We have also experienced this with our 2014 Victory caravan.
To date we have changed some satin chrome cupboard handles that have shown early signs of rust, both taps and have touched up painted cooker side strips.
We also have signs of rust on radiators in the shower room.
Caravans are prone to condensation whatever you do, they heat up during the day and cool down at night.
Ours is by the sea so the salt air doesn't help.
Our external tv aerial is changed every 3 years as the salt air corrodes the fittings inside the box.
I fear it is just one of those things owning a static caravan.
They will be made to a budget so I am not particularly surprised.
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