"[304 stainless steel] is not recommended for outdoor use", Book of EN 959:2018 Chapter 7 Verse 2 (footnote)

Being called out for supplying 304 stainless steel hangers in 2026 citing the holy texts of EN959:2018 & gold-standard UIAA 123 is fascinatingly complex.

It's well-known 304 stainless steel has been popping up as the primary culprit of anchor/bolt failures in corrosive environments. And now with the latest chemical analysis of the sample on Kalymnos, a circumstantial 316SS.

Has the title of this post been already discussed in other threads? Yes:

316 vs 304 stainless steel rock anchors

SS 304 vs 316 longevity

Why is 316SS stated to be the minimum for outdoor use in the appropriate environment?  Because 316 is a lot more resistant to the failure modes of 304. Understood.

So if one has the funds, access to, and desire to follow current rock anchor standards to the T, then yes, do so, it's "best practice". 

What is NOT particularity discussed in the the EN & UIAA standard is the data, discernment, and known environmental factors to deem 304 acceptable for particular environments. E.g. The decades that 304SS bolts have served in non-corrosive dry inland areas, and still continue to serve w/o observed degradation.

To get guys to wean off plated-steel bolts, going 304 is a progressive step. But to expect to leap to the other end & go for a minimum of 316, and even UIAA 123 certified rock anchors only...well... the world collectively still have a long ways to go.

If one takes "316 is the recommended minimum suitable for outdoor use; 304 is not recommended for outdoor use" as dogma, then the next stronghold position is that ALL routes in ALL outdoor areas WOLRDWIDE with existing 304 bolts must be replaced with 316 or titanium at minimum to be up to standard.

That means yanking out the 304 bolts (yes, even fresh 304 5-pieces in Utah, AZ, and Nevada's deserts for example) and upgrading them to 316.

Should the "304 is not recommended for outdoor use" be slapped on product pages and laser engraved on rock anchors like how the California's Proposition 65 warning is on everything? -- It's a lot cheaper than actual research/testing.

It's a pretty wild/funny concept to imagine 304SS that's serving just fine in a region with soft rock that actually weathers/erodes faster that the material life-span/service-life, and/or from wear-&-tear that needs replacement to due those factors, but still arbitrarily upgrading to 316 anyways. 

Just being a salty ranter. 

Let's focus on the positive progressive side of the matter.

On product pages for 304SS bolts and hangers, add the disclaimer (the OP of the IG comment shared with us): 

304 Stainless Steel: Suitable for indoor climbing-anchor use or specifically assessed low-corrosion environments only. Not recommended as general-purpose outdoor sport-bolting hardware. Do not use in marine, coastal, humid/sheltered, chloride-exposed, swimming-pool-adjacent, industrial, acidic, sulfide-rich, or otherwise corrosive environments. Where corrosion conditions are uncertain, use 316/316L or better, and in SSC/SCC-risk environments use titanium or UIAA 123 SCC-class certified hardware. 

Why?

A shared concern is "304 stainless climbing-anchor hardware should not be marketed in a way that allows customers to assume it is suitable for general outdoor sport climbing".

I agree, this is reasonable to do. What's your thoughts?

For the average bolter that doesn't stay abreast on all the current knowledge and best practice regarding bolting, perhaps the best is to have them spend their buckaroos on 316SS in the event they haven't "assessed corrosion classes, chloride exposure, humidity, seepage, sulfide risk, mixed-metal compatibility, or long-term inspection", etc. Lord knows already asking a bolter armed with a hammer to thud on rock to auditorily assess quailty, and use their eyes to determine bomber vs choss is quite enough as it is... (Gahh! I did it again...) 

I'll conclude with a quote from HowNOT2's recent July '26 newsletter:

Where else is publicly used life supporting infrastructure so unregulated as bolting???  Where else does a private person spend so much of their time, effort and money for other people to have fun?  So the fact people CAN bolt is wild.  The fact people DO bolt is wild.  Let's break those two down:

The litigation station - It's the last sacred piece of at least in the USA where “at your own risk” actually means something. A random person you don’t know put in hardware you know nothing about and you clip it and trust your life to it. If it comes out, you don’t sue them, you can’t sue the land owner/land manager. I believe that’s a good thing as we are already too litigious and it would stop most bolting activity which is mostly good progress for climbing. However, people will put in the cheapest hardware, or do it without knowing enough, or install it sloppy without checking it. There’s no checks and balance other than the super healthy form of communication: screaming at each other online.

The installation station - People bolt because… their egos! 

