Had an almost new mtb bike come in for a tuneup and other minor work today. It was almost new but had sit in 10 inches of water for a few days in a flooded basement. Surprisingly, the grease in the BB pretty much kept the water out. But both the front and back wheels ended up being replaced.

The issue was the spokes. This was a relatively inexpensive Norco Scrambler and the spokes were SS. Well sort of. They started breaking as soon as I started checking tension by squeezing them with my hands. Not at the ends, but in the middle. On fact it was impossible to BEND the spokes - they just broke off.

Close examination of the breaks showed crack-like fissures of corrosion deeply penetrating the spokes at the failure points. First time I've seen anything like it myself. Not an isolated incident either as the spokes in question could be broken like glass rods at about two inch lengths.

Burton, Any idea what brand of spoke? I've never seen anything like it and I'm interested in more knowledgeable replies.

Brad

I have the remains of a number of spokes with the identical problems. I'm surprised you see this under the circumstances you describe because it's characteristic of chlorine damage. Search for chlorine damage in stainless steel and you'll find lots of links describing the phenomenon. Basically the chlorine ions enter the steel's crystal structure and render it weak and brittle.

On my wheels, spokes would snap with a pronounced ping while the bike was just sitting there. Mine better fit the profile in that these bikes were in Cozumel, and exposed to sea water and salt air 24/7/365. When I examined them the spokes were full of inclusions (3-5 per spoke) so I had to rebuild both.

I was first made aware of the issue by my dentist who hoped I could help him solve a problem with sterilization of his tools. The autoclave (steam) dulled them quickly, but repeated sterilization in Chlorox made them brittle and tips would break off without notice, something that could be serious in his line of work.

Anyway, most grades of stainless used for spokes are moderately resistant to chlorine damage, but some spokes made in Taiwan a few years ago were quite vulnerable. These made their way into the OEM pipeline ended up on a number of new bikes (including the pair I sent to Mexico) a few years back. I'm surprised to see the problem is back.

What FBinNY said leads me to wonder if these were Hsing-Ta's:

https://www.mrrabbit.net/docs/spokeheads/main.html

They usually have the wiggly star on the head...these are about as cheap as you can go in terms of stainless steel spokes. Bottom-line grade and lighter than most stainless steel spokes as well...

=8-)

Very interesting. I've never seen or heard of anything like that. Thanks for presenting the topic, and thanks to FB for explaining it.
Maybe another good reason to stick with the leading brands when it comes to spokes?

It's possible, I'll check the spokes I still have left (I hope I saved a few heads). Anyway one of the frustrations in choosing stainless steels is that those with the best chemical properties often have lousy mechanical properties, and vice versa. The 18/8 and similar alloys commonly used in quality spokes are not the most corrosion resistant (though they're not terrible), but the marine grades don't make sense for spokes.

It's possible that even quality spokes can suffer this kind of corrosion damage if submerged in a chemical soup long enough. the mechanism of corrosion resistance isn't through and through, but more of one whereby the steel forms a protective oxide skin (similar to how aluminum does it).

About 15+ years ago there was a run of poorly made SS spokes. Many manufactures were affected, thousands of wheels. Spokes broke along their mid sections. The only clue was spots of "rust" or blackened something. The big brands honored silent warranties. Over a number of years I probably replaced dozens of wheels alone.

It seems that the spoke plague has not died. Andy.

There may be lots of that old stock still circulating around out there too, particularly from on line sellers.

The 18/8 (AISI Grade 304) stainless steel FB mentioned is used by most high quality spoke manufacturers and is very corrosion resistant EXCEPT to chloride exposure. I does indeed suffer from chloride embrittlement. "Marine Grade" stainless is usually the much more expensive 316 or Monel, which isn't a steel at all but a copper/nickel alloy.

While 18/8 isn't a marine grade it normally does OK even in coastal areas and when exposed to salt water intermittently. The type of chloride attack I've seen and the limitation of the issue to certain batches or brands of spokes indicates that something else is going on. Either a slightly different, and more vulnerable grade, or possibly a process error, such as failure to pickle and passivate the finished product to form the resistant skin that stainless steels need.

The experts I consulted at the time, said it wasn't the type of damage that not passivating would cause, but maybe not passivating increases the vulnerability to chloride attack.

This (fortunately) is not a common problem, but as Andrew S. pointed out, when it a bad batch of spokes is produced, it changes from rare and isolated to almost 100% failure.

When my daughter was living in Chicago a friend gave her a cruiser that has alloy rims and hubs and stainless spokes. After she moved back here she noticed a broken spoke and brought it over for me to repair. The spokes were pitted and most broke when I put a spoke wrench on them or bent them a little so I replaced them all with DT's. It's been a couple of years and I don't remember the brand.

Thanks for the replies everyone. No idea what brand of spokes they were and nothing is detailed on the Norco site. Will put a few aside and see if there are any identifying marks on them, and will be contacting Norco just to give them a 'heads-up' anyway.

