What Is Salt-Air Corrosion?

Salt-air corrosion is the accelerated deterioration of metal caused by airborne salt (chloride) deposits combined with moisture. On HVAC equipment it attacks the outdoor coil's aluminium fins and copper tubing, along with cabinet fasteners and electrical contacts, progressing faster than ordinary weathering.

Also called: salt corrosion · salt spray corrosion · coastal corrosion

Why it matters to you

Salt aerosol carries inland from the sound and the ocean, so exposure is a matter of degree rather than a line on a map — a unit near open water sees far more than one several miles inland behind tree cover. The damage concentrates on the outdoor coil, which is precisely the component the system depends on to reject heat.

What to do about it

Rinsing the outdoor coil with fresh water is the single most useful thing a homeowner can do, and the closer to salt water the more often it is worth doing. Use a gentle flow and never a pressure washer, which bends fins and makes the airflow problem worse.