Giving credit to the UIAA/Safecom, DAV, Safercliffs, CragChemistry, HN2, + other organizations and the many developers/engineer/specialists involved, there's a lot of progressive good motives.

Things are getting better in the bolting world.

Suppliers of 304 bolting hardware: Fixe (Spain) makes 304 specifically for the USA, Lappas, Bonier, Sport Bolting, Climbing Taiwan, GIPFEL, Vertical Evolution, Mad Rock, any missing?

I (Bolt Products) initially started with 304 but very soon offered all our range in both 304 and 316. The demand for 304 gradually dropped and changes in the cost of the material eventually made the difference between the two materials fairly small, it amounted to around 5% of the finished product retail price. Added to the increasing hassle of maintaining two stock ranges and minimal demand I dropped 304 altogether about ten years ago.

However I keep both on my website so see if demand has changed, if it did I would start 304 again but so far this year only two customers have asked for it and both were quite happy to take 316 instead (and pay for it).

Locally we have some 304 stainless bolts over sixty years old still doing their job nicely here in Germany.

The ASCA orders Fixe hangers (with custom "ASCA" stamp) specifically in 304, since the stainless mechanical bolts we use (Power-Bolts) are only made in 304, so it'd be kinda silly to have 316 hangers (and with a minimum order size of 6,000 hangers for the ASCA stamp, cost would certainly add up). All the stainless steel glue-ins we supply are 316, but I honestly don't know if you can even buy a 304 glue in anymore? Any bolt replacement near the ocean is all titanium.

I both agree and disagree with this argument. It depends upon the hat I'm wearing at the time.

As an individual, I'm swayed by the "show me the bodies" argument - ie, if I see lots of traffic and yet, I have no need to step over bodies at the base of the climb, then I'm all good. Let's go!

Let's imagine that at well as failed bolts, we reported bolts that didn't fail. What would social media look like? The elephant in the room for all these discussions is the tens of thousands of 304 bolts doing sterling service right around the world.

Now let's change hats. Let's adopt the hat of a professional engineer, or route maintainer or bolt manufacturer. And yes, even a distributor IMO should be wearing that hat. My concern is not that a bolt might fail while I'm on it, it is the much more vexing concern that others may rely on my judgement to assess their personal risk. This is a very different matter, and to apply the "I see no bodies" test is unconscionable.

Consider three points -

a) In many environments, the two grades, 304 and 306, are equivalent in all important respects.

b) But there are environments where experience says 316 is superior.

c) I know of no situations where 304 is superior.

 Now factor in the cost differential..... it is definitely diminishing toward zero.

To tackle this one, we don't need the prescriptive "HowNot2" so much as a new show entitled "Why Wouldn't U".

Think how often "Why Wouldn't U" underpins the actions driven by experience. Stopper knots for one.

Maybe we are arguing about the wrong things?

Too funny, almost all stainless steel sleeve bolts being placed in the US are 304, why would you bother pairing it with a 316 hanger.

DrRockso RRG wrote:

Too funny, almost all stainless steel sleeve bolts being placed in the US are 304, why would you bother pairing it with a 316 hanger.

It's one of those US things, in Europe you'd really struggle to buy a 304 bolt, the building codes make 316 the do-it-all fastener and nobody trusts the site guys to know the difference.

Jim Titt wrote:

It's one of those US things, in Europe you'd really struggle to buy a 304 bolt, the building codes make 316 the do-it-all fastener and nobody trusts the site guys to know the difference.

You all use Stainless Sleeve bolts in Europe? I've scarcely seen one.

Sleeve bolts? They exist but nobody uses them for climbing.

Well since we have learned that much of what has been sold as 316 is actually 304, i am pretty sure the UIAA has really made a pointless regulation. Unless there is continuous testing by an independant climbing organisation, it all means nothing. With 36 years of personal experience placing 304 in my region, I feel no guilt continuing to do that. There is still plenty of carbon steel junk around for me to focus on.

timothy fisher wrote:

Well since we have learned that much of what has been sold as 316 is actually 304, i am pretty sure the UIAA has really made a pointless regulation. Unless there is continuous testing by an independant climbing organisation, it all means nothing. With 36 years of personal experience placing 304 in my region, I feel no guilt continuing to do that. There is still plenty of carbon steel junk around for me to focus on.

