Two Kinds of Corrosion, Two Different Problems
Galvanic corrosion is the visible one. Aluminium fins sit in direct contact with copper tubing, salt water bridges the two dissimilar metals, and the aluminium — being the less noble of the pair — gives up its material. You see it as white powdery deposits, fins that crumble when touched, and a coil that has visibly thinned along its windward face.
Formicary corrosion is the one that catches people out. It attacks the copper itself from the inside, driven by organic acids rather than salt, and it bores microscopic tunnels through the tube wall. There is nothing to see from outside. The system simply loses refrigerant slowly, gets recharged, loses it again, and eventually somebody works out the coil has been porous the whole time.
What an Assessment Involves
We take the condenser fan assembly off and look at the coil properly, which is not the same as shining a torch through the guard from outside. The windward face — usually the one pointing west or southwest here — tells the real story.
Fin density gets measured against what the unit left the factory with, tube surfaces are checked for pitting and staining, the cabinet base is inspected where water pools and salt concentrates, and electrical terminations are examined for the green bloom that precedes an intermittent fault.
- Distance and exposure to open water, and which way the prevailing breeze hits the unit
- Fin condition across the windward face compared with the sheltered side
- Pitting, staining and thinning on the tube surfaces themselves
- Standing water and salt concentration in the cabinet base pan
- Corrosion at contactor terminals, disconnect lugs and the fan motor housing
- Any factory coating still present, and how much of it is left
Cleaning, Treating and Coating
Salt that has settled on a coil has to be rinsed off, not blown off, and it has to be rinsed with something that will not attack aluminium. Aggressive acidic coil cleaners strip deposits impressively and take a measurable amount of fin metal with them, which is why we use pH-neutral products and low pressure from the inside out.
On a coil still in sound condition, a flexible epoxy or polyurethane coating applied after cleaning puts a barrier between the salt and the metal. It is not a repair — it will not bring back fin material that has already gone — but applied to a coil with life left in it, it meaningfully extends the years you get.
A word on honesty here, because this is an easy service to oversell. Past a certain point a coil is finished and coating it is throwing money at a component that needs replacing. Homeowners who have used AC Repair Estero more than once have generally heard that verdict at least once.
Keeping It From Coming Back
The single most effective habit is a monthly freshwater rinse of the condenser coil with an ordinary garden hose, done gently, in through the fins from the inside where you can reach. It costs nothing and washes the salt away before it has time to work.
Beyond that: keep landscaping back so air can move around the cabinet, resist the temptation to box the unit into a decorative enclosure that traps salt spray, and if you are replacing equipment within sight of the water, specify a coastal package with factory-coated coils from the outset.
Questions We Get Asked
- How much life does a coating actually add?
- On a coil caught early, a well-applied coating and a sensible rinsing routine typically add three to five years before corrosion becomes the limiting factor again. On a coil already thinned through, it adds very little, and we will tell you which one you have before you commit to anything.
- We are two miles inland. Does this still apply?
- To a lesser degree, yes. Salt aerosol carries several miles on a sea breeze, and properties along the Estero River corridor still show it. The effect drops off with distance, so an inland unit might want an annual rinse where a beachfront one wants a monthly one.
- Can I have this done at the same time as a service?
- Yes, and it is the sensible way to do it. The coil has to be accessed and cleaned either way, so combining the assessment with routine servicing saves a second visit and a second labour charge.