As we all have a can of ACF50 lying around in the garage, I wonder whether this could be sprayed onto the polished alloy bits, then gently wiped over? I'm just not sure how this would react when it is heated up, but if a small sample area is treated first, it can't do much damage.
I am amazed how good that stuff is at protecting normal metal parts. I carefully sprayed all crucial parts when my Threee Wheeler was new, including the front hubs and inside the brake discs, which always go rusty in next to no time, and it certainly kept those bit clear of surface rust.
[Beginning to get the best out of the ARP4]