The main point one can criticise about the build of the Rancilio Silvia is that it is not all stainless steel. While many important parts like the drip tray and the cup holder are, the main frame (black) is just powder coated steel. This means it can rust and according to reports on the internet it actually does.
However one can do some small and cheap modifications to drastically reduce the risk.
Rust is the product of the reaction of steel and oxygen in the presence of water, so to prevent rust one either has to remove oxygen or water.
The powder coating of the frame typically removes both, but over time scratches penetrate the coating and the frame can rust.
The first step to prevent rust is therefore to prevent scratches on the steel frame. To this end one can add small rubber knobs (8mm diameter) at places where movable parts come in contact with the frame
Prevent Water Splashes
The other thing one can do is to ensure that less water come in contact with the frame. Unfortunately the drain on the Silvia is quite short, so water splashes in all directions and can run behind the drip tray – especially if it is not moved all the way back. See the following video:
An easy fix to improve the situation is to extend the drain with a silicon pipe (19mm inner diameter) for about 4cm. After the modification, the water hardly splashes any more. (again this is the worst-case scenario with the drip tray all the way in the front)