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Corroded Alloy Nipples on inside of rim


johanpre44

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Got a flat on my tubeless yesterday and decided today that I will take the bead of the rim and have a look at the inside. Not a big surprise that most of the latex dried out, but in the process of removing the tire I could see the rim tape also pulling away from the rim. To be safe I decided to pull the rim tape of completely and put on fresh tape.

 

What I have found is that some of the nipples seem corroded and some not, any idea why something like this would happen? I'm using Tire Juice (Sealant) and clean my bike with diluted Prepsol (which I've heard is not good for Aluminium and corrosion). I have found no corrosion on the rim.

 

Any suggestions for proper cleaning? I have used baking soda and a toothbrush (like you would do with corrosion on a car's battery which kind of looks similar).

 

Pics attached (not the best), first pic of a shiny nipple, second one you can see the white corrosion (interestingly these two nipples are right next to each other).

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post-43160-0-98527700-1440440967_thumb.jpg

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It is normal for alloy nipples to corrode over time.  Wheels with alloy nipples require a bit of extra tlc, especially if the wheels get wet occasionally which is pretty unavoidable.  You need to regularly oil the nipples, i.e a drop of thin oil on each nipple where the spoke screws in.

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Aluminium oxide corrosion forms between the nipple and spoke.  At some stage the nipples will crack or seize onto the spoke.  When you can't move them enough to true the wheel the solution is simple.  Cut the spokes and replace, using brass nipples this time.  

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I have a couple of sets of wheels with alloy nipples, just have to look after them.  and if they corrode I will just replace the nipples with new alloy nipples.  I am busy teaching myself to build wheels so should be more affordable to manage.

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I have a couple of sets of wheels with alloy nipples, just have to look after them.  and if they corrode I will just replace the nipples with new alloy nipples.  I am busy teaching myself to build wheels so should be more affordable to manage.

 

You know whats more affordable to manage... putting in brass nipples once the alloy ones corrode and never having to do them again? 

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No proof though but I suspect it might be the latex. All my Roval wheels had the same problem and then spokes started popping one by one. Maybe give it a squirt of WD40, stick on some new rim tape and hope for the best. Some of the spokes on my front wheel had to get cut off as the nipple seized on the spoke when I tried to replace all the nipples with brass ones.

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Aluminium oxide corrosion forms between the nipple and spoke. At some stage the nipples will crack or seize onto the spoke. When you can't move them enough to true the wheel the solution is simple. Cut the spokes and replace, using brass nipples this time.

Stainless steel spokes and alu nipples form a galvanic couple (like a weak battery) that will corrode the alu if it gets wet. This happens to a greater or lesser degree with all dissimilar metals in contact when wetted.

 

Brass and stainless forms a much weaker couple and thus corrodes more slowly.

 

You can retard galvanic corrosion by excluding water and or oxygen or using metals that are close on the galvanic table. A bit of grease or oil will help. Keeping it dry helps the most. Frequent washing is a good source of water. Salts (sea water) very bad. Dishwash liquid has salt in it btw so choose detergents carefully.

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You know whats more affordable to manage... putting in brass nipples once the alloy ones corrode and never having to do them again? 

Personal preference.  I choose to use alloy nipples.

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Quite worrying and what proportion of bikes have steel / stainless steel : aluminium combination as standard?

 

I agree with everything added here as I re-looked at some stuff from a structural application where the rubber washer between galvanised steel and aluminum had been left out; we hoped for a retro fit of some sort.  But there was nothing guaranteed; no Loctite or fancy anti seez that would work. It was "probeer weer".

 

It was insulation or galvanic protection, neither of which were viable and aren't on bicycle spokes either I guess.

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Quite worrying and what proportion of bikes have steel / stainless steel : aluminium combination as standard?

 

I agree with everything added here as I re-looked at some stuff from a structural application where the rubber washer between galvanised steel and aluminum had been left out; we hoped for a retro fit of some sort. But there was nothing guaranteed; no Loctite or fancy anti seez that would work. It was "probeer weer".

 

It was insulation or galvanic protection, neither of which were viable and aren't on bicycle spokes either I guess.

Yeah unfortunately the choice of materials in engineering nearly always involves a trade-off. Stainless steel is so good for spokes that we get forced to live with its effect on the hardwear at both ends.

 

I don't know if it is advisable to use an anti-seize compound on the spokes and nipples hen building a wheel but this would help for corrosion protection. Then, before fitting the rim tape I would also consider painting the top of each nipple (on the inside of the rim) with a dab of tectyl or similar anti-corrosive wax coating.

 

The inside of rims unfortunately is not easily sealed against ingress of moisture and then it does not dry out too fast either and this is why corrosion is prevalent there. Pay careful attention to rim taping because the ammonia in popular sealants can also corrode metals, brass in particular.

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Now this is very educational. Think I will do a bit of wd40 on the nipples from both sides before I add the rim tape again. Think I will stick to brass going forward, just hope the is some good life left in the wheel before a rebuild is needed.

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Now this is very educational. Think I will do a bit of wd40 on the nipples from both sides before I add the rim tape again. Think I will stick to brass going forward, just hope the is some good life left in the wheel before a rebuild is needed.

If you are going to use a corrosion inhibitor then preferably pick one that will coat the nipples and dry to a waxy layer (like tectyl 506 or waxoyl) Water repellent sprays like WD40 or Q20 that stay liquid might affect the adhesive on your rim tape if running tubeless.

 

Tectyl 506 used to be available in a spray can but I have not seen any for sale in a while...maybe newer products out there.

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Personal preference.  I choose to use alloy nipples.

 

I hope you enjoy building wheels.

 

Any particular reason you prefer alloy over brass, given that a properly built wheelset with brass nipples will last almost forever?

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I hope you enjoy building wheels.

 

Any particular reason you prefer alloy over brass, given that a properly built wheelset with brass nipples will last almost forever?

 

Thats exactly why I asked? Makes no sense! 

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