Vintage Synth Repair

Someone wants me to fix a Roland RD-300S keyboard(7 notes not
working). I opened it and removed 58-keys to find that there is rust
on 2 spots on the PCB. I plan to put some jumper wires between the
diode pins and traces to fix the keyboard but is there anything I
could do to prevent it to rust more? The keyboard supposedly started
to do this a few months ago while the last time it went outside was
years ago.