“We had every indicator going the wrong way. We were your screwed.
Although we improved the life-span of some of the bolts with the glue-in style bolt and the higher grade steels, the corrosion persisted. At the same time as Thailand was dealing with this bolt problem, another group of climbers in the Cayman Islands were starting to see the same corrosion on their seaside cliffs. John Bryan and Skip Harper approached a metallurgist while back home in the United States with this problem and found that even from a metallurgical standpoint that this corrosion was very unique. One of the suggestions to John and Skip from the metallurgist was to change metals. They experimented with several different corrosion resistant metals and finally found one that had superior corrosion resistance to any steel, was very strong, fairly easy to find and was not outrageously expensive. This metal was Titanium. The new mission was to find some one willing to make these new Titanium bolts so the Cayman Crew could start placing them in cliffs and see what happened.
Back in Thailand there was also an effort to find a solution to this unique metallurgical problem. A metallurgist and climber Angele Sjong from Boulder, Colorado was given a bolt hanger that saw several years of use on the cliffs of Railay Bay that was broken off by someone bending it with their hand. Angele approached the company she was working for at the time to do an in-depth study of the hanger to try and an explain what was happening to the steel and why it would corrode so fast in the Southern Thailand environment. Angele was able to put the hanger under serval powerful microscopes, perform chemical testing and the results were published in a metallurgical journal.
The results from Angele's study did provide serval answers for us and a scientifically backed solution to the problem of using steel bolts in Thailand. The quick and easy solution being: Stop using steel! Now as a bunch of uneducated (from a 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 moving on to any replacement for the steel with any kind of confidence. We were pleased to find out that almost all our theories like the salty air, chemicals inside the rock and the heat and humidity were either dead on or at least close to what Angele's study told us. What we didn't realize is the combination of all of them would be the culprit.
It All Starts With RainThe whole process starts with rain. Southern Thailand is located in the Tropics, which basically has two seasons: wet and dry. During the wet season Thailand sees a huge amount of rain. When the rain hits the top of the cliffs, it weathers these larger, bathtub-like holes. The water collects and, with the naturally porous limestone, it starts to seep into the inside of the rock. The water picks up more minerals as it seeps through the limestone, giving it a different chemical composition by the time it hits the bolts in the rock.
Compounding that is the plant life that lives on the top of the cliffs and feeds off the collected rain water in these bathtub pools. The plants add more acidity to the water by respiring co2 through their roots, allowing the water to dissolve larger and larger paths through the inside of the rock. Some are just big enough for the water to squeeze through, and others can be so larger that you can walk inside of them. Because of the mushroom shape of these rock formations, which give climbers the overhanging rock faces to climb on, the internal flow paths have an easier time getting to the surface, the area where we place to the bolts. When you drill a hole to place a bolt you may be intercepting one of these internal flow paths. If that water that is already acidic from the rain and the co2 from the plants hits that bolt, that water could start the oxidation process and corrode the bolts.
Stress Corrosion CrackingOne of the most interesting things that Angele found in her chemical testing of the bolt hanger was the high amounts of magnesium. Where the magnesium came from is still up for debate and would need more study. But why the magnesium is important brings us to the next step in our corrosion process. The magnesium would most likely come from the rock. The popular theory, which would need more study to confirm, is that in the process of water moving through the internal flow paths, the water picks up magnesium by the desolation of the rock made possible by the acidic water. You can tell this is happening by just looking at the rock face. The formations that adds so much to scenic beauty of the place are the thousands of stalactites hanging from the rock walls. The process that forms those stalactites is the same process that allows corrosive elements to deteriorate the bolts. The acidic water flows through the rock and when it hits the surface and starts to flow out of the rock it forms the stalactites and stalagmites.
