Blowers and moisture

Try www.icmcontrols.com . They have motor speed controls to overcome the moisture problems.

It is difficult to be confident with any suggestion since I have no idea of the environment that this blower operates in.

However, I think from what you have said your base problem lies with the humidity of the air (assuming it is air you are compressing)which may be inherent to your location or the result of other processes in the vicinity of your blower intake. If the blower has long down times and the inner temperature drops below the dew point of the air then you may want to look at some heating for the blower cavity to keep the internal temperature above the dew point. Maybe heat the oil with an oil circulation circuit as you would for a machine on standby that could be called into service with short notice. You also mentioned a dryer for the incoming air but without knowing the size of your blower I suspect that the cost might be fairly high as these blowers tend to shift a reasonable amount of air.

Alternatively, if there are other blower units running you could maybe siphon off some warm air for circulation through the redundant blower.

I would definitely check with the manufacturer before coating the lobes and if you inject lubrication into the blower your process will need to be able to tolerate the oil in the air.

A cost benefit analysis will ultimately determine what you should apply as a solution.

How about plating the ferrous parts?

OR! Put a small port on the intake side and inject something like WD-40, (Water Displacement formula number 40,) as the pump is winding down after being powered off? This can even be made automatic with a relay, timer and small solenoid valve. You can buy WD-40 in quart to 25 gallon quantities.

Both methods have worked for me in a marine environment.

The appropriate action to prevent rust formation is dependent on the type of contaminants in the gas (air?) you are compressing and the moisture content in the gas. Although it is fairly certain that rusting and seizure of the blower lobes would occur if the temperature in the blower decreased below the dewpoint of the moisture in the gases, it is not necessary to achieve a condensation type situation to form rust on a steel surface. Rusting of steel will occur very rapidly; I have personally seen visible rusting occur in < 15 seconds if the contaminants on the steel surface will deliquesce moisture from the air. [You wont even see or detect any moisture on the steel surface.] Calcium and magnesium based compounds (especially chloride complexes) will deliquesce moisture from the air and form a localized concentrated solution of corrosive ions on the surface.
Personally, in a situation where there is any question whether there are acidic vapors (esp. those containing chrolide or sulfate ions around) I woud recommend a coating for the steel surface.