosion problem in other areas, not just in irrigation. Anywhere you have exposed aluminum there is a risk of oxidation. Aluminum is an amphoteric metal, it reacts both as a base and as an acid. You get metal loss with low pH and high pH. This makes it more difficult to protect against oxidation.

“So any corrosion inhibitor for aluminum has to be somewhere in the middle neutral zone. Seven is good, but a corrosion inhibitor can be somewhere between six and eight low. Sometimes when you are dealing with well water, you can have a major pH problem that is corroding your pipes.

“Aluminum is normally resistant to corrosion, except in the presence of high or low pH when it forms an oxide which dissolves. Our chemistry leaves a thin residual film on this aluminum surface, a single molecule thick.

Bryan says Cortec doesn’t deal at the retail level. They build relationships with equipment and service retailers and continue to work with these companies to meet the needs of their customers.

Cortec works with three major irrigation supply companies in the United States that are making the new EcoLine AL-Cor technology available to their farmer customers.

Bryan says Cortec is looking for water treatment or irrigation companies in Canada who are interested in testing.