What Is Galvanic Corrosion?

Galvanic corrosion occurs when two dissimilar metals are in electrical contact with an electrolyte present — in coastal HVAC, typically copper tubing against aluminium fins with salt-laden moisture bridging them. The less noble metal corrodes preferentially, which is why aluminium fins fail around copper.

Also called: dissimilar metal corrosion · bimetallic corrosion

Why it matters to you

This explains why some coastal coils fail from the inside out while looking acceptable from the outside, and why all-aluminium coil construction is offered as a coastal option: removing the dissimilar-metal junction removes the mechanism.

What to do about it

You cannot inspect for this meaningfully from outside the cabinet. What you can do is reduce the electrolyte — rinse salt deposits off — and, at replacement time, ask whether all-aluminium construction is available for your equipment.