Formicary Corrosion

A relatively recent phenomenon in HVAC construction has been the emergence of formicary corrosion on copper tubing in HVAC systems. The corrosion presents as spider-like lines on the surface of the tubing, eventually leading to tubing failures and resultant refrigerant leaks. The refrigerant leaks cause a loss of system capacity and manifest in relatively new construction. These leaks have been observed in the equipment of many manufacturers.

The corrosion is caused by the presence of volatile organic compounds (VOCs) in the air surrounding the copper. VOCs in the air are caused by the off gassing from many building materials and cleaning products such as carpet, paint, household cleaning agents, etc.  Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and the majority of them have been proved to be detrimental to human health.

Some of my recent engagements have involved the determination of how the interplay of VOCs with copper tubing have taken place.  On the basis of the investigation of this phenomenon in several buildings, I have concluded that the cause of the corrosion is high levels in VOCs due to the inadequacy of ventilation. Inadequate ventilation can be the result of either poor ventilation design or a misunderstanding of the ASHRAE ventilation standard, ASHRAE Standard 62.

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