Formicary Corrosion

Formicary corrosion is caused by a chemical reaction that can occur on the condensation that forms on evaporator coils. While it tends to have the biggest impact on copper and copper alloy coils, it can also impact aluminum and steel evaporator coils. The corrosion occurs when volatile organic compounds and other airborne acids collect and mix with the condensation water on the coils, causing a chemical reaction that corrodes the underlying metal. Interestingly, ants also cause formicary corrosion because they secrete organic acids that also cause the corrosion (formicary literally means “ant nest.”) While the HVAC industry has developed protective coatings for the coils, routine cleaning remains the best defense against formicary corrosion for both coated and uncoated coils.