Should Stainless Steel bolts become a thing of the past?

Posted by Sarah Stirling on 16/06/2014
Titanium bolts - the way forward? Photo: www.titanclimbing.com

Sheffield’s Titanium bolt guru, Martin Roberts, thinks Stainless Steel bolts should become a thing of the past; not just in super corrosive tropical environments like Thailand, but also in the UK. Sarah Stirling finds out more.

When Martin decided to develop new sport climbing routes in Thailand a few years ago, he ran into a problem: Thailand’s environment is so corrosive the bolts had to be Titanium, but this light, strong and corrosive-resistant metal was incredibly expensive compared to traditional Stainless Steel.
 
Undeterred, Martin read a lot of books about manufacturing, spoke to a range of experts, designed a lot of bolts, out-sourced production to China and, finally, set up his own thriving business manufacturing Titanium bolts in Sheffield last year.

Aren’t Titanium bolts mostly useful in tropical coastal climbing areas, because these conditions accelerate corrosion?

It’s true that conditions are particularly bad in tropical coastal environments. Some routes in Thailand have been re-bolted with Stainless Steel five times in 20 years because the bolts have corroded so quickly. Climbers have occasionally broken both belay bolts at the same time in Thailand with just their body weight. Stainless Steel bolts don’t only fail on limestone in tropical coastal areas though. They have catastrophically failed in Basalt on Hawaii, in sandstone in South Africa 80km from the sea, and on Cuban crags more than 25km inland, amongst many other places.

OK Titanium is lighter, stronger and more corrosion resistant than Stainless Steel. But surely Stainless bolts work fine in the UK’s benign environment. Why do you recommend using Titanium bolts here?

I don’t think Stainless Steel is the best material for bolts. It certainly has a very limited lifespan compared to Titanium, and Titanium bolts are now no longer ridiculously expensive, so it makes sense to use them instead. The Titanium I use is not stronger than Stainless Steel by the way: I use it because of its superior corrosion resistance. Good quality Stainless Steel bolts (316 or A4) should be fine for inland use but for coastal environments, I would recommend Titanium.

But isn’t our rock and environment pretty benign in terms of causing corrosion?

In very general terms, corrosion happens faster in hotter climates. However, the corrosion of metals is an extremely complex process, affected by many different factors including proximity to the sea, porosity, composition and dampness of the rock, ambient temperature, humidity, rainwater run off, and rotting vegetation within and on top of the crag. I think Titanium bolts would be particularly useful in UK coastal areas because of the salt spray environment.

Why is Thailand’s climate particularly corrosive?

Thailand has all the corrosive characteristics: proximity to the sea, karst limestone, and rotten vegetation on top of the crag, which rots and seeps through the sometimes-porous rock. There’s also acid rain, which dissolves the limestone and deposits all sorts of nasty compounds on the bolts, such as magnesium chloride and calcium chloride. The high ambient temperature is also a problem, and there’s high humidity and also low humidity to contend with, so the damp compounds are concentrated when the water evaporates. There are also lots of people climbing there and therefore lots of falls on the bolts.

How did you go about designing your own Titanium bolts? 

I asked the designers of the original Ushba bolt if they minded me putting their bolt back in to production. The Ushba bolt had been unavailable for about 10 years because the company that produced them was bought out, then the price of bolts doubled so sales plummeted.

Why the Ushba bolt?

It was a simple proven design and, up until then, the only Titanium bolt used for climbing. Back then I didn’t have the time or resources to produce a new design and we were desperately in need of a bolt to cure the increasingly dangerous situation. The Ushba designers were happy for me to start producing the bolt again.

How did you go about getting your bolt designs manufactured?

I made some minor improvements to the Ushba design and emailed drawings to a few companies specialising in the manufacture of small Titanium parts. One of the companies that produced samples for me immediately became my preferred supplier. Mechanical testing carried out in Sheffield confirmed that, not only did their bolts look great, they were manufactured to very tight tolerances - ie the finished bolts were extremely similar, which indicated very good consistency in their manufacturing methods.

Did you start selling your bolts straight away?

No, in those days I had the bolts made on a non-profit basis for myself and my friends. We set about bolting new routes and re-bolting existing routes with them: mostly in Thailand, Hawaii, the Cayman Islands and also a few crags in Brazil.

Did you have any previous experience or qualifications in manufacturing, or did you learn as you went along?

I’ve always loved repairing and manufacturing things but had not previously studied Titanium manufacture. I was fortunate to bump into the right people at the right time and glean a huge amount of knowledge from experts in metallurgy, machining, coatings, corrosion, mechanical testing, failure analysis, welding and more. I also spent a huge amount of time reading papers, online documents, and manufacturing literature.

You've done accelerated corrosion tests on your bolts, and said that there's no known case of a correctly placed Titanium bolt failing. What other tests have you had done on the bolts and do you have figures?

In those corrosion tests, a Stainless Steel hanger failed after less than 4.5 hours and the Titanium bolt was untouched after the full 30 days of the test. There is a huge amount of testing carried out on our products. The new Eterna bolts and U bolts we sell are certified to EN959 (the test all climbing bolts and anchors should pass - basically it’s to do with the dimensions and mechanical properties) and break at over 40kN - the minimum requirement is 25kN. A few other things we do: test every bar to make sure it's true to its material certificate, dye penetrant tests to inspect for cracks, 100% visual inspection at various stages, and potassium ferrocyanide tests for surface iron after passivation.

