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Dingus McGee
Social climber
Laramie
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Topic Author's Original Post - Oct 17, 2011 - 10:56am PT
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Modified Steel Anchor Bolts in Rock—Can They Outlast Stainless Steel?
In 1994 I placed a box or so of carbon steel Red Devil 3/8” sleeve bolts in Reese Mtn granite with the intention of preserving them to extend their life. My method was ENCAPSULATION with RTV Silicone Sealant.
Now, I have no desire to hear the nightmare failures of those that tried to SEAL-THE-SURFACE of such installations. The process I used is different than just sealing the surface region around the bolt.
A partial inspection of two of these Silicone Encapsulated bolts was done 17 years later at Reese Mtn inadvertently when replacing homemade angle iron hangers with more modern pricey contraptions. After removing the nut from the bolt our difficulties began because the hanger/washer was tenaciously glued to the rock and bolt. Some silicone was cut away from the area surrounding the bolt/rock interface. Examination of both the bolt at the rock surface and the old steel hanger showed no (zero) signs of rust or corrosion. In fact the bolt surface looked brand new. Bolt/hangers not silicone treaded in this climbing area do show slight signs of rust at these locations. The bolts were not removed from the hole but they had been ENCAPSULATED with Silicone RTV sealant. Were they rusting in the hole? Does silicone encapsulation corrode the bolt stock in bolt holes? To look at this aspect, the bolts would have to be pulled from their holes.
This weekend I decided to test an additional procedure to the encapsulation process that would result in pressurization of the encapsulation fluid during the final phase of bolt tightening. The item needed to achieve this was a 5/8” rubber hose washer placed under the bolt hanger. The washer did work as expected in that silicone was forced out of the washer sides during the final tightening thus increasing the likelihood of a good encapsulation job.
In the photo you can see I used silicone and polyurethane sealant. The silicone is easier to work with than poly U but maybe not be as strong. The rock is orthoquartzite and quite fine grained. None of the bolts place at Reese Mtn were slippers. The bolt shown here on the right placed in poly U was a slipper in that it took many tries to get the sleeve to seize. I suspect tough fine grained substrates to create more slipping problems i.e. not able to reach torque.
This method differs from glue-ins in that a mechanical type anchor is used and a bigger difference is that during stud drive-in (if you have used a close tolerance drill bit ) hammer blows to the bolt result in pressure waves transients on the sealant (hydrostatic pressure) forcing the sealant into the rock surface around the bolt bore.
My Question, since I do not live in an environment where hydrogen embrittlement of stainless steel occurs, could this method be used to enhance bolt life along such coastal regions?
Mighty Hiker, before blah-blahing on this please read the UIAA Blah-BLAHING of this and give us a report on your home work?
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WBraun
climber
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Oct 17, 2011 - 11:03am PT
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Interesting and thanks for posting this.
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Toerag
Trad climber
Guernsey, British Channel Islands
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Oct 17, 2011 - 11:20am PT
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One potential problem - is you use PU sealant (sikaflex or suchlike) the strength of the sealant may mask bolt failures. In my experience bedding bits of boat together with sikaflex results in the destruction of one or other part when you try to disassemble them.
In reality you should give up on expansion bolts and use glue-ins - read the boltproducts website for some good info.
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 11:27am PT
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Toerag,
Tom Kelley, a rock mechanics engineer (and climber) from Fort Collins, a few years ago informed me that no glue-in bolt company would warranty their glue-in bolts in freeze-thaw conditions.
We have no intent to disassemble these anchors.
If the PU sealant is strong enough to withstand nut tightening torque and tension with a failed sleeve then I suspect the bolt could easily withstand a high shear load and we would be getting some redundancy by using it?
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Russ Walling
Gym climber
Poofter's Froth, Wyoming
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Oct 17, 2011 - 11:29am PT
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Thats attractive.....
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 11:47am PT
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Bruce K,
we are talking about ENCAPSULATION (nut and all) not just some sealant used. And who did what you are reporting?
I think galvanic corrosion can not pass through silicone?
Hydrogen embrittlement occurs with stainless steels when they are used in a warm humid coastal region (seaside) with chlorine and water (vapor?) somehow enhancing the weaking of these stainless steels (this effect happens less with 316 than 304) Surprisingly these S steels are not quite what we think we think of them as being.
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apogee
climber
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Oct 17, 2011 - 11:59am PT
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I'm no engineer either, but in the world of construction, it's a well-understood standard that sealants always eventually fail. In protecting any penetration to a building (i.e. windows/doors), providing some way for water to exit is a primary strategy against rot & failure.
Possibly an apples & oranges comparison, but the concept seems apt.
These discussions are quite interesting, and much appreciated.
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Forest
Trad climber
Denver, CO
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Oct 17, 2011 - 12:02pm PT
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In particularly bad areas (thailand is the one I've seen), I've seen the stainless hanger itself rust away in a ridiculously short amount of time.
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 12:03pm PT
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Bruce K,
yes, I would think epoxies are too brittle. The seal around the steel is far more important than around the rock. So if you don't get good rock surface bonding (maybe from the rock always being damp) can you get good bonding on all the steel?
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 12:07pm PT
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Forest,
hanger corrosion in several years? I had no idea corrosion there was this harsh. Can the hangers be encapsulated?