Magnesium doesn't actually corrode steel. Magnesium 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. The chloride is the main culprit that corrodes the steel bolts. The addition of a protective layer of chromium into the metal mixture or alloy is what makes steel into stainless steel. Chloride is able to eat through the chromium layer into the now unprotected normal steel to cause a very serious type of corrosion called stress corrosion cracking (SCC). What makes SCC very significant in our bolts is that you do not always see rust on the outside of the bolt. This presents climbers in Thailand with a difficult situation when choosing to clip or not to clip a bolt. Climbers may find the rusty bolt they do not want to clip is totally fine with the rust just on the surface and the perfectly shiny bolts may have SCC happening deep inside the bolt where a crack or cracks run all the way through the bolt and brake under body weight. This logically will lead to the unfortunate conclusion that there is no way to tell if the bolt is bad or not.
“You have consistent reprecipitation of magnesium.
No Way To TellWhat makes things more confusing is that we have not found any consistence in the bolts failing. Sometimes we see bolts in a spot where we would assume the bolts would be bad and they are fine. They may be close to the water, placed in wet rock and covered in salt and it will not brake after 10 to 15 years of being in the rock. We have found some routes that have bolts hold multiple falls and broke other bolts on the same route a few meters higher by hand. We approached our metallurgist friends with this problem and I think they came up with a logical explanation. What they said it comes down to is the micro climate around the bolt that will depict the rate of corrosion on the bolts. But because you will never be able to tell exactly what is happening to the bolt in that micro climate surrounding it, once it is in the rock it leaves us with only one thing to do, change metals.
The Cayman CrewNow lets go back to the Cayman Islands. After the Cayman Crew got the suggestion for metallurgists to try Titanium bolts they approached the climbing company Ushba run by Jim Bowes. The reason the Cayman Crew approached Jim is because Ushba was the only climbing company to make climbing equipment out of Titanium. They went through the process of designing a suitable glue in bolt and named it the Tortuga (after the original Spanish name of the Cayman Islands). The Cayman Crew started placing there new Titanium Bolts in 1998 and after two years in the rocks with no signs of corrosion it looked like the metallurgist were right and this could be the solution we were looking for. In 2000 Titanium bolts made there way to Thailand. Fast forward to present day and it has been a little more then a decade that these Titanium bolts have been in the rock and they still look like the first day they were placed. Now the exact reasons why Titanium works in the tropical Thailand environment is something I am still learning about at the time of this little write up. But as a humble climber this all comes down to two things, steel doesn't work and Titanium seems to be fine. As developers and re-bolters we will continue to observe and hope for the best.
“We thought that by isolating the steel for the chemicals in the rock (by using a glue) would help protect the bolts.
The Glue Matters, TooRight a long side the experimentation with the different kinds of stainless steel, there was also experimenting with the different glues or epoxies that were available to us. It was obvious by the late 90's that any type of glue-in bolt was extending the life of bolts. This was thought to be contributed to the fact that bolts were being protected from the internal water flow and the corrosive elements inside the hole by the glue. The first glue that was used was made by Hilti and was in glass capsules. Unfortunately this glue and a few others that were tried were not completely water proof and would eventually let the corrosion water seep through the glue to make concoct with the bolt. Thus again making the bolts susceptible to this unique type of corrosion and not solving the problem. Around 2004 Hilti put out a glue called RE-500. What made RE-500 so special was that it is made for glueing underwater and is waterproof once completely cured. Once we got wind of this new waterproof glue we jumped of the band wagon and that has been the glue of choose ever since.
“RE-500 and titanium bolts seem to be the magic combination.
We were also noticing another issue with the stainless steel glue in bolts that we first noticed with the expansion bolts. Even the glue in bolts there braking right were the glue had stopped covering the bolt on the outside of the hole. This lead us to believe that even if we got complete coverage with the glue inside the whole the exposed metal would still be susceptible to the atmospheric (salty air) corrosion. Now with the knowledge that we now have the Titanium bolts should with stand any corrosive elements that Thailand can throw at them. But just to make sure we have decided the best course of action would be to stick with the Hilti RE-500 glue with the combination of the Titanium bolts. This combination is hopefully the last step in a two decade long process to find a solution to the bolt problem in Southern Thailand.