SCC, 316ss, and what's going on in Taiwan


Original Post
Nate Ball · · Portland, OR · Joined Aug 2010 · Points: 8,480

Howdy folks. I wanted to reach out to glean perspective from the community on a rather niche topic: stress corrosion cracking of stainless steel hardware at seaside crags. I have been in touch with Alan Jarvis, Tomas Prosek, Martin Roberts, and others, and think I have a fairly well-founded understanding of the situation. I want to provide a little context, so that the questions I'm asking are a little more clear.

Taiwan's premier climbing area is the Dragon Cave, a seaside crag of quartz conglomerate. There have been bolt failures from SCC dating back to the mid 00's, starting with mechanical bolts (mostly Petzl Long Life) and more recently including Ferno, Fixe, Austrialpin, and Petzl Collinox glue-in bolts. All of these are believed to have been 304ss. In 2005-2007 and 2011-2013 there were large-scale efforts to replace all mechanical bolts with 316ss glue-ins. In 2014, I raised concerns that these would also be subject to SCC. The locals have slowly transitioned towards titanium, electing to produce their own cast Gr5 Ti bolts rather than continue to buy from Titan Climbing for "personal" reasons. At the same time, an internationally-traveled Singaporean guide has been replacing many 304ss bolts with Titan Climbing bolts. The agreement seems to be that Titan Climbing U-bolts be used for anchors, and the Taiwan-made Ti bolts for lead bolts. A lot of Eterna's have also been placed as lead bolts, as the rate of installation has been too slow for the guide and many climbers who support his effort.

Currently, most 304ss bolts have been replaced, but the local team is stalled on the idea of replacing 316ss with the Ti bolts they already have. The guide is currently out-of-country and is most likely going to avoid the drama of continuing to rub against the nationalistic grain. There is not yet any precedence for failure of 316ss in this environment, but the knowledge is that it will happen eventually. The oldest are from 2005, and at a specific crag where there have been SCC failures previously. There are several hundred others in the same age range spread throughout the vicinity. The local team does have a HydraJaws pull-testing machine which was used mostly to test 304ss, but this has been abandoned as all 304ss are being replaced regardless of test results. Very few 316ss bolts have been tested, but all have passed, and there has been no systematic testing in many months.

My question to this community is "What would you do?" Tied up with this are the following questions: Do you think 316ss should remain until there is a precedence for failure? How would you go about testing them? Would you even bother? At what point would you make the determination that bolts should be replaced? Would you do it by individual crag, or route, or bolt? Which material or bolt type would you prefer to use? Do you have concerns about the longevity of either type of titanium bolt? And why?

I would be happy to provide any further clarifying info. Thanks for any and all response.

Jim Titt · · Germany · Joined Nov 2009 · Points: 490

John will be along to tell you to bolt it all in titanium in a moment, I´ll tell you to wait and see what happens with the 316 and/or wait until later this year when we should be bringing out a new range of 1.4462 bolts at a reasonable price. But my advice is you can´t tell climbers anything and I´d just keep well out of the whole affair and let the people doing the work and paying the bills decide.

Nate Ball · · Portland, OR · Joined Aug 2010 · Points: 8,480

The ones paying the bills are the community at large, not the group actually doing the work. The "foreign" guide has paid for what he's done mostly on his own, with a little help from supporters. The local group has 900+ Gr5 Ti bolts, and the general consensus is to use titanium for all future rebolting. The question isn't so much what to use as how it should be done. Thanks for your input, and I eagerly await that box o' bolts.   

Charlie S · · Ogden, UT · Joined Aug 2007 · Points: 1,471

My understanding of stress corrosion cracking requires that the component be under constant load.  You shouldn't have that with a glue in.

However, regular corrosion in salty environments or humidity; different story.

Nate Ball · · Portland, OR · Joined Aug 2010 · Points: 8,480

Internal stress from manufacturing process, even in hot forged bolts (eg: Petzl Collinox), has shown to be enough to cause failures in less than 10 years.

Daniele Nicolodi · · Boulder, Co · Joined Nov 2016 · Points: 5

Hi Nate,

internal corrosion in marine environment is a serious issue in Italy and France as well. I'm far from being an expert on the matter, but I have read a bit on the argument and my understanding is that 316ss is considered way safer than 304ss but there are not yet enough data to be sure about it. Another problem is that stainless steel classifications are very wide and not all 316ss are the same, let alone the issue of tracing the certifications of the materials used in the manufacturing process. Namely identical bolts from the same manufacturers but from different batches show different characteristics.

Maurizio Oviglia is the person that in Italy monitors the issue and is pushing for action and has contacts with whom in the French Alpine Club is doing the same in France. I'm sure he would be happy to learn more about the situation in Thailand and tell you more the conclusions that have been reached with the tests in Europe. You may get in contact with him, you find him on Facebook or I can give you his email address.

