Controlling Aluminum Corrosion in Cooling Tower Systems

example of galvanic corrosion on aluminum and steel surface

How Do You Control Aluminum Corrosion in Cooling Towers?

Aluminum is light weight, easy to tool and has been used in many industries for years.  Unfortunately, aluminum has different solubility and corrosion resistance characteristics than most materials common to cooling towers and recirculating water systems.

Most water treatment strategies are designed to address corrosion and scaling concerns on a variety of materials, but water chemistry that protects metals like steel and copper can present an aggressive situation on aluminum.  Aluminum is a very stable metal in dry air, but aluminum components treated by recirculating water systems is another matter.

What’s the Best Water Treatment For Aluminum Systems?

The corrosion rate of aluminum increases when the pH of the water exceeds 8.0 and becomes severe when the pH exceeds 8.4.  A treatment program designed to protect aluminum components should maintain the pH of the water between 7.5 and 8.0.  Unfortunately, this has an adverse effect on ferrous metals in the system.  The corrosion rate of iron is elevated significantly in this neutral pH range.  One must carefully weigh the benefits of a neutral pH program for systems constructed primarily of ferrous metals against the cost of replacing aluminum components with plastic or brass pieces.

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When the cost favors a neutral pH program designed to protect expensive aluminum components such a molds, acid must be used to maintain the pH of the water within the 7.5 – 8.0 range.  Chardon’s pH adjustment chemistry may be fed using the inhibitor relay, although a controller capable of controlling based on pH offers the most reliable solution.  For systems with accurate pH control, Chardon will then determine the best corrosion protection options, depending on other variables within the system.  Systems with softened make-up present an additional problem.  The combination of low calcium hardness and low pH can significantly accelerate corrosion on ferrous metals.  To prevent this combination from corroding the system, soft water can be blended with hard water to deliver approximately 100 ppm of calcium hardness in the system water.

Why can’t I use automotive antifreeze designed for aluminum engine blocks?

Many of these anti-freeze products contain silicate-based corrosion inhibitors and are designed for closed systems that don’t evaporate.  When introduced to an evaporative cooling system, these silicate-based corrosion inhibitors will form passivation films on aluminum.  While the aluminum might not corrode, these products also form silica scale on heat exchangers.  The effect of silica scale on heat transfer is nine times as great as calcium scale.  Silica scale is extremely difficult to remove, without further damaging the aluminum.  This type of chemical treatment for aluminum is not recommended.

Choose Chardon Labs for Effective Industrial Cooling Tower Treatment

At Chardon Labs, we strive to provide valuable resources for companies and industries that depend on adequate, and proactive, cooling tower treatment. We also understand that, sometimes, it’s easier and safer to call in the professionals.

If you would like us to take a look at your cooling tower, or you wish to receive a quote for our commercial cooling tower services, you can call us anytime at 1-800-848-9526 or fill out our online contact form. We’re always happy to answer your questions, provide insights and additional resources, and discuss the benefits of partnering up for your water treatment needs.

We encourage you to learn more about our commercial cooling tower treatment services online, and we look forward to helping you control aluminum corrosion in your cooling towers.