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Formicary Corrosion

May 2, 2013 | Blog

Last Updated: Aug. 21, 2019

What is Formicary Corrosion?

The last thing any Californian wants to deal with in the middle of summer is a broken air conditioning unit. Many Central Valley homeowners have had to deal with a broken AC, but few know what causes it. One of the most common causes of broken ac units is formicary corrosion.

Formicary corrosion is a type of corrosion specific to copper coils in outdoor ac units. The corrosion isn’t visible to the eye, but if you put it under a microscope, you can see hundreds of tiny holes in the coils. That’s why formicary corrosion is also known as pinhole corrosion or ant nest corrosion. This type of corrosion is unique because it happens from the inside out, making it difficult to catch.

What Causes Formicary Corrosion?

There are several causes for formicary corrosion, but the most common is a chemical reaction between oxygen, water and a volatile organic compound (VOC). VOCs are most often found in household cleaning supplies. Once VOCs are released in the air, they end up in the ductwork and cause corrosion in the coils.

Engineers are making units more efficient to keep up with environmental regulations. This means they are designing thinner coils, making them more susceptible to corrosion. Regulations are also requiring refrigerants that are less harmful to the environment. The most common refrigerant, R410-A, operates at a higher pressure, increasing corrosion.

How to Fix Formicary Corrosion?

The worst part about formicary corrosion is that it is not an easy fix. Instead of one hole, there could be hundreds. If your coils have formicary corrosion, you have three main options:

1) Apply a sealant to the coils.
2) Replace the coils.
3) Replace the air conditioning unit.

Applying a sealant is usually the most inexpensive option for formicary corrosion. While it is an effective solution, it could be temporary. If the damage is bad enough, your ac technician might recommend replacing the coils or the whole unit. Replacements can get expensive fast, so if you’re on the market for a new ac unit, look for a unit with aluminum coils. Formicary corrosion only affects copper coils, so units with aluminum coils will not corrode.

Formicary corrosion can be difficult to fix, but the experts at Lee’s Air can help get your AC running again. If you suspect formicary corrosion in your AC unit, give us a call!

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