Curious, any idea if this is an older bike or fairly current model. As Andrew pointed out, there was a rash of this some time back in the late nineties, but it's been or almost unheard of since. I wonder if we're possibly looking at another episode.

Going back to Burton's OP, I wonder if the spokes he was dealing with were actually stainless or just cadmium plated carbon steel. Cd plated or galvanized spokes corrode badly once the Cd or Zn coating is compromised and perhaps that's the problem.

I doubt it. First of all Burton's no newbie, and I'm sure he can recognize SS spokes vs. plated. But more important, carbon and alloy steels would have rusted in the classical way, vs the type of brittle inclusions you see in chloride attacks on stainless. This is a unique phenomenon and doesn't happen to most non stainless alloys..

I first hear of in a different context when I dealt in ultrasonic cleaners. When dentists started cleaning their instruments in Clorox using ultrasonic cleaners, suddenly there was a rash of Stainless steel basins turning porous. My ultrasonic vendor sent out letters warning of the problem, and specifying that use of any products containing chlorine directly in the unit would void the warranty.

I know it's been a couple of months since you guys have posted in this thread but I wanted to add my two cents. I purchased a 5 gallon bucket of chlorine tablets for my pool about 1 month ago. The bucket was sealed, so I left it in my garage, next to my mountain bike, for about 3 weeks before moving it outdoors. When I got my bike out last night for a ride, the rear wheel was warped and I noticed I had two broken spokes. There appeared to be a rusting/ pitting on all the spokes right around the area that would have been right next to the lip of the 5 gallon bucket. I pulled my wheel off and headed to my local shop. On the way, with the wheel in the back, I hear an extremely loud pop. When I got to the shop (and yes, I purchase all my bikes and gear at local shops!) there were two additional broken spokes! Before I could say anything, the tech asked, "do you have a pool?"...exactly! So a word of warning, it happens fast and it happens even if you think the package is sealed. Had I been riding when they went......

This is exactly the case on my rear wheel. A spoke even broke when truing the wheel after replacing one of the other broken spokes. I bought the bike in about year 2006 or 2007, so it was not fifteen years ago as Andy mentioned. I still use the same wheel with about seven spokes replaced. I broke a spoke as recently as a few months ago, so it is still an ongoing problem. I will have to do something about it as I have put on weight and therefore put a larger tyre on the rear (28-622), which means there is less room for a tacoed wheel to go through the chain-stays on the frame. Also, no two spokes on the wheel sound the same when plucked. The bike-shop I bought it from was owned by a friend and I did not have the heart to tell him to re-spoke the wheel at his expense in the early days or now. DG.

I read an interesting article about this a few years back. Someone wrote into a magazine asking why all of their tools and other metal items were prematurly rusting in the garage. The 'expert' said to remove all chemicals/fertilizers from the garage.

I bought 2 bikes today with this problem....the spokes are broken in the middle. I'll post up pics tomorrow and yes, they came from a garage with pool chemicals.

Even without pictures, I'll venture that there were small black inclusions and the spoke was super brittle (like raw spaghetti) there. This is classic chloride damage to stainless steel. It's fairly rare with spokes, but when it happens either because of poor process or material in spoke manufacture or exposure to certain chemicals, the damage is extensive and always fatal to the spoke.

I lived in Santa Monica for 9 years. I didn't own a car so bicycled everywhere: to and from work, shopping, in the mountains and along the beach. I never broke a spoke. I didn't have stainless steel spokes, just the cheapo stuff. Does chlorine hurt SS spokes but not the cheap kind?

Yes, it seems to be more or an issue with certain stainless vs carbon and alloy steels. It's also the nature of the attack, which cause deep penetration rather than the largely surface damage of classic rust. You can search Chloride damage in Stainless steel for plenty of detailed papers, but here's a short synopsis.

I should add, that the vast majority of stainless spokes are decently resistant to the problem. I keep two bicycles in Cozumel, MX and all 4 wheels suffered total spoke failure in 2 seasons. Since then, I've rebuilt and no issues of this kind in 6 years. Living in a harsh (salt air 99% humidity) climate, I'd much rather have SS spokes than plated, but it's important that they come from a good supplier.

316 is a stainless Steel. It is iron and 17-20% chrome and 11-14% nickel, 2-2.5% molybdenum.
Monel is a copper nickel alloy.
I have welded on both.

I have seen spokes with no stamp on the heads that were brittle like that. One set was on a cruiser that my daughter had in Chicago. The other was on a rear wheel on a friends adult trike.

Since this topic has risen to the top again, I'll ask: does winter salt cause this problem as well? I used DT Swiss spokes when building the rear wheel of my winter bike, but use a cheapie MTB front wheel so that I can sacrifice its brake track to the elements. Would a careful application of Frame Saver or some other kind of waxy oil (just to the spokes) be a good preventative measure, or not worth doing?

Thanks.