One single drop of liquid is enough to destroy large portions of a PCB.
Nowadays electronics is so tiny that it will have it totally wrecked, into a not repairable state.

When it comes to metal, it is by no means any better; aluminium will corrode badly, steel too, even stainless steel (just lasts a bit longer). The metals used on a PCB withstands even less, the PCB itself can be seen as a sponge .

As soon as you have a tiny bit of corrossion – tight and fine tolerances are gone, a focusing ring is one nice example. A lens as a whole is fine mechanics about as fine as it gets, the same is a camera body. Inside there is an “embedded system”, electronics adapted for the use.

Seals help stop ingress, but they wear as there is moving parts, and will eventually wear out.

Now note that *fine* mechanical fittings will act partly as sealing; as water has surface tension it won’t enter through such openings by itself. ( This is related en.wikipedia.org/wiki/Capillary_action )
Temperature, heat and cold-transitions, will add to the danger though. A hot item with a “breathing hole” that gets covered by moisture (e.g. a water droplet) will suck that droplet in throught the hole as it cools down.
All detergents contain chemicals that remove or lessen surface tension, why they are an extra challenge for any kind of sealing.

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