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mtbdad67
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I found a loose spoke on my bike while cleaning it this past week. Upon further examination I found the head corroded off of the spoke. The spokes are straight pull aluminum that thread into the hub. They are mated to carbon rims. I am hearing this is a common problem. The wheels are just 18 months old. I have the same spokes laced to an aluminum rim that is 8 years old that have been bomb proof. Is anyone else having the same issues with this???? Yellow Liquid Ruler Grey Measuring instrument
 

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I remember a few years ago there were problems with a new fleet of helicopters operating in the North Sea, out to the oil rigs. The tail rotors were made of carbon but they had an alloy wear strip on the leading edge. There was some sort of reaction between the carbon and the alloy which caused the alloy to corrode and the strips came off, which caused the rotor to unbalance and fail. Which wasn't good.

Can't remember the exact details bit it was something about the carbon and alloy not playing nice.
 

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The issue with using carbon fiber and aluminum is that carbon fiber is electrically conductive, making the interface more susceptible to galvanic corrosion
 

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I encountered the same problem a few months ago with my Derby carbon rims and alloy nipples (my spokes were steel). After about about 5 years of excellent, problem-free service, I noticed a few loose spokes in my rear wheel and quickly learned (much to my dismay) that my aluminum nipples were severely corroded. The nipples on the front wheel also showed signs of significant corrosion but were in were in much better shape. I certainly could have "created" the issue by allowing sealant to leak past the tubeless tape and into the rim. I had the wheels rebuilt with new spokes and brass nipples. So far, so good.
 

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Same issue with an aluminum IBIS rim. The nipples are aluminum and they just do not last.
 

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Elitest thrill junkie
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I have good luck using some anti-seize as a barrier, putting it on the nipple surface in the rim as well as in the spoke threads. I have had a few corrode over the years, like 2-3 on 6 wheelsets, but nothing compared to wheelsets I've built that I didn't do this with. If the CF is coated, this also significantly reduces the problem. All nipples should be anodized, which also reduces this. I know it brings up the question of how all the other nipples are, but de-lacing and re-lacing seem to confirm that the issue isn't as big doing this, still, it's a good idea to figure in to replace the aluminum nipples on a carbon-rim wheelset every few years. Aluminum nipples with carbon rims do have this pitfall, but still build light and generally reliable wheels.
 

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The issue with using carbon fiber and aluminum is that carbon fiber is electrically conductive, making the interface more susceptible to galvanic corrosion
http://thecartech.com/subjects/machine_elements_design/PREVENTING_ELECTROLYSIS2.htm

thecartech.com said:
Electrolytic Corrosion (Electrolysis) occurs when dissimilar metals are in contact in the presence of an electrolyte, such as water (moisture) containing very small amount of acid. The dissimilar metals set up a galvanic action those results in the deterioration of one of them. The following is a list of the more common commercial metals, sequenced according to what is known as the "Galvanic Series".

THE GALVANIC SERIES

1- Magnesium
2- Zinc
3- Aluminum
4- Iron
5- Steel
6- Nickel
7- Stainless Steel 400 Series
8- Tin
9- Lead
10- Brass
11- Copper
12- Bronze
13- Stainless Steel 300 Series
14- Silver
15- Gold

When any two metals in this list are in contact, with an electrolytic present, the one with lower number is corroded. The galvanic action increases as the metals are farther apart in the Galvanic Series. It is not always true that there is greater corrosion the down the scale one goes. In certain cases one metal immediately following another may be very corrosive.
Spokes are 300 series stainless by the way, so an Aluminum nipple loses in the game.

Spilled sealant is probably more of an electrolyte than water, so I imagine that can be an accelerator.

I can't explain the carbon rim contribution exactly, but I imagine it could enable the flow of electrons around the wheel.
 

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I can't explain the carbon rim contribution exactly, but I imagine it could enable the flow of electrons around the wheel.
Ah... google is my friend.

Turns out carbon fiber is even farther down the table than stainless steel..

So the an answer could be to use nipples made of a material farther down the table.

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are there any spoke nipples that are -hard anodized- aluminum ? specifically hard anodized...as HA aluminum is not electrically conductive. I wonder if HA alum nipples in CF rims would make a difference ...
 

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Shoot - looks like I'll need to replace the nipples of my brand new wheels anytime in the mid-term future. All aluminum on carbon. I even put some grease to allow to lower the torque on some of them, but isolation will be really poor.
 
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