Mixing metals

evo

evo

Been here much more than a while
Location
My Island, WA
Some where some how I managed to get it ingrained in my head that mixing alloys is a very bad thing. That one should never use a steel biner or clip on a aluminium ring, or pulley. Does this have any merit in the climbing world.
Personally I love having a petzl oxan steel biner on the end of my rope to heave my line higher, only adding a throwbag if necessary. I also use a dmm steel oval on the end of my flipline, to the alloy ring on my TM. I've also seen manufactured gear that just comes this way, such as the wire core lanyards with the alloy snaps.
What are ya'lls thoughts on this? Am I just over thinking again?
 
evo said:
Some where some how I managed to get it ingrained in my head that mixing alloys is a very bad thing. That one should never use a steel biner or clip on a aluminium ring, or pulley. Does this have any merit in the climbing world.
Personally I love having a petzl oxan steel biner on the end of my rope to heave my line higher, only adding a throwbag if necessary. I also use a dmm steel oval on the end of my flipline, to the alloy ring on my TM. I've also seen manufactured gear that just comes this way, such as the wire core lanyards with the alloy snaps.
What are ya'lls thoughts on this? Am I just over thinking again?
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I think that technically we aren't supposed to do it, but the risk of steel gouging aluminum isn't something that concerns me. It won't be instantaneous. Inspect your gear.
Any risk of galvanic corrosion from mixing metals is far less than the chance of the alloying metals in your aluminum carabiner reacting amongst themselves (basically a non issue).
 
Not a good idea to have both clanging around in the same ditty bag, but as far as using both in your climbing system go for it.
 
Gosh when I read the title, I was thinking galvanic reactions which generally are bad as they eat one or both metals away with corrosion - overtime. So maybe that is the little mantra you are playing telling you it is not good. But in climbing, as Boomslang offered...go for it.
 
I was under the impression it has more to do with hardness levels not corrosion. A very hard steel is potentially very rough on soft aluminium.
 
JeffOpar said:
I was under the impression it has more to do with hardness levels not corrosion. A very hard steel is potentially very rough on soft aluminium.
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We don't deal much with soft aluminum.
I think all of my work-related aluminum is heat treated and much of it anodized, although I could be forgetting something.
Anyway, 7075 t6 aluminum is at least as hard as mild steel. I am actually unsure of what alloy our carabiners are made of. And our rings and figure 8s. Anybody know that or what process they use to make them?
 
JeffOpar said:
I was under the impression it has more to do with hardness levels not corrosion. A very hard steel is potentially very rough on soft aluminium.
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Not that the steel swivel snaps found on lanyards are hardened steel, but I am changing the aluminum positioning rings to stainless. Not only for wear resistance, but I ordered them a little bit larger for ease of clipping into them with a lanyard. Also easier to identify which ring is which on my MCRS.
 
Hi Evo,

Steel carabiners have been used with aluminum pulleys, rigging plates, rescue 8's and what-have-you in technical rescue for ages. Until about 10 years ago you could not buy an aluminum G-rated carabiner and they were all steel. Even with the advent of aluminum G-rated carabiners, steel probably outsells them 50 to 1.

I found this picture on SMC's website and it shows a typical use of a rigging plate in technical rescue:


rigging_plate_rescue_system.jpg


Pulley side plates are aluminum, the cam in the rope grab is aluminum, as well as the rigging plate. Carabiners are steel.

Maybe all of this doesn't carry over into tree work, but I'm guessing most of it does. Maybe an exception might be with dynamic loads like in negative blocking?

Hope this helps.

Mark
 
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merle_nelson said:
Something Witty - more info to follow this weekend. A guy who knows enough about it to write intelligently about it said he would probably be able to chime in then.
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Cool. I'm looking forward to it.
I have always been weird about old steel fliplines because you can't inspect them properly.
 
I am looking forward to the steel fliplines.

I personally have always mixed metals for my climbing system. I know that it's taboo in some industries, and I might have just gotten it beat into my skull from living on the shore of the pacific most my life. I have seen increased wear on my hitch climber pulley where I snap into with the steel carabiner.

What about the CMI blocks with stainless side plates, steel bolts, aluminium sheaves, and bronze bushings? I'm not trying to pick things apart, nor criticize, just curious on others thoughts on this. The only time I've had a corrosion issue is from leaving a bundle of omega biners buried under a pile of brush that was speedlined out. I forgot about them for a few days, and I think they reacted with the grass. I've also noticed some tools left in the chip box with chips corrode very quickly, such as fiber glass pole couplers around the steel and aluminium.

These little things just keeps reinforcing the voices in my head. However I do take decent care of my life support and rigging. It's not uncommon to be working within a short stone toss form the beach.
 
Tom is spot on. Unfortunately, there is at least one steel core flip line that uses copper (swags?) and then covers them with black plastic heat shrink.

Add moisture, add time, equals....

A more informed voice should chime in this weekend.
 
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