Duct rusting

[Kaiden24]

Quick background: We just bought our home and before summer rolls around I wanted to see if my evap coil needed cleaning, its a cased coil so I pull the cover off and I find rust just above the coil along the edge of the casing and I find what looks like water spots on the duct above the coil. I rubbed the spots and it was chalky white in color... Should I be worried? This system according to to previous owner is 4 years old. Why would it rust? Thanks in advance.

Kaiden

[Shophound]

Discharge air coming off a cooling coil is very moist, almost saturated. If insulation is marginal in casing or duct (plenum) then you may have condensation occurring inside case. You may also have moisture blowing off coil and collecting on casing sides.

Did you find the coil to be dirty?

[t527ed]

is there a humidifier on system??

[Kaiden24]

The coil has some rust on it and the same chalky substance in between the fins but other than that it is spot less. The substance doesnt seem to be blocking any air flow. There is a trion filter on the system.

Yes on the humidifier but it is connected to the return line.