HI I have a few old steel framed bikes, couple of hybrids and the rest road bikes, none very valuable. Some of them have minor rust spots, little areas and i am actively using the bikes for excercise, riding around town etc. in Los Angeles including coast path rides (where there's sand and salt water etc.) So I dont want to leave surface metal exposed to rust more. So i experimented with probably the least valuable bike which is a 1995ish Trek Multitrak 720 that had some rust spots. I went to home depot and got some sand paper that is designed for metal. I got one pack of the stuff that comes with 3 grades of sandpaper, course medium and fine. I got a can of Rustoleum auto primer spray paint. Taking advice from a salesperson, I did not get Naval Jell product (that removes rust but is very toxic and caustic ) with the thought, lets see if i can get the rust off 100% with the sandpaper before turning to that product. I also got a can of this other Rustoleum paint product which is designed to paint over rust when you cant get the rust off completely.

So i sanded off some little spots of rust with the course sand paper (didnt use fine or medium) and then i spray painted the primer paint to cover the areas of exposed surface metal.

I didnt need the other Rustoleum product because i didnt leave any rust after sandpapering.

So now on this bike i have removed the rust and covered up the exposed metal.

So now the bike is rideable without my worrying about it rusting.

It looks bad because it has some areas of gray color primer, but I dont really care.
Its just an old bike i am riding for utlility, I dont have the skills or tools to completely dissassemble the bike and paint the entire frame myself and have it look nice, and i didnt want to incur the expense of paying my mechanic to dissessemble the bike, send it out to get powder coated, and then reassemble.

I dont even think i need to paint over the primer coat, even though the primer coat is not designed to be a top coat, but i am open to thoughts on that.

I figured id leave it with the primer exposed for awhile maybe over time i will get more skilled and get some more tools and then want to disassemble the bike and then try to spray paint the whole bike or send it out to get powder coated, so i thought id leave it just primered right now because there's no exposed metal. If the primer coat deteriorates i can spray it again.

I was debating on getting paint in cans and using brushes, v. spray paint cans but i figured the spray paint is easier (the non-spray paint cans dont come in small sizes for primer, and i didnt want to have to deal with buying and then cleaning brushes (you need mineral oil apparently.)

I used masking tape to mask the areas around where i wanted to paint but didnt do such a neat job. So on my other bikes i am figuring maybe i will try brushing instead, i figure I can spray some of the paint from the spray can into a little cup and then brush the paint on, since i am just painting small areas anyway.

I dont have a digital camera so dont have any photos.

I havent seen any threads discussing this particular approach of using primer as a quick way to avoid/cover rust on old bikes (as opposed to people restoring bikes they really care about the appearance of, ie special vintage bikes) so i am posting my experience and seeing what anyone else thinks.

One of my road bikes is a 1983 Specialized Sequoa which i got relatively cheap recently that has some small areas of rust. My bike mechanic and the owner of a good bike store both told me dont mess with any attempt to partially repaint this bike because it will ruin the collectibility (my mechanic said maybe its worth $350 which isnt a fortune). On other hand i dont like riding around a bike with rust that has exposed metal rusting, that will only get worse. I feel id rather do a amateur primer paint job to cover the exposed metal, remove the surface rust, than leave it as is (or spray a clear coat with no attempt to remove rust.) This protects the frame better. With the Specialized bike, i am thinking maybe later on i will pay to have the parts all removed and send it out for powder coat and pay to have the parts put back on, but i dont want to incur the expense now. If i am going to get it powder coated theres no harm in my spraying primer on now as a temporary measure and it protects the frame.

Keeping a bike frame stock as is for collectibility purposes that is rusting (slowly in small areas) make little sense to me. Any thoughts id like to hear.
If it was some very valuable italian vintage bike maybe the resale value is impt but i got the Specialized to ride.