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Mixed metals in a bolt set up (but not one that'll ever kill anyone)
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Nov 11, 2012
Stairway to Heaven (pitch 3)
A disclaimer first: fortunately, the mistake I am about to describe was made in a place that will be of no consequence to anyone other than me-- a private, indoor wall. Therefore, no other climbers were/will be harmed in the making of this film.

So, I put a pair of bolts w hangers into my basement climbing wall. Sort of an anchor spot for practicing rigging and various belay set ups and such (I've got kids who are/will be learning to climb, and I also like to brush up my own systems knowledge before big objectives and when it's been too long). I bought my first set of plated steel bolts and hangers (both Fixe) for this purpose. Everything else I have ever placed outside or have in my stash for future placement outside is stainless steel. Only the best when everyone else's a$$ is on the line.

Unfortunately, when it came time to place the set up, I grabbed the wrong hangers. I drilled through the 3/4 plywood, 1/2 inch of insulation, and into the concrete as far as I could go. Then I placed the 1/2" by 4 1/2" bolts with hangers. Once I finished tightening the bolts, I stool back to admire my work and saw my mistake. Now I have stainless steel hangers on plated steel bolts. I am loathe to take the bolts back out unless it is absolutely necessary, since it is not something I have ever done before, and I fear losing the expansion nut in the back of one of the holes, rendering them useless and forcing me to drill more holes in my wall.

Now, these bolts are for practice/demonstration purposes only, so 1) they will rarely hold weight, 2) the only people who will use them are me and my family and perhaps a couple of friends as nerdy about this stuff as I am, and 3) the furthest they could drop anyone is a few feet onto the pads at the base of the home woody. No harm, no foul.

Therefore, I am mostly just curious: in a dry, indoor setting, will galvanic corrosion still occur at all? Will it occur but at a slower rate without any moisture to facilitate the ion exchange? Is that how galvanic corrosion occurs? How long will it take in these near-laboratory conditions for the corrosion to significantly affect the holding strength of the bolt and/or hanger? Should I simply write back to everyone in a few dozen years when the bolt heads finally pop off? That might be like waiting for the answer to how many licks it takes to get to the center of a Tootsie Pop...

Oh, and just to get it out of the way: I'M GONNA DIE!!!!!
Josh
From Golden, CO
Joined Jan 26, 2006
562 points
Nov 11, 2012
Wow, MP threads have really gotten this bad...

And, why not just swap out the hangers if you're so worried about it. Rawl 5-piece studs are removable and replaceable, that's the whole point of the bolt.
chosspector
From San Juans, CO
Joined Oct 19, 2008
1,289 points
Nov 11, 2012
Stairway to Heaven (pitch 3)
Ooookay, people. I thought I made it clear no one is worried here. I hoped to use this opportunity to learn something about how the chemical process works. This is not something most of us learn in school without a degree in metalurgy or materials engineering. Josh
From Golden, CO
Joined Jan 26, 2006
562 points
Nov 11, 2012
To get galvanic corrosion you need an electrical connection between the two metals and an electrolyte to transfer the ions. If there is no fluid then corrosion will not occur. Jim Titt
From Germany
Joined Nov 10, 2009
185 points
Nov 11, 2012
Which way again?
The trolling is getting out of hand. And I'm referring to the replies, not the OP.

Josh, you can untighten those bolts, switch out the hangers, and re-tighten, no problem. You won't lose anything.

The retards are right that you shouldn't stress this at all, but why not use cheap stuff for your demo setup? Kudos for being able to take a joke and for bothering to be aware of mixed metal issues in the first place. Post up how your hanger switch out went so someone else who hasn't done this and is wondering can calm their nerves and save a thread. Good luck.
Cunning Linguist
Joined Feb 15, 2007
2,478 points
Nov 11, 2012
Obi Wan Ryobi - Darth Vader Crag, Rumney NH
My anchor setup at home is 3/8" holes (?)in plywood with 5mm cord doubled to make a loop, and tied with a stopper knot, then fed through the hole from behind. I'm not sure why you needed bolts? Brendan Blanchard
From Boulder, CO
Joined Oct 18, 2010
309 points
Nov 11, 2012
yaak crack Red Rock Canyon, NV
Didn't Josh explain that the bolts were plated, not the hangers? Why is everyone telling him to switch out the hangers? I confused.

Edit; oh, never mind I just read up on galvanized corrosion. Makes sense now.
Jon Zucco
From Denver, CO
Joined Aug 15, 2008
357 points
Nov 11, 2012
The Cathedral Spires in RMNP, left to right: Stile...
Brendan Blanchard wrote:
My anchor setup at home is 3/8" holes (?)in plywood with 5mm cord doubled to make a loop, and tied with a stopper knot, then fed through the hole from behind. I'm not sure why you needed bolts?


I'm not sure why you need a home anchor setup.
Marc H
From Lafayette, CO
Joined May 10, 2007
280 points
Administrator
Nov 12, 2012
Josh wrote:
Ain a dry, indoor setting, will galvanic corrosion still occur at all?

No. Generally you need some type of liquid to act as an electrolytic fluid, such as water. Dont worry, it will be fine.
20 kN
From Hawaii
Joined Feb 2, 2009
665 points
Nov 12, 2012
Stairway to Heaven (pitch 3)
Thanks for the info, all. I appreciate the tutorial on the galvanic process. I'll switch out those hangers at some point, when I get around to it, but it sounds like there is no hurry... Josh
From Golden, CO
Joined Jan 26, 2006
562 points
Nov 12, 2012
Stabby
As long as you do it sometime in the next 3-400 years its all good. Mike Lane
From Centennial, CO
Joined Jan 21, 2006
839 points


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