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I ride my bike in all weathers, and I'm concerned over the possibility of rust forming inside the frame and going undetected.

I can't easily obtain FrameSaver or the like, so I'm thinking of dropping a packet or two of silica gel desiccant inside the seat tube of my steel-framed bike. I'm concerned that its effect won't last as long, or that it will be rendered ineffective should a small amount of water pool inside my frame after riding in the rain, soaking the gel packet.

Does anybody have any experience with using silica gel packets to prevent corrosion? Does it do a comparable job to corrosion-preventing sprays?

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3 Answers

up vote 4 down vote accepted

No, it wouldn't work as long as the frame is not hermetically sealed to keep water from entering (I don't know why manufacturers don't do that).

The silica gel can only absorb a tiny quantity of water, a drop or so per packet, then it becomes ineffective. It is only effective to absorb water vapor.

You can bake it in the oven to regenerate it. If you want to play with it, there is a version with a water-sensitive dye (blue -> pink, now illegal because of cobalt content) and orange to a bit less orange. If left open, it will change color quickly.

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Frame manufacturers don't hermetically seal the tubes because hot welding gases need to escape during the manufacturing process. –  Stephen Touset Aug 26 '12 at 22:31
    
They could leave a hole open and then plug it at the end. But in general corrosion does not seem to be a big problem to warrant that effort. –  Dan Aug 27 '12 at 4:34
    
An additional note, there are so called vapor phase/volatile corrosion inhibitors. I really don't know if they are used on bike frames, but they are very cheap. Steel parts typically come in bags treated with that stuff, and tools are often kept in a drawer with a rag dipped in the inhibitor. I don't know a trade name, but here is one product that I found. lg-outdoors.com/proddetail.asp?prod=GA_REM18378 –  Dan Aug 27 '12 at 4:39
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What the other Dan said, plus if you drop the stuff into your seat tube it will end up in the bottom bracket housing and muck up your BB bearings.

It is quite unusual for frames to rust through anyway (I've only seen it on frames that have been left in the weather for years, if not decades), and if you're that concerned you can remove the BB and headset bearings and give the whole inside of the frame a good blast with WD-40 once or twice a year.

Someone who's really a fanatic could figure out how to coat the inside of the frame with auto undercoating, but that would add considerable weight.

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I had planned on hanging from a string from my seat post, but if it's going to be useless for more than a small quantity if water I guess that's not a great solution. –  meagar Aug 26 '12 at 19:25
    
I wouldn't trust the string -- it's apt to break and just wrap itself around the BB shaft. –  Daniel R Hicks Aug 26 '12 at 20:46
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It is not so easy for the water to get inside the frame, and fortunately in this case, the oposite is also true: it is easy to keep it out. You can use hot glue to cover a bunch of tiny holes meant to let fumes out during the welding of the frame. These holes are usually near the extremes of the seat stays or chainstays. Hot glue won't stick too hard and wont damage paint. Can be removed by just the fingernails.

The other tubes do not require these holes as they connect to some other. Top Tube for example has ventilation trough a hole in the seat tube (remove the seat post to check if it's there) and the headtube. The same for the downtube, it comunicates to the headtube and the bottom bracket shell. This limmits the water entrance posibilities to the bb bearing, the headset bearing and the seat tube collar.

Good bearings correctly installed should have seals that avoid water getting inside them, and also keep it from geting into the frame.

The lower end of the steer tube is most of the time open, you can seal it by using a cork or a similar rubber snap-in seal...

For the headset bearings there are comercially vailable neoprene or rubber sleeves, but you can make do with ol inner tube of an apropriate size that fits tight (For the top bearing: just remove the stem, slide the rubber and replace stem.)

Similar thing can be done for the seatpost collar, the short cut usually towards the back of the bike collects water and debris thrown by the rear wheel. It can be protected with either commercially available neoprene sleeves or with old inner tube. If you can't find a tube that fits tight you can lessen it's diameter by cutting it and gluing with vulcanizing compound (a.k.a. patch glue).

Some frames have unused screw holes for accesories like water bottle or the like. Cover these with correct boltls or hot glue. There are also plastic plugs for this purpose (if you can get hands on them), some of wich resemble bolts.

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