Vic, I design highly stressed rotating machinery for a living. I’m familiar with the properties of aluminum and steel.
That aside steel con rods do rust, mainly by my observation due to water from combustion and low oil temp. It doesn’t affect the non-ferrous con rod bearings.
The Lyco conrods do however have some sort of brown coating. No idea what it is, but it isn’t bare steel. They are much less likely to get rust. Same with the conrod bolts.
For example the bare (ground) steel surfaces on my milling machine or lathe corrode at the slightest contact with water or fingerprints, and have to be kept oiled with a special machine tool oil. This is IMHO equivalent to the surface of a cam lobe.
EDIT: Here is one of my actual conrods. My memory served me badly – it has no brown coating. But it wasn’t corroded at all
Steel parts are sometimes plated prior to final machining of areas that need to be locally surface hardened. IIRC copper/alloys are used. I’m not familiar with Lycoming rods, this could be a factor. Common on cams and followers.
