RiverHills

Just curious if anyone has ever heard of any issues with galvanic corrosion when using brass nipples with aluminum rims. Brass of course contains copper which does not play well with aluminum.

Kimmo

It can happen, but it's usually not a problem. Good wheelbuilding prep should keep it at bay.

You can always use eyeletted rims or ally nipples if you're really worried.

BCRider

The nipples are nickel plated. And that seems to be enough to prevent the problem. I know that I've never had any issues and you don't see dozens of threads about this "problem" because it just isn't an issue in the practical sense. The only time I've seem corroded in place spoke nipples is on really old rims. And then it's between the nipple and the galvanized spoke which were assembled at some factory without the benefit of any spoke prep or lubricant.

fietsbob

Might corrode, some , but not like bare steel and aluminum do
if you leave a stem and seatpost in a bike for decades.

RiverHills

Its been so long since I had to change a flat tire (knocking on wood) that I can't remember how exactly the nipples are attached to the rim. Is there direct contact betweent he nipple and rim, is there a bushing, or is it typically greased?

HillRider

Brass nipples (Ni plated usually) are the standard for aluminum rims and have been used for decades and decades with no particular problems and are far stronger than aluminum nipples. The real corrosion problems seem to occur mostly with aluminum nipples due to water and salt exposure.

Nipples aren't "attached" to rims. They sit in the spoke holes and are retained by their wider heads inside the rim and, yes, they have direct contact with the rim. Some rims have reinforcing sleeves lining the spoke holes and some don't but they are there to strengthen the rim, not prevent corrosion. Most wheel builders lube or treat the spoke threads to prevent wind-up during tensioning and to prevent later corrosion but they usually don't lube the nipple heads.

Mark Kelly 

Not really.

In normal conditions the oxide layer on the aluminium is a good enough insulator to prevent the cell from forimg.

MNBikeCommuter

Yes, corrosion is a definite possibility in a salt environment, as mentioned. I retired a set of "summer wheels" with 53k miles on them with no corrosion problems; a fair number of the (Minnesota) winter set's nipples were frozen when I tried to replace the rims at 12k miles.

HillRider

That's pretty much a universal experience. In dry conditions, wheels will last until the brake tracks wear through or you hit something hard enough to bend them.

In a wet, salty environment (Pittsburgh too) wheels wear out from abrasion and corrosion a lot faster but it's not because of brass nipples. Aluminum nipples are even worse under these conditions.

RiverHills

Yeah, the aluminum nipples really seem to corrode faster than the brass, which is interesting. I know that if ACQ pressure treated wood comes in contact with aluminum flasing, it doesn't take long before the copper in the ACQ trashes the aluminum. I was curious why this doesn't happen when brass nipples are used with alu rims. Then again with bikes it seems to be common to combine dissimilar metals.

Kimmo

There's usually nothing, sometimes washers or grease.

The plating does a good job on its own though; the washers or grease are mainly to help with tensioning the wheel.

joejack951

Corrosion isn't a very intuitive topic. So much depends on what is next to the metal in question. I worked in the marine industry for some years and did a lot of corrosion testing. We could salt spray test a 303 stainless steel fastener and not see any hint of corrosion. Put it in an assembly with some cast 316 stainless parts and it rusts terribly. Brass will tarnish (turn green) in the presence of salt water but will remain virtually unaffected if plated with nickel first. Likewise, 6061 aluminum will develop a powdery white corrosion when left bare in a salty environment but will not show any signs of corrosion at all with a proper anodized finish. Even really good stainless steel (billet 316L) will shown corrosion if not passivated after machining.

I think the issue with aluminum nipples corroding has much to do with the anodizing process not doing a great job deep inside the thread portion of the nipple. This is compounded by sitting next to a stainless steel spoke. The bare aluminum is a far easier target for corrosion (see chart here: https://www.corrosionist.com/galvanic...sion_chart.htm) and gets sacrificed first.

RiverHills

Good discussion here guys. Thanks for the info.

