The Galvanic Cell in Your Air Handler
Modern evaporator coils are engineering marvels of efficiency. They're also electrochemical time bombs. Here's why:
To maximize heat transfer while minimizing cost, manufacturers build coils from:
- Aluminum tubes (excellent heat transfer, lightweight, inexpensive)
- Aluminum fins (maximize surface area)
- Copper connections (required for refrigerant line brazing)
The problem? When copper and aluminum are in contact in the presence of an electrolyte (like condensate water), they form a galvanic cell—essentially, a battery.
How Galvanic Corrosion Works
In a galvanic cell, two different metals are connected in the presence of an electrolyte (a solution that conducts electricity). The more "active" metal (aluminum) becomes the anode and corrodes, while the more "noble" metal (copper) becomes the cathode and is protected.
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.
The Condensate Electrolyte
Your evaporator coil works by being cold—cold enough that water vapor in your home's air condenses onto its surface. This condensate isn't pure distilled water. It contains:
- Dissolved carbon dioxide from the air (making it slightly acidic)
- Dissolved oxygen (enabling oxidation reactions)
- Dust, pollen, and particulates from the air
- Volatile organic compounds from household products
This condensate coats your coil surfaces constantly during operation. And it doesn't just sit there—it creates an active electrochemical environment.
How Thin Is the Line?
The Carrier 37MHRAQ mini-split specification sheet lists the evaporator tube wall thickness: 0.24mm
That's 0.00945 inches. Less than 1/100th of an inch.
That's all that separates your refrigerant from your living room. That's all that stands between "comfortable" and "catastrophic." And galvanic corrosion is working on that barrier every day, every condensation cycle, every summer.
The Solution: Cathodic Protection
CoilShield uses cathodic protection to reverse this process. By making your coil the cathode in an electrochemical cell, corrosion becomes thermodynamically impossible.
Our sacrificial anode system uses magnesium, which has an electrochemical potential of -1.6 volts, making it strongly "anodic" compared to both aluminum and copper.
When you connect magnesium to your coil system, the magnesium corrodes instead. Your coil becomes the cathode—the protected electrode. The galvanic corrosion that was attacking your coil now attacks the sacrificial anode instead.
No power required. No maintenance except eventual anode replacement. The same technology that's protected ships for 200 years.
Prevention Beats Replacement
Don't wait for galvanic corrosion to destroy your coil. Protect it now with CoilShield's proven cathodic protection technology.
Learn more about how CoilShield prevents galvanic corrosion today.
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