Rust on chains, cogs and brazeons is not a problem. Just lube the chain with wet stuff and the rust will dissapear. You can spray the cogs with WD40 but be really careful, WD40 can get inside the bearings and dissolve grease. As for brazons, just wipe with an oily rag.
I use car wax on the frame to prevent rust.
Check inside the frame for water collecting in the BB shell.