wasn't there a cyclocross bike where the maker had purposefully rusted the frame for looks. I will try to find it.
There is another, way more rusted one out there..hang on,
I have a '91 steel mountain bike that I bought new, used hard and put away dirty for quite a while. Even stored it outside for at least a year when I didn't have storage inside. It still looks great today, 21 years later. You can see it in the "90's mountain bike thread"...first post.
Also have a steel Bianchi San Jose that I've done nothing special with. Just ride and put away.
Take my anecdotal experience for what it's worth.
To deal with it, I do 15 minutes of annual maintenance. Use steel wool on the rust spot (careful not to sand the nearby paint.) Then put clear nail polish over the bare metal. You can use colored nail polish as a touch up paint. It's surprising too how long it lasts. The only problem is getting an exact color match. When that's not possible, clear polish seems like a good alternative.
Funny thing is......I own a multiple titanium and carbon bikes but my everyday commuter is a steel bike that I ride in the either rain or snow.
If a person would not consider a steel bike because they have this notion that a little water will hurt them I feel bad for them because they may be missing out.
My daily rides have been exposed to some really nasty weather and although we don;t get as much rain as some places we get our fair share and winter lasts for 6 months where the rides can be snowy, wet, icy, or a mix of all three and then there is all that road salt and sand.
This was my commuter and after 4 seasons of abusing it I figured it was too nice a bike for that and use it as my dedicated commuter... with steel bikes I put a little light oil on a rag and wipe them down when they are clean and also apply this to the exposed cables and bolts.
I touched up the rear stays as they had a bunch of scratches and that was some years ago.
The coating is so light you can run a finger over the frame and not get dirty but is more than enough to make the bike shed water like a duck.
I also use turtle wax on some bikes that see less frequent use and may see a little bit of rain from time to time... the bikes that get used constantly also get wiped down regularly.
I let mine drip-dry overnight. The drivetrain gets a wipe down after repeated rain rides and I re-lube when the drivetrain starts making noise. I've been out riding in the rain nearly 200 times in the last three years (I bike you commute full-time in the Pacific Northwest, you learn to ride in the rain) and my bike has no rust on it. Contrary to BF mythology, riding your bike in the rain will not eat your derailluer, ruin your chain and rust your frame. Or maybe I am just lucky.
I have a 35 year old Schwinn Traveler that has been rained on, ridden in Minnesota winters, carried in river crossings, and just generally abused. Has minor rust and is still getting a fair amount of use.
So I fail to see much of an issue for rust on the frame.
We have met the enemy and they is us.
If I have just ridden home in the rain, the last thing I am worried about is drying off my bike! I'm headed straight for the shower. Plus, if my 25 year old steel road bike rusts out, that's an excellent reason to get a new bike! Alas, it would seem that I am years away from that eventuality...
Salt corrodes exposed steel. Framesaver on the inside and wipe down the unpainted exposed parts and your frame will be fine.
One more vote for "don't worry about it." My 1984 Schwinn was used plenty in the rain, and it only has light surface rust where the paint is chipped. Most of those chips are decades old. The only thing I really did was make sure it was always put away in a dry place, plus cleaning and lubing the chain when it started to get noisy.
If I ride one wet, I wipe it down after takes less then a minute. I keep my chains lubed, and cables are consumables anyhow.. the tempo frameset I just got though, got put away wet a lot, it's taking sanding it to bare and cleaning up then paint up to correct.
I notice though after working on many old bikes from the 70s, very few of them have any sign of rust internally. Seems like if you keep them indoors... at least in the Midwest climate... they last pretty much indefinitely.
I would consider it for a bike that saw a lot of winter action though.
my beater bike is a scratched/steel '97 gary fisher tassajara. i'm pretty sure it had a hard commuter life before i bought it.. it gets ridden ONLY in wet conditions. i bounce it a few times before i bring it in, mostly to keep the dirt off my carpet and then it drip dries. i occasionally wave a rag at it. after several years of this abuse, it is still as rust free as the day i bought it.
I have a low-middle range road bike (nakamura) to commute everyday and I don't care about it. I also have a 1984 bianchi fully restored and an old peugot also fully restored that I ride on sunny sunday afternoons and take really good care of.