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Chockstone Forum - General Discussion

General Climbing Discussion

Author
Stainless hangers 304 or 316
Tastrad
7/11/2012
11:13:22 AM
How would 304 stainless hangers go on a 316 stainless bolt in a sea cliff?

rodw
7/11/2012
11:43:25 AM
I always thought you shouldn't mix, doubly so on a sea cliff...Im sure someone will have a more scientific oppinion to it though.
mikllaw
7/11/2012
11:47:01 AM
as the metals are slightly different there could be slight long term corrosion, but this publication
www.npl.co.uk/upload/pdf/bimetallic_20071105114556.pdf
says corrosion is unikely.

shortman
7/11/2012
11:52:09 AM
They would be more prone to corrosion/oxidization??
Tastrad
7/11/2012
1:22:36 PM
So Mikl, do yu think 304 hangers would be ok on a coastal cliff? I know 316 is non-negotiable for the bolt

Climboholic
7/11/2012
1:55:04 PM
Without any analysis, I doubt dissimilar metal corrosion would be an issue between different alloys of stainless steel.

Big G
7/11/2012
1:55:23 PM
surely if you put a 316 u-bolt in then you eliminate the potential for galvanic action to occur
SHONKY
7/11/2012
3:15:20 PM
304 STAINLESS SHOULD NOT BE USED NEAR SALT WATER
mikllaw
7/11/2012
5:11:05 PM
The hanger has more surface area exposed and is a lot thinner, so probably requires better corrosion resistance than the bolt. Much of the corrosion talk is also about appearence, all my old stainless on the sydney seacliffs (a mix of 304 and 316) looks speckly and very lightly rusted, but is probably fine.

Did you get the 304 for free? I'd keep the 304 hangers for inland and buy 316 for the sea.

nmonteith
7/11/2012
9:57:24 PM
I've certainly seen noticeable corrosion on 304 stuff I have placed on sea cliffs.
Tastrad
8/11/2012
8:55:56 AM
Thanks for your advice. However, I can't find anyone selling 316 stainless hangers in Australia except PFH who have a marine grade stainless hanger - but they are not very nice hangers - a bit sharp on the edges. I guess 316 u-bolts are the best option
pecheur
8/11/2012
9:21:53 AM
On 8/11/2012 Tastrad wrote:
>Thanks for your advice. However, I can't find anyone selling 316 stainless
>hangers in Australia except PFH who have a marine grade stainless hanger
>- but they are not very nice hangers - a bit sharp on the edges. I guess
>316 u-bolts are the best option

From my reading when I was bored in Thailand, I was under the impression that all Petzl hangers are 316. Certainly all the Petzl gear left in the cliffs there still looked shiny (enen if it was possibly stuffed internally). I can't say I tested it, but they certainly looked better than the 304 stuff also still left in the cliffs next to the Ti stuff.
Jim Titt
9/11/2012
6:05:36 PM
The dissimilar metal aspect is pretty well irrelevant.
The hanger will usualy start to fail under the nut where you canīt see it.
Petzl hangers are 316.
Glue-ins are far superior in corrosion resistance as they have no stress raisers and no hidden pockets to collect stagnant, corrosive water. Given the choice between a 304 glue-in using an unwelded design and a 316 bolt/hanger I would choose the glue-in every time and this is what we recommend to our customers.
Welded-eye designs have proved not to be as satisfactory as the post-weld treatment often fails to passivate the material in the heat affected zone.

There are 13 messages in this topic.

 

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