The screws in the neutral bar all all rusting. What type of lubricant should be used? The box is only 16 yrs old.

None, the rust needs to be removed, or the rusty part needs to be replaced, and the cause of the rust needs to be corrected.

Any corrosion on the exposed surface of wires needs to be cleaned off also.

If any circuit breakers got wet, they need to be replaced with new.