Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


Formicary Corrosion

Last updated: November 19, 2016

What Does Formicary Corrosion Mean?

Formicary corrosion is a type of corrosion caused by organic acids such as formic acids and acetic acids. Formicary corrosion affects coils in a cooling system in nearly all branches of the industry. This corrosion attacks copper and copper alloy tube walls, and is associated with pinholes in the copper tube walls in cooling systems.

Formicary corrosion cannot be seen with the naked eye, which makes it difficult to detect the problem before the damage is already too severe and causes a coil leak.


Corrosionpedia Explains Formicary Corrosion

Formicary corrosion mainly occurs in copper-based alloys and HVAC coils, which are also often made of copper. In copper, this type of corrosion has the appearance of an ant nest, hence it is often referred to as “ant’s nest corrosion.” It is also regarded as pinhole corrosion because of the small size of the actual holes in the copper.

Formicary corrosion occurs out of a chemical reaction between oxygen, water and an organic acid in the coil. This corrosion displays a network of microscopic corroded tunnels within the tubing wall. This is analogous to ant nest-type structures, which are bigger than the surface pinholes above them. To stop further formicary corrosion, one needs to remove any of the abovementioned three ingredients. The coil can also be affected by pitting corrosion. Pitting and formicary corrosion can occur within a few weeks after installation. Formicary corrosion causes premature equipment failure and reduces the longevity of coils and systems.

The organic acids that cause formicary corrosion are abundant in home products and the industry, such as acetic acids; or the derivative of acetate is abundant in adhesives, paneling, particle boards, cleaning solvents, vinegar and foam insulation. Similarly, formic acid is also abundant in cosmetics, disinfectants, latex paints, plywood and dozens of other materials.

Formicary corrosion is more likely to occur in places where there are high levels of humidity. A high level of humidity causes the presence of more water to react with the other components in the air and enhances the corrosion rate.



Ant's Nest Corrosion

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