It will not happen to you, but maybe you can point someone out:
It is autumn and fallen leaves desperately try to hibernate in that part of the engine room of your classic where the windshield wipers live. The body just in front of the windscreen and behind the engine, where there is often a fan for the interior.
That leaf is moist or attracts moisture when it is dry. And if you don't pay attention, it will study for compost all winter.
And if there is no rust ...
The stuff is biodegradable and is usually easy to spoon out by hand.
Re-blowing with the compressor ...
Klaar
Not just rust. With me, the fuses are in such a container and you can already guess what will happen if everything fills up.
Incidentally, the central computer is also located in that location in much more modern Audi's. It also does not improve from such a bath.