Just a generalization here.
If a circuit board is corroded, you can clean off the corrosion and reuse the circuit board as long as the terminals are in good condition after the cleaning. I have done it numerous times on circuit boards that get damaged from corrosion. When you are done with your cleaning process, just rinse well with warm tap water, followed by a final rinse with distilled water, shake off the worst of it, and let the circuit board sit to dry for a day. When you reassemble, squeeze some silicone grease into the connectors and connect them so the grease oozes out. Then you are great shape and it cost you nothing but your time. They sell special corrosion cleaning products to clean circuit boards, but I use household CLR.
My job for 38 years was designing circuit boards and specifying production processes for them, including the cleaning process. Many years ago before the EPA cracked down ozone depletion, circuit boards were cleaned with freon to clean off the flux. The environmental solution was to use a water soluble flux and the boards get cleaned with a purified water and then dried.
So, as long as the circuit board is well rinsed of your cleaning agent like CLR, and properly dried, it's generally a very safe process. Remember, I am talking about circuit boards, not complete assemblies like an assembled cell phone or camera for example. The circuit board must be removed, then cleaned & dried, then reassembled back into it's purpose. In the rare case example of an RV water heater with the circuit board in plain view, you should be able to clean the terminals without removing the circuit board. But then first disconnect your batteries so assure there is no power in the area.
I once bought a headed to a junk yard dead 1991 Mercury Capri which had open-to-the-environment non-sealed electrical connectors under the hood that were corroded. After my cleaning process and silicone grease protection to every connector, that cute little turbo convertible was back in full reliable service.