Originally Posted by
Longfemur
Don't worry about it. It's totally insignificant. You don't want your frame to rust, but your chain and cogs are easily replaceable items (plus, they aren't the kind of things that will rust through). They are exposed, bare steel, and if you use any kind of lube that washes off easily in rain (especially wax or dry lubes), you will see rust like this. Use a more persistent lube. Just plain lubricating or motor oil works well for this kind of application. Apply sparingly, and you will be fine.
speaking of things unlikely to rust through, you really shouldn't worry about frame rust either. unless you forget to bring your bike inside for fifteen years, chances are you're not going to do any harm that isn't reversible. Go check out the C&V forum if you don't believe me—"oxalic acid" is the search term.