/ Karabiner gate corrosion

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oldie 22 Mar 2020

I have a snapgate krab which has obviously seen a deal of use but the main body is completely uncorroded. However the gate alone is badly corroded, grey and flaking. From academic interest only I wonder what the reason is. Is the gate likely to be a different alloy? Presumably the gate is hollow to contain the spring and could this trap eg salt water and cause the visible corrosion on the outside?

From Vaude "LUCKY" quickdraw, the other krab is OK. CE-0129, 06-A-188970, usual three KN values. Bought second hand in a garden charity sale. Almost certainly previously used on coastal cliffs. I'm NOT intending to use it for climbing (though presumably the 8KN open gate rating would still apply).
 

Post edited at 11:26
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Wil Treasure 22 Mar 2020
In reply to oldie:

The gate itself is probably the same grade of aluminium as the rest. Inside the gate however you will have different metals, steel for the spring and pins and possibly different grades for the other moving parts. This can cause galvanic corrosion, especially when used near the sea.

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oldie 22 Mar 2020
In reply to Wil Treasure:

Thanks. Hadn't considered the spring. The pin is also in contact with the main body and there's no sign of corrosion on that.

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Wil Treasure 22 Mar 2020
In reply to oldie:

It's interesting how they corrode. The particular metals in contact make a big difference.

A friend found a krab on a sea cliff years ago that was severely corroded, pits and holes in both body and gate. It was a model that had only been released 2 years earlier so hadn't been on the cliff that long. I encouraged him to send it to DMM to see how strong it was (I reckon we could have broken it with a good bounce). He kept it as a souvenir though.

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oldie 22 Mar 2020
In reply to Wil Treasure:

I forgot to mention that the snapgate at the other end of the QD was completely uncorroded, so presumably the poor one had been in a salty puddle or something and not properly rinsed.

i bought a batch of six alloy Salewa karabiners when I started lead climbing to supplement my steel ones. One weekend I forgot to rinse my gear after sea cliff climbing and after a week or so most were flaking badly (still in use on my washing line etc). On the other hand I had a large Stubai krab that I mistakenly left while reversing a traverse to the back of a sea cave, three weeks later I was back and retrieved it.....slightly dulled, but I still use it occasionally. Presumably just alloys of different susceptibility..

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dobby 200 22 Mar 2020
In reply to oldie:

https://i.postimg.cc/4xG0FDGy/carabiner-rot.jpg

That is retired carabiner I found at a highropes course being used to hold crate stack crates away. It was 10 meters from the sea.

Left was how I found it. Right was after gently rubbing the flaky material away. After the photo the gate completely crumbled when I tried to move it.

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oldie 22 Mar 2020
In reply to dobby 200:

More impressive than mine. Interesting that, like mine, the main body was OK, although in contact with the gate. Presumably the oxide layer on the alloy surface (increased by anodizing I imagine) acts as insulation between gate and body. Possibly the spring's movement continually scratches oxide off the inside of the gate plus salt water may be trapped inside which removes the protective oxide? (vague memory from school chemistry teacher).

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