Hi @simong93 ,
Usually under the shields is where the problems are because the water gets trapped there and takes longer to evaporate which doesn't help if the power is reconnected before it has or stop the corrosion once it has evaporated.
The only chance, slim that it is, is to remove the shields and clean it and hope that it might work
You could try and use an ultrasonic bath to try and clean it but again I think that the damage is already done and it is too late.