[TenTec] Slightly off subject

[John King]

I am the owner of a number of Ten Tec Stations but have other solid state supporting devices. I have a great 600 mhz frequency counter which is solid state constructed on a good quality printed circuit board. The circuit board has a slight blueish green , what I suspect is slight corrosion, lightly coating the board.
I want to remove the slight corrosion and clean the board up to stop the corrosion but I don't want to damage the printed circuit in any way. Can someone suggest a safe solution and safe way to remove the slight corrosion and make it shine again. I don't to use a corrosive solution to clean the printed circuit board.
Based on YOUR EXPERIENCE, what are your safe recommendations that will clean the board and extend the life of the printed circuit board????
Thanks, and 73, John, K5PGW