The Bolting End-Game
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bus driver wrote:Is there any non destructive testing methods for carbon steel bolts ? Ie could you run a current and map it to see how much mass is left. This could be compared to known specs. Good bolts could be left for future testing and corroded bolts could be pulled. Now, anything with surface rust is assumed junk but people seem to agree that surface corrosion does not equal weakness.You can pound on the hanger a bit with a hammer. We used to do that to test for SCC in stainless steel hangers back when we had a bunch of SS hangers that were still in use. However, hitting the hanger with a hammer tests the hanger more than the bolt unfortunately. |
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Dan Merrick wrote:DrRockso- Thanks for the video link. Looks like he has the core bit working. When I have tried, the bit drifts off the bolt and eventually slices through the bolt making the lower hole oversize and pretty much useless. The rock he is working with looks soft and part of the trouble I have had may be due to working with hard granite and the bolt is easier for the bit to cut than the rock. Also, since power tools are not permitted in National Parks (Yosemite) and in wilderness areas, this won't help rebolting efforts in these areas.He is drilling in Nuttal Sandstone in the New River Gorge, perhaps not the hardest rock but certainly the hardest of the sandstones, approaching the hardness of some granites. As far as power tools in national parks, in some cases it may be best to use mechanical still, in other cases glue ins may be better and we can worry about removing them 50-100 years from now. |
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good evening everybody, |
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beaki wrote:I remember that Pit Schubert ( theuiaa.org/pit-schubert.html DAV Safety Commission) conducted a survey if professional mountain guides can assess pitons ... and they could't. it was just too hard. while bolts are likely to be safer than pitons, its probably impossible to tell if the person who put them in screwed up.Both pins and bolts require maintenance over time. And you are correct, you can't be sure about either a pin or a bolt just looking at it. You need a hammer to test a pin and the only way to be 100% positive about a bolt is to remove it. And, much like bolts, how well pins perform over time varies greatly with rock type and climate. At the crag where I replaced the anchors the pins on average way out performed the bolts by decades. |
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rocknice2 wrote: While I've had similar results as you using carbon bolts and stainless hangers, I don't think the next 10 years will be nearly as kind as the first 20.I don't disagree, but I don't have experience beyond what I shared. How many times have you heard someone, perhaps with no real knowledge, telling us how we should never "use stainless and carbon together". That might be true in a salty environment but certainly wasn't true in the Nor Cal central valley, at least for the last 25 years. At the time we didn't know any better but today I use all stainless. It's simply the best choice in my area. Selfish? I don't agree. I've replaced many bolts that I didn't put in. The community damn well better be prepared to inspect and replace my bolts 25 years from now. I'm 66 years old and if I'm still around at 91 I'm gonna be chasing old woman not fixing climbs. Brad |
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rockvoyager wrote: How many times have you heard someone, perhaps with no real knowledge, telling us how we should never "use stainless and carbon together".They were telling you correctly. Galvanic corrosion is a real thing and it occurs well outside marine environments. It's so common that a quick search on Google yields hundreds of photos of crap hangers and bolts: https://www.google.com/search?q=galvanic+corrosion+climbing&biw=1280&bih=556&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMIs7mxo-uWyQIVB91jCh1H9AuZ#imgrc=_ Here is what Fixe says: If you are placing plated steel bolts PLACE plated steel hangers or anchors. Mixing types and grades of steel can promote deterioration. A stainless hanger will not indicate possible corrosion of the plated steel bolt. FIXE plated hangers are as strong as any of the competition's stainless models. fixehardware.com/shop/mixin… You may have gotten away with it at your local crag, but it's still a real issue. I have seen bolts in crags ranging from El Potrero Chico to Squamish and Red Rocks to Seneca suffering from galvanic corrosion-it's an issue almost everywhere. |
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20 kN wrote: You may have gotten away with it at your local crag, but it's still a real issue. I have seen bolts in crags ranging from El Potrero Chico to Squamish and Red Rocks to Seneca suffering from galvanic corrosion-it's an issue almost everywhere.I just don't buy that galvanic corrosion is a problem everywhere. I have been rebolting in California and Colorado for over 28 years and I have never seen it in any of the bolts I have replaced(500+). It is very common to see plated bolts with SS hangers. The bolts, even after 15 years of being in a 'mixed metal' environment, test out at 5000lbs in shear which is the rated strength new. |
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Healyje wrote: Both pins and bolts require maintenance over time. And you are correct, you can't be sure about either a pin or a bolt just looking at it. You need a hammer to test a pin and the only way to be 100% positive about a bolt is to remove it. And, much like bolts, how well pins perform over time varies greatly with rock type and climate. At the crag where I replaced the anchors the pins on average way out performed the bolts by decades.With wedge bolts you only need to loosen the nut and re-tighten it to the appropriate torque, they are torque-controlled anchors. |
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Jim Titt wrote: With wedge bolts you only need to loosen the nut and re-tighten it to the appropriate torque, they are torque-controlled anchors.Sure, but most of the bolts I replaced would no longer tighten due to corrosion. |
