The legs of many ceramic capacitors are rusted, on both side of the board. Only one appears to be weak when I gently move it back and forth.

Should I desolder them all and replace them? I am thinking of only replacing the weak one. For the rest, clean it up with tooth brush and some kind of chemical, then put some grease on it.

What would you advise to do? What chemical would work best for this? How about the grease?

Currently, it appears to work good. The board is for power, pedal, audio and USB out of a digital keyboard. I open this it because some keys don't work. I think it's highly likely just rubber contact issue.

Then I found this issue. Possibly they spilled something, or left it in a very cold garage.

 

The legs of many ceramic capacitors are rusted, on both side of the board. Only one appears to be weak when I gently move it back and forth.

Should I desolder them all and replace them? I am thinking of only replacing the weak one. For the rest, clean it up with tooth brush and some kind of chemical, then put some grease on it.

What would you advise to do? What chemical would work best for this? How about the grease?

Currently, it appears to work good. The board is for power, pedal, audio and USB out of a digital keyboard. I open this it because some keys don't work. I think it's highly likely just rubber contact issue.

Then I found this issue. Possibly they spilled something, or left it in a very cold garage.

I would physically clean it with a dry brush and vacuum or air blast the dust away. I wouldn't worry about the weak one until you hear a performance issue.

The rust could be from a spill or from storing near a running motor or in the same closet as a bottle of bleach or many other things. In any case, trying to fix these old devices may result in a lifted copper trace as you try to desolder the component from the board (unless you have reasonable experience doing this). Also, if you decide to give it a try, I would add a blob of fresh of tin/lead solder to each joint before you start sucking up the old solder with solder braid, solder sucker or any other trick. Good luck.

 

I ended up cleaning it with alcohol, then with some baking soda, then alcohol, then air brush. I just left it as that like you said. Hopefully I don't have to deal with it later.