PCB corrosion? Having been in the industry, I'm not sure what you mean by this. Moisture/water won't affect PCBs, however it can affect the circuits (via shorting) if for example a circuit is active when it becomes exposed to water.
PCBs can be affected by poor manufacturing, technically speaking, referring to poor cleaning after assembly.
In the old days, the PCBs would go through a chemical wash.
Modern assembly processes no longer involve chemicals, they use aqueous washes now.
A PCB that isn't cleaned properly after assembly can cause problems later down the road, but the chances of of a major camera manufacturer skimping in this area is essentially zero.
The bottom line, this effort isn't necessary. Just don't drop them into the drink.