This ^^^. There is a recent MP thread concerning stresses/cracking introduced during the creation of threads in stainless steel, apparently unrelated to corrosion. Jim Titt commented on how different batches of SS bar stock, intended to be made into bolts, were not at all consistent. The climbing community has neither will nor funds for continuous testing by an independent climbing organization. The result being that we use hardware store-quality bolts and make do as best we can. This does not sound optimal but has actually served us well for decades.

Current best practices might be:

Dry locations inland = any stainless steel; 

For locations at or anywhere near the coast = titanium. 

For 2-bolt top anchor = aim to use two bolts sourced from different batches/retailers/manufacturers.

David Reeve wrote:

I both agree and disagree with this argument. It depends upon the hat I'm wearing at the time.

As an individual, I'm swayed by the "show me the bodies" argument - ie, if I see lots of traffic and yet, I have no need to step over bodies at the base of the climb, then I'm all good. Let's go!

Let's imagine that at well as failed bolts, we reported bolts that didn't fail. What would social media look like? The elephant in the room for all these discussions is the tens of thousands of 304 bolts doing sterling service right around the world.

Now let's change hats. Let's adopt the hat of a professional engineer, or route maintainer or bolt manufacturer. And yes, even a distributor IMO should be wearing that hat. My concern is not that a bolt might fail while I'm on it, it is the much more vexing concern that others may rely on my judgement to assess their personal risk. This is a very different matter, and to apply the "I see no bodies" test is unconscionable.

Consider three points -

a) In many environments, the two grades, 304 and 306, are equivalent in all important respects.

b) But there are environments where experience says 316 is superior.

c) I know of no situations where 304 is superior.

 Now factor in the cost differential..... it is definitely diminishing toward zero.

To tackle this one, we don't need the prescriptive "HowNot2" so much as a new show entitled "Why Wouldn't U".

Think how often "Why Wouldn't U" underpins the actions driven by experience. Stopper knots for one.

Maybe we are arguing about the wrong things?

when it's replacing one of thousands of plated bolts in less than stellar environments... (yes, i do realize you're making a comparison to 316 ;-)

Steve Bartlett wrote:

This ^^^. There is a recent MP thread concerning stresses/cracking introduced during the creation of threads in stainless steel, apparently unrelated to corrosion. Jim Titt commented on how different batches of SS bar stock, intended to be made into bolts, were not at all consistent. The climbing community has neither will nor funds for continuous testing by an independent climbing organization. The result being that we use hardware store-quality bolts and make do as best we can. This does not sound optimal but has actually served us well for decades.

Current best practices might be:

Dry locations inland = any stainless steel; 

For locations at or anywhere near the coast = titanium. 

For 2-bolt top anchor = aim to use two bolts sourced from different batches/retailers/manufacturers.

Sound!

Brilliant to recommend anchors are paired from different batches/retailers/manufacturers. 

Next level up is simply 100% TI mechanical anchors …Zero modeled material degradation over time 

Funny, the trajectory of this discussion. My intention was to see if Americans gave the same weight as European, Canadian, and Australian, etc counterparts about the EN/UIAA rock anchor standards, and the replies give credence to a much larger issue at hand: cost and accessibility. (The same issues that also plague other countries.)

In the USA, I’d definitely say there is a “price premium” given to 316 over 304. 

Example:

#1 - USA quote for stainless steel laser-cut & tumbled bolt 304 vs 316 = 109%

#2 - Strong Bolt 304 vs 316 = 71%

#3 - Power Stud 304 vs 316 = 31%

#4 - Red Head 304 vs 316 = 53%

ChatGPT answer: “In the U.S., 316 stainless steel generally costs about 50–70% more than 304, with approximately 60% being a reasonable average estimate.” 

Hangers are sorta a different story, as most hangers are all imported. 

Fixe Hardware: 304 $3.06, 316 $3.40 = 11%

Sport Bolting: 304 $3.50, 316 $3.80 = 9%

Lappas: SUL 304 vs 316L:  22%

CTW 304 vs 316L = 11%

Just some data for comparison, based off quotes we get from manufacturers for 304 vs 316 hardware:

Quicklinks: 10%

SS Carabiners: 10%

Wedge Bolts: 18%

Taiwan quote for stainless steel laser-cut & tumbled laser-cut bolt 304 vs 316 = 25%

316SS is noticeably more expensive in the States; it’s also quite difficult to track down any imperial-sized sleeve bolts made of 316SS.

So to expand the particularly 316SS selection, metric-sized fasteners have to be imported, as well as metric drill bits. I find there's a lot more 316SS options outside the USA. 