Cheers,
Daniele

20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,352

To answer the OP's question, there is absolutely no benefit in waiting to replace the bolts. Eventually the bolts will suffer from SCC and require replacement, or require replacements for other corrosion related issues. It's not a question of if, just when. By contrast, titanium bolts have no known specific lifespan in any climbing environment, and thus you dont have to worry about replacing them ever (at least not in your lifetime). As such, I would view the scenario as wait until something breaks and someone gets hurt and then replace everything with titanium, or replace everything now and prevent that scenario from occurring in the first place. Seems like an easy choice to me. Why wait to replace something that will eventually need replacing anyway? You're taking a chance for absolutely no benefit other than to put off the work. Titanium bolts last basically forever in practical terms. Waiting five years to place them wont extend their lifespan if that's what you're thinking.

I would recommend using titanium--I wouldent bother messing around with 2205 duplex stainless. Those bolts have been tested in Thainland by Martin Roberts and found to show visible corrosion after less than a year and a half. Ultimately no one really knows how long any duplex stainless steel will last in climbing so you're taking a chance with any stainless steel alloy. The only stainless steel possibly worth considering would be 254SMO which has not shown any corrosion after 2 years in Thainland, but it's so expensive it's pointless. Select titanium and know you'll never have to worry about it again.

Here is a photo of one of the 2205 bolts in the Thailand UIAA testing group:


Here are two of many photos I have of 316 glue-in bolts:



Nate Ball · · Portland, OR · Joined Aug 2010 · Points: 8,480

Correction: the Petzl Collinox bolts that failed simultaneously were tested and shown to be 304ss. The climber was top-roping and not far from the ground, so thankfully it ended in only a bruised butt.

Also, titanium has been decided on as the only option. I'm sure any future production of bolts will be done in-country.

Mike Slavens · · Houston, TX · Joined Jan 2009 · Points: 35

Has the UIAA released any sort of final results and/or report of their Thailand corrosion testing?  I've seen a few updates and the odd picture here and there but nothing all encompassing.

Jim Titt · · Germany · Joined Nov 2009 · Points: 490
Mike Slavens wrote:

Has the UIAA released any sort of final results and/or report of their Thailand corrosion testing?  I've seen a few updates and the odd picture here and there but nothing all encompassing.

No, none of the bolts have failed so it´s a work in progress. As far as I know (I have bolts in the test program and am on the working group) there´s no defined protocol about what is going to be tested, how or when. 

Jim Titt · · Germany · Joined Nov 2009 · Points: 490
20 kN wrote:


I would recommend using titanium--I wouldent bother messing around with 2205 duplex stainless. Those bolts have been tested in Thainland by Martin Roberts and found to show visible corrosion after less than a year and a half. Ultimately no one really knows how long any duplex stainless steel will last in climbing so you're taking a chance with any stainless steel alloy. The only stainless steel possibly worth considering would be 254SMO which has not shown any corrosion after 2 years in Thainland, but it's so expensive it's pointless. Select titanium and know you'll never have to worry about it again.

Here is a photo of one of the 2205 bolts in the Thailand UIAA testing group:


Here are two of many photos I have of 316 glue-in bolts:



I am awaiting more detail on the 2205 bolt pictured as the "corrosion" appears to be actually a glue smear. 

The other two bolts are 304 (or worse) as Raumer have only very recently changed to 316 after producing a large number of sub-standard bolts which had to be replaced (they changed in late 2013/2014). The eye shape of the 316 anchors is different.and they are stamped 316L.

John Byrnes · · Fort Collins, CO · Joined Dec 2007 · Points: 451

Hi Nate,

Over the years you and I have exchanged a lot of email on this issue, so you know where I  (and 20kN obviously) stand and I don't need to repeat it.   

However, I didn't know (or forgot) the Taiwan locals were using Grade 5 Ti.   It will be interesting to see if the service life will be less/same/more than Grade 2.   

FWIW, a number of years ago Mike S, the metallurgist who worked on the original Tortuga design, proposed making investment casted glue-ins from Grade 5; a process he uses every day in his aerospace job.  He and Angele went back and forth on the pros and cons, but both eventually agreed that the lower cost and better manufacturability would come at the price of less corrosion resistance, compared to Grade 2.

John Byrnes · · Fort Collins, CO · Joined Dec 2007 · Points: 451
Daniele Nicolodi wrote:

Another problem is that stainless steel classifications are very wide and not all 316ss are the same, let alone the issue of tracing the certifications of the materials used in the manufacturing process. Namely identical bolts from the same manufacturers but from different batches show different characteristics.

It might not be variablility in the manufacturing process, but more likely, variability of the micro-environment that each individual bolt is placed in.   I have seen many routes where identical bolts on the same route have wildly varying degrees of SCC.   Usually, the lower the bolt, the faster it cracks due to receiving more rain runoff than bolts higher up.  It's the rain runoff (or sea spray) that carries the ions that start SCC, and the more rock it runs down, the more ions are picked up and deposited on the bolts.  Obviously, of bolts that receive direct sea spray, the lower ones receive more.

Ryan Bowen · · Bend, Or · Joined Mar 2017 · Points: 85
Nate Ball wrote:

Internal stress from manufacturing process, even in hot forged bolts (eg: Petzl Collinox), has shown to be enough to cause failures in less than 10 years.