Titanium is harder to get hold of, harder to machine and more expensive. Do you think UK climbers are going to fork out for the more expensive Titanium when, as you said, Stainless Steel works fine in a lot of places?

Stainless Steels should last OK in inland areas but will last nowhere near as long as Titanium. It's not necessarily harder to machine but it is different and, yes, Titanium raw materials are more expensive than Steels. However, because we sell directly to customers and our overheads are lower than very large companies, we can sell our Titanium bolts cheaper than some Stainless Steel bolts. Even if you compare our Titanium bolts to the very cheapest steel bolts, Titanium will be the most economical option in the long run as they will last many times longer.

Can you tell me a bit more about the Thaitanium Project you’re involved with?

I've been supplying the Thaitanium Project with bolts for the last 4 or 5 years. It's http://thaitaniumproject.com/ a non-profit effort dedicated to providing and installing Titanium climbing bolts throughout the Railay peninsular in Thailand. This winter I placed 500 bolts in Thailand as part a long-term corrosion test in association with the UIAA (International Mountaineering and Climbing Federation). The goal is to compare the corrosion and failure rates of four different grades of Stainless Steel in five different designs and our Titanium bolts; some expansion bolts and some glued in with four different types of resin.

What made you decide to bring manufacturing back to Sheffield?

I’d been manufacturing Titanium bolts in China for four years, and wasn’t advertising anywhere, but people were somehow finding me and asking for bolts. It seemed there was easily enough demand to start my own production and get the bolts certified. Manufacturing in the UK would allow me to oversee every aspect of production. By that time I had already made a lot of contacts in the manufacturing, metallurgy, titanium stock-holding and mechanical testing industries in Sheffield and it seemed an obvious decision given the city's manufacturing heritage and it also being my home city.

How is that going - what pros and cons have you found to UK manufacturing?

Since starting the company in June 2013, we've gone from strength to strength: batches have got larger and sales faster. Dealing with China was always difficult with the distance, language and cultural differences. Now it’s easy and efficient. We drive a few minutes to purchase raw materials, tools and parts, or carry out mechanical testing. Die makers, passivation and welders with 30+ years experience with Titanium are also a short drive away. Almost everybody I’ve met through Sheffield manufacturing is a salt-of-the-earth type: honest, reliable and supremely helpful.

Any downsides?

The only downside is that labour intensive processes are costly here, so I've had to change designs to suit faster, more mechanised processes and make sure batches are large enough for the economy of scale to work in our favour.

So what's next for Titan Climbing?

We are currently developing two new Titanium lower-off designs that will have a comparable price to Stainless Steel and will, of course last an extremely long time, have no moving parts to seize up and be very easy and safe to use.

For more information, visit www.titanclimbing.com



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1) Anonymous User
17/06/2014
Stainless bolts in the UK are functional enough it seems to me and whilst I know little about it admittedly it seems odd that the only guy promoting this idea is the only guy selling them. Also wouldn't the design of them be harder to check to the untrained eye than bolt on hangars and in addition harder to place and easier to get wrong?
2) Anonymous User
17/06/2014
The DMM Eco anchor had tangs at the end of the two shafts. If the resin / metal bond failed, then the tangs had to be 'straightened out' for the anchor to be extracted - a bloody neat design feature. If the 40kN is from resin / metal bond failure in concrete then it is comparable with SS designs. Most data I have seen is in rock so has lower values, see http://www.cncc.org.uk/technical-group/downloads.php .

See http://british-caving.org.uk/wiki3/doku.php?id=equipment_techniques:meetings for November 2013 meeting and paper for cavers' views on Chloride Stress Corrosion Cracking.
3) Daniel Middleton(staff comment)
18/06/2014
There is a growing awareness that 316 Stainless Steels may not be the material of choice in some situations. The UIAA is funding in depth corrosion studies at the moment, with recommendations to follow as part of their Anchor Standard in due course. For more detail on bolts in general check out our guidance documents: https://www.thebmc.co.uk/bolts-guidance-documents
4) Anonymous User
20/06/2014
Be interesting to read the views of the stainless steel manufacturers, hard to believe the advertorial above tells the whole story.
5) Anonymous
01/07/2014
This comment broke the house rules and has been removed
6) Anonymous User
29/08/2018
Nice puff piece, with almost no actual data or understanding of materials science. Titanium has horrific response to chloride environments, which are those same ones that cause failure in AISI 304 type steels, and are attacked worse by organic acids - environments with lots of peaty water - than 316 steel.

While titanium alloys have higher stress corrosion cracking resistance than *some* corrosion resistant steels, they have worse fatigue life, fracture toughness and impact energies, mechanical properties that are fundamental to the functioning of a threaded fastener under load.

The cost delta between 6/4 titanium alloy - the type this man is most likely touting - and AISI 316 type steel is still huge, and the strengths at excellent corrosion resistance levels available in high performance corrosion resistant steels still eclipse titanium, and always will. These are fundamental materials properties.

Bumax, for example, have made a substantial career out of making very high strength fasteners - in excess of that achievable in 6/4 titanium with enviable corrosion resistance in coastal environments, and unit costs still below titanium alloys.

Titanium has some excellent merits, and applications in which it is king. However, high strength, fatigue resistant, corrosion resistant fasteners it loses out on one or more parameters to other fasteners.



But what do I know, I'm not a titanium screw salesman, I'm just a materials scientist with 15 years in aerospace.

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