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Healyje wrote: Sure, but most of the bolts I replaced would no longer tighten due to corrosion.So they are so corroded you can´t remove the hanger for inspection nor tighten them to check if they hold, what else is there to know except they are no longer acceptable? |
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Bruce Hildenbrand wrote: I just don't buy that galvanic corrosion is a problem everywhere. I have been rebolting in California and Colorado for over 28 years and I have never seen it in any of the bolts I have replaced(500+). It is very common to see plated bolts with SS hangers. The bolts, even after 15 years of being in a 'mixed metal' environment, test out at 5000lbs in shear which is the rated strength new.My thoughts and experience exactly. Thx Bruce! |
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Here are some shots from American Fork. My guess is that we are seeing galvanic corrosion <5% of the time. Most all of the placements are SS hangers/plated rawl sleeve bolts around 25 years old. They have been solid which is reassuring, but all of the plated bolts, even some newer ones, are corroding in the limestone. |
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jonathan knight wrote:Here are some shots from American Fork. My guess is that we are seeing galvanic corrosion <5% of the time. Most all of the placements are SS hangers/plated rawl sleeve bolts around 25 years old. They have been solid which is reassuring, but all of the plated bolts, even some newer ones, are corroding in the limestone. The control from the same route: Not a very good comparison, but here's some 304 SS. The reassembled bolt was <10 years old, and the rest were around 12 years in the rock. There's no rust from what I can see.Just as an FYI, just because the bolt is corroded outside the hole doesn't mean that galvanic corrosion is what caused it to corrode. That could very easily just be uniform corrosion over the bolt head as well. The only way to tell if it's galvanic is if the only corrosion is on the surface between the bolt head and the hanger. I'm not saying that galvanic corrosion didn't speed up the corrosion of the bolt pictured, but it is entirely possible (and highly likely) that the bolt pictured as being galvanic corrosion had very little if any galvanic contribution to the corrosion. |
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Like this? |
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kennoyce wrote: The only way to tell if it's galvanic is if the only corrosion is on the surface between the bolt head and the hanger.That is contrary to what I understand about galvanic corrosion. I thought that in galvanic corrosion, one material corrodes before the other does. Like when they bolt zinc blocks to the hulls of steel ships. The zinc corrodes first and the steel doesn't until the zinc is gone. One metal acts as anode and the other as cathode which has nothing to do with the contact except that the contact must conduct electricity. |
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Dan Merrick wrote: That is contrary to what I understand about galvanic corrosion. I thought that in galvanic corrosion, one material corrodes before the other does. Like when they bolt zinc blocks to the hulls of steel ships. The zinc corrodes first and the steel doesn't until the zinc is gone. One metal acts as anode and the other as cathode which has nothing to do with the contact except that the contact must conduct electricity.You're understanding is primarily correct, but the important thing to understand about corrosion is there is never only one scenario that can occur. In my experience, galvanic corrosion can start localized, affecting the material between the two dissimilar metals, but then it spreads, possibly even encompassing the entire affected part depending on how large the part is. What the bolt would look like would depend on when you viewed it. If the corrosion process is in its early stages, it is possible only part of the bolt would be effected. If you catch it in it's later stages, likely the entire bolt would be effected. I suspect in most cases climbers catch the bolt in its latest stage of corrosion since we dont typically replace shiny bolts. |
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Dan Merrick wrote: That is contrary to what I understand about galvanic corrosion. I thought that in galvanic corrosion, one material corrodes before the other does. Like when they bolt zinc blocks to the hulls of steel ships. The zinc corrodes first and the steel doesn't until the zinc is gone. One metal acts as anode and the other as cathode which has nothing to do with the contact except that the contact must conduct electricity.You are correct, but the problem is that a ship is much different than a bolt due to the fact that the ship is continuously submerged in an electrolyte. For galvanic corrosion to take place there must be an electrolyte present (i.e. water or even better, salt water). The electrolyte must form an electrical pathway between the two dissimilar metals which works perfectly on a ship. However, in a climbing bolt the only time that there is an electrolyte present is generally when it rains and this quickly dries on the exterior of the bolt head and the hanger. The place where the electrolyte remains so that it can cause galvanic corrosion is generally just between the bolt head or washer and the hanger because the moisture becomes trapped there and may take a long time to dry out. This is why you can really only tell if it's galvanic corrosion if it is located just between the bolt head and the hanger, otherwise you really don't know if it is galvanic or just uniform corrosion. It is entirely possible that the corrosion started as galvanic until the zinc plating was sacrificed, and then uniform corrosion took over from there, but it's really not something that you can tell just by looking at it. |
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kennoyce wrote: an electrolyte present (i.e. water or even better, salt water)...Air is an electrolyte. |
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Jeremy in Inyokern wrote: Air is an electrolyte.No, just no, air does not conduct electricity. |
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kennoyce wrote: No, just no, air does not conduct electricity.A vacuum does not. Air is a lot of different things. If air was not an electrolye all you would have to do to protect metal would be leave it outside. |