The bolts aren't stress relieved after forging?  Seems a bit dicey. 

20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,352
John Byrnes wrote:

Hi Nate,

Over the years you and I have exchanged a lot of email on this issue, so you know where I  (and 20kN obviously) stand and I don't need to repeat it.   

However, I didn't know (or forgot) the Taiwan locals were using Grade 5 Ti.   It will be interesting to see if the service life will be less/same/more than Grade 2.   

FWIW, a number of years ago Mike S, the metallurgist who worked on the original Tortuga design, proposed making investment casted glue-ins from Grade 5; a process he uses every day in his aerospace job.  He and Angele went back and forth on the pros and cons, but both eventually agreed that the lower cost and better manufacturability would come at the price of less corrosion resistance, compared to Grade 2.

We've placed many grade five bolts from back before Titan Climbing existed and we were making our own material. So far they are holding up the same as all the grade two bolts. None of our Ti stuff shows any sign of corrosion of any type that is visible. 

Nate Ball · · Portland, OR · Joined Aug 2010 · Points: 8,480
Ryan Bowen wrote:

The bolts aren't stress relieved after forging?  Seems a bit dicey. 

Of course they are, but the residual stresses are still there, and clearly enough to facilitate SCC.

Nate Ball · · Portland, OR · Joined Aug 2010 · Points: 8,480

So perhaps I should be a bit more explicit in setting up my question. The situation seems to be that nothing at all is being done about the several hundred 316ss bolts at our crag. After a double-anchor failure in July 2015, one would think that we would be moving away from any material that could possibly create the same scenario. We're already had two severe injuries from bolt failure in the past, and several near-misses. Admittedly, these were all 304ss bolts, but my understanding is that 316ss shows all the characteristics of vulnerability and thus eventual failure.

So, how do you think the 316ss bolts should be tested? Or would you just skip that in favor of rebolting with titanium?

Ryan Bowen · · Bend, Or · Joined Mar 2017 · Points: 85
Nate Ball wrote:

Of course they are, but the residual stresses are still there, and clearly enough to facilitate SCC.

Interesting.  Learn something new every day.

I've never designed anything that had to be forged or in a marine environment, so my experience is apple to oranges. 

20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,352
Nate Ball wrote:

So perhaps I should be a bit more explicit in setting up my question. The situation seems to be that nothing at all is being done about the several hundred 316ss bolts at our crag. After a double-anchor failure in July 2015, one would think that we would be moving away from any material that could possibly create the same scenario. We're already had two severe injuries from bolt failure in the past, and several near-misses. Admittedly, these were all 304ss bolts, but my understanding is that 316ss shows all the characteristics of vulnerability and thus eventual failure.

So, how do you think the 316ss bolts should be tested? Or would you just skip that in favor of rebolting with titanium?

Skip the testing. What is the point? In the amount of effort you would exaust hauling up a hydraulic testing machine, putting it in place, testing each bolt, moving it over to the next route, repeat, repeat, you could just rebolt the thing and be done with it. Even if you do test them and they pass, then what? What about six months later? And another six after that? Are you going to keep testing them over and over? That's way more work than just replacing them.

I'd put this on the shoulders of the community developers and tell them they all have a combined responsibility in replacing this stuff quickly. If no one wants to step up and do it, then start chopping bolts with an angle grinder until people step up. Removing unsafe bolts and not replacing them is far better than just leaving them there until someone gets killed.

Also, if you want to do a quick test to see if a bolt has been drastically reduced in strength by SCC, get a really solid hammer (like 4 lbs), and a funkness cable and funkness the glue-in straight out hard. That should produce at least 6kN on a hard swing. Just be sure to pull straight out so you dont bend the bolt and damage it (not that it matters much as they all need to be replaced anyway). This wont guarantee the bolt is not suffering from SCC, but it will guarantee it has not degraded to such a point that it will break easily. The downside is funknessing really hard with a big hammer is pretty damn hard on your arm and 700 bolts of that crap is going to suck hugely. I’d just replace all the stuff or chop it if no one wants to step up and do what needs to be done.

Mike Slavens · · Houston, TX · Joined Jan 2009 · Points: 35
Jim Titt wrote:

No, none of the bolts have failed so it´s a work in progress. As far as I know (I have bolts in the test program and am on the working group) there´s no defined protocol about what is going to be tested, how or when. 

Is there a planned end date?  Or date for an interim report?  Is the current data (bolt types, testing to-date) available anywhere?

I know they want to keep the bolt locations a secret for obvious reasons, but just wondering if there is anything the working group can share. 

Jim Titt · · Germany · Joined Nov 2009 · Points: 490
Mike Slavens wrote:

Is there a planned end date?  Or date for an interim report?  Is the current data (bolt types, testing to-date) available anywhere?

I know they want to keep the bolt locations a secret for obvious reasons, but just wondering if there is anything the working group can share. 

No idea about anything, it´s being run by the UIAA so anything might happen, sometime in the distant future. Whether I live long enough to see tangible results is debatable.

Guideline #1: Don't be a jerk.

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