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I have a beater commuter steel bicycle that is subject to all kinds of weather, abuse and a lots of scratches. Several hot-spots on the frame have appeared over the time where most of the damages and corrosion happens.

I was thinking of protecting those spots by:

  • removing rust
  • applying a layer of 2 component epoxy (have G-flex at hand) to seal the steel
  • after epoxy cures, wrap it with self adhesive silicon tape to protect epoxy from UV exposure

Does this sound like a good idea? Some better, cheaper, quicker, more durable solutions?

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That sounds ok, just don't cover any of the weep holes (the ends of your stays, bottom of the fork, near brake bosses...). Water will get inside of the frame no matter how vigilant you are, so plan on a biannual tear-down in order to dry out and spray the insides of the tubes with frame-saver or another corrosion inhibiting product. You can do this with some of the components still on the frame (headset cups, derailleurs, drive-side BB cup) but you'll want access to the head tube, seat cluster, and BB shell. –  WTHarper Mar 20 '13 at 15:14
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I'd just have a bit of touch-up primer from an auto parts place. You can buy it in a bottle with a brush in the cap. Primer will bond with bare metal better than anything else. For rusty metal there's even a "rust converting" primer that is quite good. –  Daniel R Hicks Mar 20 '13 at 15:38
    
Being a beater implies looking like a beater. Painting the bike to make it beautiful doesn't sound "right", so as to spend a lot of time, money and effort to "protect" it. That said, touch-up with auto-primer and similar stuff, as said by @DanielRHicks, seems to be the most sensible solution. –  heltonbiker Mar 20 '13 at 16:45
    
To clarify, I wanted to use epoxy on parts of the frame where paint just does not last, in places where there are too many scratches from u-lock, locking chain, and what ever. I hope that epoxy on those spots will last longer than paint. –  Davorin Ruševljan Mar 20 '13 at 23:27
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On my beater I just rub some grease into any exposed bits of steel every few weeks. Takes seconds and lasts quite well. Don't leave it too greasy though, or you'll get it all over your trousers. –  alex Mar 21 '13 at 1:04
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3 Answers

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If this is a beater bike then I think the 2 component epoxy and adhesive silicon tape is probably going overboard. Steel is very resilient compared to many other frame materials so little scratches, dents, and dings are unlikely to cause much harm. Obviously the downside to steel is that it's prone to oxidation (rust) and needs to be protected.

Externally I would just use touchup paint as necessary. If it's a fresh scratch just slap the paint on there. If it's an older scratch use a fine grit sandpaper to spot sand the area and then apply the paint. That should be sufficient for maintaining the exterior of the frame.

The interior of the frame's tubes are a different story. They are unpainted and unprotected from the elements, and this can be bad for a beater bike as it probably sees more of the elements than your other bikes. For the interior I recommend that you get a can of Frame Saver and apply it to the inside of the tubes that make up the frame. After the propellant evaporates, Frame Saver leaves behind a residue that is very similar to the industrial packing grease that you fine on steel or iron parts when they are new. It shields raw steel from the air and moisture that can cause oxidation. It's worth noting that it also makes a horrible mess, so lay down a bunch of cardboard and apply the stuff outside.

Strip the bike down to the frame. Removing the fork, cranks, and seat tube are most important, but you'll be swinging the bike around in all different directions so strip the wheels off the fork and frame as well. Youll have access to the inside of the toptube and downtube through the seat tube and headtube, and bottom bracket. Spray liberal amounts of the stuff in all five mentioned tubes. If you don't have access to the seat stays and chain stays through the seat tube and bottom bracket there will be little breather holes- likely located at the dropouts. Spray plenty up in those four tubes as well. If the seat stay bridge (where your rear brake attaches) has the same little holes in it, then spray some in there, too, though it won't take much. If the bridge doesn't have holes to access it, dont worry; the framesaver will make its way in there via the seat stays. If there's a chainstay bridge, do the same thing you did with the seatstay bridge. Now you've squirted plenty of Frame Saver in every tube of the bike, right?

Now, while the Frame saver is still flowing, you want to tilt and shake the frame in every direction to ensure that it covers the inside of all the tubes of the bike. While it's wet (before the propellant/thinner has evaporated) Frame Saver has very low surface tension and viscosity. Shaking and tilting the frame is crucial in achieving full coverage, but it will also flow on its own to help cover any spots that might have been missed. This process is somewhat time sensitive, though, as once the stuff sets it's not going anywhere. Some will leak back out and this is expected. Remember how I said you should do this over cardboard outside? Hope you were listening, because Frame Saver is not easy to clean up.

Let's not forget about your fork. You should be able to access the inside of the fork legs with the same little breather holes that were on the rear half of your bike. Follow the same procedure above. You might want to get the inside of the steerer tube as well, and the outside of the steerer should be coated in a light grease to boot. If you're feeling really paranoid about corrosion, you could even do the inside of your handlebars and seattube. Probably not necessary, though.

Ok! Now let the frame sit overnight so that the stuff that needs to evaporate can do so and reassemble your bike. Between paint and Frame Saver you should have 99.9% coverage on the surfaces of your frame and fork that are exposed to air. Happy beating around town on your bike that is now impervious to the elements!

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Even though it's a "beater bike", I'm guessing you really want to keep it around for a while. If that's the case, I believe the best protection for it would be to paint it.

Strip the frame down (take all the components off) and thoroughly wash it.

If you want to do the job yourself, sand the frame down to remove any rust spots. If you have too much rust and you think epoxy might be in order, you can do that - but I suggest being extremely cautious at that point. If the rust incursion is that bad, you may very well have structural damage that could cause a nasty crash - or worse.

Use "Frame Saver" and spray the inside surfaces of the frame down with a liberal coating while it has been disassembled. Clean the surfaces again, Use rubbing alcohol to remove any oily deposits.

Use a quality exterior paint.

Alternatively - almost any autobody shop that has a paint booth can paint the bike for your fairly cheaply. They might even have sand blasting facilities/capabilities to make cleaning the metal easier. If you don't care about the color - just have them paint it when they do a regular paint job - and it'll be even cheaper since they don't have to clean their paint guns for a tiny batch color job for the bike.

Smaller/independent shops will tend to be a lot more willing to work with you on a project like this. The big shops tend to not be too friendly to "side jobs" like this.

I've had steel frames completely stripped via sandblasting, and professionally painted with powder coating, including two layers of protective clear finish, then baked in an oven for 2 hours. The cost was $130.

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I've heard of and seen many frames that suffer from poor quality powder coat paint jobs. Usually, you get what you pay for. –  WTHarper Mar 20 '13 at 15:18
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It's often not worth getting a beater bike professionally painted as the paint job costs more than buying another used bike. Even with harsh conditions, the bike would probably last 3-5 years without the paintjob, and a new paintjob would probably get quite a few scratches before the end of the first year anyway. –  Kibbee Mar 20 '13 at 15:34
    
This is very informative answer, but I am looking for some protection for critical spots, that will be more resistant than paint (if such exists). Also $130 is significantly more than I have paid for the whole frame. –  Davorin Ruševljan Mar 21 '13 at 10:57
    
@DavorinRuševljan: That's the price in US, I guess. Over here in Serbia you can have the same job for under 50EUR, I guess the prices are similar in Croatia. Basic sanding and painting is even less. –  Mladen Jablanović Mar 23 '13 at 18:29
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After some more investigation I have found 2 more interesting options:

  • Helicopter tape (Clear protective urethane self adhesive film)
  • Plasti Dip
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