Nowt wrong with a bot o rust !
My daughter's boyfriend has been running his new YBR125 through winter and when we were at the Scottish bike show this weekend he complained that the chain was rusting on the side plates. I explained that the critical component is the o-ring area, and as long as that is lubed and not rusty the outer sideplate rust isn't really a sign of a knackered chain (although it is contagious once it sets in)
I spin the back wheel while holding a brass wire brush to the outer side (if the chain is really bad), and then chainwax or grease on the outside keeps the plates free from corrosion for a long time and I use any oil, thicker the better, for the o-rings.
I used to always run a bike daily through winter on very salty Scottish roads, and if the chain ever developed a tight spot a soak in white spirit (brush cleaner) for a few hours, then hung up to dry for a few hours, then an overnight bath in the old engine oil tray worked wonders.
If a chain tightens during winter I keep it going till spring arrives and the salt has gone, then change the C&S...cannot see the point in murdering a new C&S mid winter