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I noticed rusting screws at a ~ 1 year old bike and rusting screws at another bike after a few months, where the screws were part of a replacement (front gear ring package).

Both bikes were usually placed in rain protected places when possible.

Thus the question: Is this normal? Or do I have to change my bike dealer?

I mean, are not stainless screws standard? Or are they too expensive?

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Reading your question I'd say your title would be more descriptive if it was something like: "Are rusting screws a sign of cheap/bad material?" –  jilles de wit Oct 27 '10 at 11:09
    
@jilles de wit: You are right, I'll rename it. –  maxschlepzig Oct 27 '10 at 15:28
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3 Answers 3

up vote 10 down vote accepted

Stainless steel is rust-resistant not rust-proof, especially if the bike sees the outdoors a lot, it isn't uncommon for screws to get a fine sprinkling of brown spots. The good thing about screws is that they can be easily replaced.

If you were very enterprising you can probably replace all your screws with titanium ones, they are slightly stronger than steel and are less temperature dependent (not that any of this really matters on a bicycle) and are fairly resistant to corrosion AFAIR a little more so than stainless steel.

Painted components (like your bike frame) are naturally rust resistant because the paint prevents contact with oxygen, which means that the metal can't oxidise and also explains why its not a bad idea to touch up on large paint chips or scratches with touch up laquer.

ADDED a quick wikipedia glance explains that while stainless steel gets covered in rust, unlike regular steel the rust is passive meaning that it will just stay there (looking unsightly). With regular steel, rust has the nasty habit of eating away at the metal (it is an active oxidation site). The rust on stainless steel behaves like a coating that prevents further oxidation.

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Rust on stainless steel can also act as a theft-deterrent coating! –  Jefromi Oct 29 '10 at 14:16
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This is fairly normal. Many of the screws are are stainless but where you use the hex key on them they still rust. My best guess is that this is because you scuff the metal when you remove and put them back in.

I'll also mention that this happens on whitewater kayaks. Again typically in the places where a screw driver has touched the screw/bolt.

To my understanding stainless steel is a trade off between stainless and strength. The more stainless it is the weaker it is and so on.

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Probably not from scuffing the metal -- probably from leaving a small deposit of other metal (e.g., from the screwdriver blade) embedded in/stuck to the surface. Contact between dissimilar metals (and other electrically conductive materials) increases the chances of corrosion. –  Jerry Coffin Oct 27 '10 at 6:04
    
Not exactly weaker, but more brittle... –  Brian Knoblauch Oct 27 '10 at 15:06
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Is your frame aluminum?

It is worth noting that, due to the differing electrical properties of different materials, oxidation (rust on steel) will occur much more quickly when dissimilar metals are joined. On an aluminum bike with steel hardware, electron transfer between the aluminum and the steel will encourage more-rapid-than-normal deterioration of the steel. Aluminum will continue to look great--actually protected somewhat by the transfer of oxidation to the steel. This isn't an uncommon issue. The U.S. Navy just got done replacing an entire class of destroyers that were built with steel hulls and aluminum superstructures--it's a problem that we sometimes accept as a tradeoff. It is, as other respondents have said, easy to just replace a few bolts every now and then. Steel bolts are much stronger than aluminum bolts! But the aluminum frame is plenty strong and is SO MUCH lighter than a steel one.

The rusting probably has little to do with the quality of your bike shop.

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Good point, in my case it is a steel frame. Regarding aluminum frames: I've always assumed that they are not much lighter because they have to be constructed with bigger aluminum pipes. I remember that some bike dealer told me something similar when I asked him about this some time ago. However, I am interested in more details about this - if I can't find a question here about this I will post it as a new one. –  maxschlepzig Nov 7 '10 at 20:20
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