Inverter's outdoor pcb

[kerrcell]

Recently in Malta we have experienced a major low voltage and also frequent power cuts for a whole week.During this whole month have not stopped discovering faulty electyronic pcbs of the outdoor unit of inverter type domestic air conditioners.
All vrvs tested indicated a seized compressor(locked).But what is usually faulty is the inverter card.It costs a lot of money and most clients decided to replace the whole a/c unit instead of repairing.What I actually noted is the is a certain amount of corrosion on the track side of the same pcb.Is there any spray sealed that could be applied to prevent such corrosion?

[The Viking]

Well, they are normally varnished on the back.
So I assume that any normal non corrosive, non conductive varnish could be used...

[Electrocoolman]

Its called "Conformal Coating" . RS components sell aerosols of it. A good electronics distributor should stock it.