FBinNY 

No, the nickle plating and anodizing seems to prevent that, but you're not out of the woods if you ride in wet conditions with non-eyelet rims

Rims are anodized before being drilled, so the sides of the spoke holes are bare metal. While I've never seen the nipples react with it, water wicks into the gap between the rim and nipple carrying it salts and acids. This attacks the bare aluminum, causing it to oxidize and swell. The first effect is that it jams the nipple making future alignment difficult or impossible. Over time further corrosion causes stress cracks to form at the nipples, and in extreme cases can cause rims to form cracks connecting holes and splitting.

After building, put a drop of something like Boeshield or LPS-3 at each spoke hole and spin the wheel to drive it in. You might want to replenish it once a year or as needed if you're an all weather, all season rider.

joejack951

I'm an all-weather rider in a place that likes to use a lot of road salt in the winter. I'm in the process of rebuilding my front wheel which suffered a cracked flange (posted on this a while back and just getting around to fixing it. Spare wheels are nice to have). It was built with aluminum nipples and aside from one which was completely frozen, they survived 10,000 miles of commuting just fine. The worst corrosion was seen on the rim (IRD Cadence) where it's drilled for the Presta valve. All the nipple holes are eyeletted which seemed like it did a decent job of keeping the corrosion out. That was a bit of a surprise to be honest. The eyelets on my Mavic Open Pro rims corroded pretty badly with far less use.

Al1943

I use DT Swiss aluminum alloy nipples on all of my wheels and have never had a nipple fail. My wheels are not exposed to salt water except for occasional sweat drops. All of my rims have eyelets, Open Pro, DT Swiss, etc., and so the nipples are not in direct contact with the rims. Some "experts" say that Aluminum alloy nipples are actually stronger than brass but I don't know how that could be proven without knowing the exact alloy used.

noglider 

Aluminum nipples don't solve any problems unless people think of you as smart. They'll cure that condition.

Al1943

After 15 years of building wheels I've not had one problem of any kind with aluminum nipples, and still have the earliest wheels.

noglider 

Ok they work for you but what problem do they solve? Sorry, I'm not calling anyone stupid. Didn't mean to sound like that.

HillRider

As you noted, you don't ride in wet or salty conditions and that certainly aids wheel longevity.

joejack951

Simple, like many bicycle related "upgrades" they are lighter than the alternative. For those wanting something flashier, they are also available in colors.

Let he who owns only the heaviest bicycle components cast the first chainring at the weight weenies (a steel one of course)

Al1943

Brass nipples are also available in colors.
I'm certainly not a weight weeny but I do know how much more fun it is to ride these Oklahoma hills with relatively light weight wheels, especially when I'm trying to keep up with my friends, many of which are several years younger than me. My heavier 57 mm deep profile aero wheels are now "wall art" in my garage. My road wheels have 32 spokes on the rear and 28 or 32 spokes on the front.

noglider 

If lighter by a tiny amount is better, then they are better. If the problems they cause are worth it, then they are better (for you).

But they don't solve an actual problem. No one ever lost a race or couldn't climb a hill for lack of aluminum nipples.

joejack951

Do you use all steel chainrings on your bikes?

FBinNY 

I guess we can alloy nipples to the list of things that folks get over wound up over. This is starting to sound like a chain lube discussion.

The obvious benefit of alloy nipples over brass is lower weight. The only real drawback if the spokes are the proper length is higher cost.

Strength isn't an issue because either is up the the task. I build with alloy or brass nipples and have never had a nipple failure with either, nor have I ever seen a nipple failure with either that wasn't because the spokes were too short, in which case I've seen both fail.

I prefer not to use alloy nipples for the simple reason that they're slightly more prone to rounding with regular slotted spoke wrenches. That means I need to use the box type of key sooner as the wheel comes to tension, slowing me down. Also with dark colored nipples there's more risk of cosmetic damage if a spoke wrench slips.

Other than that alloy nipples are perfectly fine and sound if one is willing to pay the added cost.