With glue-ins, the case is sorta different, provided materials can be imported. And whether they're made domestically or abroad, I doubt rock climbing bolt manufacturers are adding an arbitrary 316 price premium to their retail. Therefore making glue-ins the more affordable/accessible domestic option for 316SS. 

So to Dave Reeve or (Australia), Jim Titt (Germany/EU), and us (Taiwan/Asia), I think we're working with a quite different platter of offerings & resources over here. But with global supply chains expanding and the interchange of information, it's overall getting better and moving towards sustainability.

The States are still battling a plated-carbon steel hardware endemic to boot. 

The hassle is price instability, you can get a quote today but in six months things can look completely different. Stainless prices to the importer (and on the the customer) are based on on the world price of steel and then the alloying surcharge which is the price of the nickel, chromium, molybdenum and anything else. Nickel is the worst for fluctuation percentage wise followed by chromium and since I've been in business nickel has fluctuated between around $7,000 per ton to over $100,000 per ton (and that inside of three years) where in fact thr metals exchanges were closed and it stabilised at around $50,000 for  a period. At the moment it's around $16,000 and it makes up around 13% by weight of 316. 

All this (and stuff like Covid, blocking the Suez canal  and insane wars started by meglomaniacs) means the price and maintaining a stable pricing structure is a real struggle. The US stock price for 316 is currently insane, smashing 50% tariffs on the producing countries isn't helping.

OP, you make some good points. A campaign to replace all the 304 in the Southwest with 316 would amount to a huge waste of time and a lot of unnecessary damage to rock. Hopefully, after pulling a handful of decades-old, rust-free bolts, the well-intentioned would move on to something useful like volunteering at food banks.

As for developers, most of us will change our behavior if we see rust on old bolts. Shiny, 30+ year-old 304 bolts impress us a lot more than a warning on a box (or an online scolding from some humid coastline). The Prop 65 analogy is apt. If anyone took such warnings seriously, they'd be utterly paralyzed.

Climbing Taiwan wrote:

Funny, the trajectory of this discussion. My intention was to see if Americans gave the same weight as European, Canadian, and Australian, etc counterparts about the EN/UIAA rock anchor standards, and the replies give credence to a much larger issue at hand: cost and accessibility. (The same issues that also plague other countries.)

I'd be surprised if there was more than a handful of independent developers in the USA that paid much attention to what the EN/UIAA rock anchor standards said

Mark O'Neal wrote:

I'd be surprised if there was more than a handful of independent developers in the USA that paid much attention to what the EN/UIAA rock anchor standards said

I know I for one couldn't care less about their "standard". 

Climbing Taiwan wrote:

It's well-known 304 stainless steel has been popping up as the primary culprit of anchor/bolt failures in corrosive environments. And now with the latest chemical analysis of the sample on Kalymnos, a circumstantial 316SS.

I'm not sure if you were trying to suggest 316 steel is suspect now too but it came across that way.

To clarify for other readers, David's article states that the problem for those 316SS bolts that broke was in the category of manufacturing defect and not environmental (even though they were located in Kalymnos). Quote the linked article's conclusion:

"Until proven otherwise, all installed 10mm Petzl Goujon expansion bolts of vintage, say 2000 to 2005, should be treated as dangerous. It should be emphasized that this condition arises from the nature of the bolt itself, and is independent of its installed environment."

My definition of an expert is someone with a solid understanding of the limits of their knowledge. As an expert, one's role is to reveal the unknown-unknowns so they become known-unknowns. By such endeavors we reduce the chances of getting whacked by something coming out of left field.

Sulphate status is, for most crags, a known-unknown. We know that sulphate crags eat 304, but we don't know if it is present. On the best evidence available, this risk can be mitigated by substituting 316 for 304. However, firstly we hit the cost barrier as discussed upthread, and secondly there is yet another known-unknown to manage. Almost certainly, most 316 you purchase will be out of specification.

Subsequent to the fatal accident on Kalymnos, we should now be warned of the hazard of making glib generalisations like 316 good, 304 bad. The bolts that failed there were the first true 316 I have ever encountered, and if there had been a risk of SRB-attack, I believe these bolts would have mitigated it. But then an unknown-unknown came sailing in out of left field with fatal consequences. I'm confident we can tame this one with a bit more investigation but note that it will become an additional known-unknown. Whilst it might be comforting to mutter "bad production batch" and swiftly move on, such a response is delusional. If you have never done so, take a look at the process involved in certifying a stainless steel bolt under a safety critical regime. This level of QC will never be available for climbing bolts and thus how can we ever be sure that whatever caused the last "bad batch" couldn't happen again?