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 12:14pm PT
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apogee,
yes, sealants always fail before the end of cosmological or geologic time. I think that we would be better off looking at this problem more like construction installers do. "Do sealants help in the construction business?"
I think that if these sealants prolong bolt anchor life by even 2x they are worth the hassle.
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Moof
Big Wall climber
Orygun
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Oct 17, 2011 - 12:24pm PT
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Can't speak from direct experience regarding bolts, but in the aerospace industry there is an expression about things that are almost hermetic. "Once in, never out." You are best off making something either entirely laser welded air tight, or leave it wide open to the elements. All other options end up being disasters due to trapped moisture.
As mentioned from the Squamish fellow, the concern when dealing with moisture related issues is trapping of moisture next the to the surface. Back in the hole your bolts have to have metal to rock contact, breaching your "encapsulation". Any water that gets in back there is likely corroding away right where it matters most, at the cone. At the surface where you inspected, you will likely never see corrosion till the day the thing falls out in your hand with a rotted off cone. Given that the glue is so tenacious, that will likely require someone to whip on one, and let's hope they don't rip a whole pitch of your bolts when they do. Heck, a lot of old fixed pitons look just fine till a cleanup crew gives them a tug, only to get a rotted off stump in their hands.
My completely uninformed $0.02.
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wstmrnclmr
Trad climber
Bolinas, CA
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Oct 17, 2011 - 12:26pm PT
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I'm a sheet metal man and have seen just about every type of metal and caulk there is go through the coastal environment. Hippy construction in Bolinas has thrown together every conceivably screwed up combo of everything you can think of. I've replaced bolts that had all sorts of contrivances directly on the coast (Mickeys Beach,etc.) and caulk does not work in the coastal environment. UV, rain, and freezing blow off even exposed epoxy.....Only stainless glue in types last. Stainless hangers and carbon steel are compatible by the way. Stainless is compatible with just about anything especially if it's 316. Also, if water gets behind caulk, it can trap water and keep it from drying out for a while. Five piece rawls guts are nickel or galv and rot out regardless of whether stainless bolts and hangers are used. Also, RTV silicone has vinegar (that's right vinegar, you can smell it)and can be corrosive to certain ferrous metals. Silicone was developed for glass and plastics. OK to use on an engine block that's warm and protected. Also, as Walleye said, "attractive"......looks like somebody took a dump on the cliff. So, no way can any contrivance of steel outlast a glue in SS bolt on the coast or anywhere else with today's technology.
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 12:27pm PT
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Bruce Kay,
one measure of seawater immersion corrosion is the galvanic potential. The greater the difference in galvanic potential of two contact metals the faster corrosion occurs.
Metals with even slight differences in alloying metals added and quenching rates have slightly different galvanic potentials. 316 Stainless steel is somehow different than 304 and 316 does better around seawater environs than 304. It does cost more. Are any hangers made of 316 commercially available?
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 12:36pm PT
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wstmrnclmr,
there is an advertising law prohibiting the use of the word "sealant" on "caulk" like materials that do not meet some USA's agencie's specifications on what can be labeled as sealants. I can put little faith in your testimony about the beech construction you attest to having seen as to good evidence of why this method will not work.
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 12:40pm PT
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Moof,
any trapped moisture and other agents have only a little reagent power (mass) to corrode and alter steels. When they are comsumed (by converting steel to rust) they are chemically locked up and have no more destructive power. The process ends at this point.
it seem you are assuming the sleeve mushes out all silicone in the rock/silicone/steel interface when tightened. Does this happen?
Again our real question here is, "Can we double the life expectancty?"
If this all or none methodology is what the aerospace industry uses sent back my tax dollars.
We are nuts if we think any remedy will last for geologic time.
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apogee
climber
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Oct 17, 2011 - 12:46pm PT
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"Do sealants help in the construction business?"
Yes, but as a general principle, they are only one of at least a couple defenses against water intrusion. There is usually some kind of backup strategy that allows any moisture that might penetrate the sealant to escape and dry. In construction methods, this means creating intentional drainage planes in the overall design of the building 'skin', and various flashing methods to direct water out & away.
I guess the pertinent concept is that no single strategy is counted on as complete protection- there's always some kind of back-up strategy should the first one fail (in this case, sealants).
Edit:
"We are nuts if we think any remedy will last for geologic time. "
We're probably also nuts if we think any one strategy will work on all rock, in all areas of the world.
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 12:49pm PT
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apogee,
if you leave a way for a "failed sealant" to drain if it fails most likely it was not an encapsulation method of using a sealant in the first place, because you had designed an opening for the water or whatever to go.
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Dingus McGee
Social climber
Laramie
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Topic Author's Reply - Oct 17, 2011 - 12:53pm PT
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apogee,
We're probably also nuts if we think any one strategy will work on all rock, in all areas of the world.
I say we are foolish if doubling the life expectancy is of little concern.
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Moof
Big Wall climber
Orygun
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Oct 17, 2011 - 01:02pm PT
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Clearly you have a scientifically proven bolt-life doubling cure all available cheaply at your local Home Despot, and nobody will dissuade you from that conclusion.
Perhaps if you disassembled at least one of your old bolts and performed a proper postmortem I might care. Using random combos of materials together tends to end badly more times than not, and no amount of internet ranting is likely to change that.
At the very least, thank you for making your experiment plainly obvious for the rest of us to avoid. Re-bolters are going to curse your name however.
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