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Metallurgical Study on Stainless Steel Climbing Bolts
A Boulder, Colorado metallurgist and climber, Angele Sjong, was given a bolt hanger that had been removed from the cliffs of Railay Bay after several years of use. This particular bolt had been removed by a climber simply by bending it with their hand.

Sjong approached her employer and requested to perform an in-depth study of the steel hanger in an attempt to determine the causes of the accelerated corrosion and how it relates to the Southern Thailand environment. Sjong subjected the sample to a battery of chemical tests and extensive scrutiny under serval high-powered microscopes. The results were published in a metallurgical journal.

Sjong's study provided the climbers of Thailand with several much-needed answers. The quick and easy solution being: Stop using steel!.

End of Stainless Steel Climbing Bolts

As a bunch of uneducated (from a Yale-educated metallurgical stand point) climbers, we felt like this was an obvious solution, but we felt like we needed to know why the steel was corroding before committing to a replacement alloy. We entertained a wide variety of theories, like: salty air, humidity, naturally occurring compounds inside the rock. We were pleased to find that ultimately it proved to be a convergence of all these factors.
We had every indicator going the wrong way... We were screwed. - Mark Williams, Ph.D.

Recipe for Corrosion

It comes as no surprise that the whole process starts with rain. A lot of rain.

Southern Thailand is located in the Tropics, which basically has two seasons: wet and dry. During the wet season Thailand sees a biblical amount of rain. When the rain hits the top of the cliffs, it weathers these large, bathtub-like holes. The water collects begins to seep into the naturally porous limestone. This same water absorbs additional minerals as it seeps through the limestone, resulting in a different chemical composition by the time it makes contact with the bolts embedded into the rock.

Compounding the rain issue is the vegetation that forms atop the cliffs and feeds on collected rain water inside these same bathtub-like pools. The plant growth increases the acidity of the water as CO2 is forced out the root system, allowing the water to erode expanding paths through the inside of the rocks. Many of these paths are just big enough to allow water to flow, while others are so large that they could easily accommodate an adult human. Due of the mushroom shape of these rock formations, which give climbers the coveted overhanging rock faces to climb, the internal flow paths have an easier time reaching the surface, and ultimately, the bolts.

Stress Corrosion Cracking

One of the most interesting things discoveries resulting from Sjong's chemical analysis was presences of abnormally high amounts of magnesium.

While the source of the magnesium is still a topic of debate and requires further study, it is generally accepted that it occurs naturally within Thailand's rock. Though unproven, perhaps the most popular theory is that water traveling through these paths acquires the surplus magnesium made available as the rock itself dissolves. The best evidence for this argument comes from simply looking at the rock face. With so much of the rocks' scenic beauty owed to the thousands of stalactites hanging from the rock walls, it's not hard to see how the same processes that created those stalactites are also deteriorating climbing bolts.

Magnum doesn’t actually corrode steel. Magnum sits on the bolts and absorbs the chloride in the sodium chloride (salt) that is in the air from the close proximity to the water. Traditionally, the chloride is the primary culprit when it comes to corroding steel bolts. The addition of a protective layer of chromium into the alloy is what makes traditional steel into stainless steel. Chloride is capable of eating through this chromium layer and working into the now-unprotected traditional steel, which leads to very serious and very specific type of corrosion called Stress Corrosion Cracking (SCC).

What makes SCC a very significant part of our struggle is the lack of exterior rust in afflicted bolts. This denies Thailand climbers a visual cue to help determine the integrity of a given bolt. Often times, bolts which look flawless on the surface, hide a surprise layer of internal corrosion, making for a potentially deadly situation.

Furthermore, the lack of consistency with respect to predicting failure-prone bolts has proved confusing at best. Perhaps a bolt is close to a water source, fixed to wet rock or covered in salt. Yet this bolt will experience no issues and function as expected. While on some routes with no overt warning signs, bolts only meters apart will demonstrate entirely different responses to stress.

Again, we approached our metallurgist friends with this issue and they offered a solution: It comes down to the micro-climate surrounding the bolt. Ultimately, as we cannot understand the climate around each bolt individually, we were left with no other option but to find a new alloy capable of resisting corrosion under most potential micro-climate scenarios.

Finding a New Alloy

Titanium seemed the obvious choice after the Cayman Island Crew's consultation with metallurgists and subsequent success. As Jim Bowes' Ushba was the only climbing equipment manufacturer working with titanium, they were approached to design a suitable glue-in bolt. Upon completion, Ushba branded the new design the "Tortuga"-- the original name given to the Cayman Islands by the Spanish.

The Cayman Islands Crew placed their first new titanium bolts in 1998. After two years in the rocks, no signs of corrosion were evident. It appeared as though the metallurgists had been correct and this could be a potential solution for the issues facing Thailand's cliffs.

In 2000 those same titanium bolts made their way to Thailand. After more than a decade since first used in Thailand, these initial titanium bolts still shine like the day they were placed.

The Glue Matters, Too

Alongside our experimentation with the different kinds of stainless steel, there was concurrent testing done on different adhesives and epoxies that were commercially available at the time. By the late-nineties it was obvious to all that any type of glue-in bolt was extending the life of bolts. Understandably, the logic was that the glue formed a protective layer between the rock and the metal. We tried several compounds but found the majority of them were not water resistant enough for Thailand's cliffs. In 2004 Hilti debuted a glue called "RE-500". What set RE-500 apart was its primary use: Glueing things underwater. Once cured, RE-500 is completely waterproof, making it the glue of choice even today.
The RE-500 with a titanium bolt seems to be the magic combination. - Tom Cecil, Guide & Thaitanium Member



2 Comments

    jorge

    On:June 28, 2012

    good afternoon, i would like to make my final project about your bolts. it is very interesting! i am not climber but i like so much of sport in general. congratulation!

    Rances

    On:September 28, 2012

    I am wondering where can the titanium bolts be purchased?


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History of Thailand climbing


Who popularized rock climbing in Thailand? James Bond or a postcard?
May 1, 2012 | 0 comments

While no one knows for sure when the first climbing in Thailand began, recent history begins in the 1980s when Pra-Nang Bay in Southern Thailand was known only to a few adventurous travelers, and as a relatively unexplored beach destination at that. Few dared to venture outside the safety and comfort of Phuket Island’s giant beach resorts. But seeking new adventures, travelers eventually made their way across the bay to Phi Phi Islands and a small fishing town by the name of Krabi.

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Equally unclear as Thailand climbing's origins is who should be credited with realizing the potential for rock climbing in the Pra-Nang Bay. A few tales have been passed around about the discovery of these fabled cliffs. In one version it was tourists traveling to the Phi Phi Islands Read more

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