Understanding Coil Failure Modes
Modern evaporator coils face multiple corrosion threats that can lead to premature failure. Understanding these failure modes helps explain why CoilShield protection is essential.
Galvanic Corrosion: The Primary Threat
When copper and aluminum are in contact in the presence of an electrolyte (like condensate water), they form a galvanic cell—essentially, a battery. Current flows. Electrons move. And the aluminum—being more "active" electrochemically—corrodes preferentially to protect the more "noble" copper.
Your coil is literally eating itself at every copper-to-aluminum joint, every hour it operates.
From the Carrier/Bryant Installation Manual: "Take precautions to ensure Aluminum tubes do not come in direct contact or allow for condensate run off with a dissimilar metal. Dissimilar metals can cause galvanic corrosion and possible premature failure."
Formicary Corrosion: The Hidden Destroyer
Formicary corrosion creates microscopic tunnels through aluminum fins. Often caused by acidic compounds from household products (cleaning agents, adhesives, building materials), formicary corrosion can progress undetected until failure occurs. The name comes from the ant-farm-like tunnels it creates through the material.
How Thin Is the Line Between Working and Leaking?
The Carrier 37MHRAQ mini-split specification lists evaporator tube wall thickness: 0.24mm (0.00945 inches)—less than 1/100th of an inch. That's all that separates your refrigerant from your living room. Corrosion doesn't need to eat through much material to cause a catastrophic failure.
Environmental Accelerators
While all coils face electrochemical corrosion, certain environments dramatically accelerate the process:
- Coastal areas: Salt air increases conductivity of condensate
- Pool facilities: Chlorine vapor is extremely corrosive
- Agricultural operations: Ammonia and fertilizers accelerate corrosion
- Industrial environments: Chemical exposure destroys coils rapidly
These environments often have warranty exclusions, leaving you without manufacturer protection when failures occur.