Rust on stainless bolts
8 April 2010 - 10:51pm
I was climbing on the West coast over Easter and noticed a significant amount of rust on newly placed stainless bolts and hangers. The bolts where 10 by 90mm tru bolts (316) with a range of different hangers. They where placed 15 months ago in an area that is 2km away from the Coast. I’m interested to hear if other people have had similar experiences?
8 April 2010 - 11:55pm
#3
hhhmmmm, does sound like galvanic corrosion. Will be curious how they look in 5-10 years (especially behind the hanger).
9 April 2010 - 1:25pm
#5
Anyone else out there a tad concerned about clipping stainless expansion bolts at sea crags after reading that (thinking Charleston, Lovers Leap specifically).
9 April 2010 - 5:53pm
#6
Having seen the (remenants of) bolts at Charleston, I was concerned about clipping stainless expansion bolts at sea crags long before reading that.
9 April 2010 - 8:38pm
#8
In NZ, if I remember correctly, stainless started being used in the late '90s.
I am not sure which areas were first though.
When we rebolted Three's Company at Britten (originally bolted in 2000), I distincly remember removing an almost completely disinigrated (non-stainless) hanger from a stainless bolt. We didn't pull the bolt, so I can't vouch for its integrity, but it looked to be in somewhat better shape than the hanger.
Pretty crazy seeing how much corrosion could occur in 6 years when metals get mixed in a wet environment.
I am not sure if there have been any cases of chloride stress corrosion cracking in NZ, but it would be interesting to test some of the stainless bolts that have been around a while at places like Charleston and Lovers Leap.
From some other things I have read about corrosion cracking, the bolts don't need to have been in place for very long before they become severly weakend. 5years+ is definitely long enough if in a number of cases.
11 April 2010 - 8:27am
#9
There is surface stain and corrosion. People get them confused. Just because it is discoloured doesn't mean it is rusting. Think surface patina
16 February 2011 - 2:01pm
#10
After reading the Devil and the Deep Blue Sea article and then the NZAC Bolting Technical Guidelines (Updated November 2005) I would suggest that NZAC removes the reference to sea crags in the expansion bolts paragraph and adds "or sea crags" after "Shouldn't be used in roofs".
Who would one contact in regard to this?
16 February 2011 - 8:26pm
#11
contact NZAC Office
16 February 2011 - 10:05pm
#12
Have done a bit more reading on CSCC, it seems the rate of CSCC doubles for every 10 degree increase in temperature. Possibly an explanation for the lack of problems so far in NZ. I'm guessing Thailand would be at least 10 degrees warmer on average than most of NZ, so we could therefore expect failures after twice as long...
16 February 2011 - 10:21pm
#13
No one really seems to be able to understand Thailands situation exactly. Even marine grade S.S glue ins fail. The only real solution seems to be Titanium glue in's. Had Petzl engineers puzzled...
16 February 2011 - 10:54pm
#14
Might be wise to learn from the experiences of others and not use stainless expansion bolts on sea cliffs, or just inland, in NZ too.
CSCC is very real, though most of the literature seems to deal with water supply systems, machinery and nuclear reactors.
Have sent an e-mail to NZAC, will be interesting to see the response, if I get one.
18 February 2011 - 1:55am
#15
This is an important thread, considering that we live in an maritime weather environment. I have an abseil carabiner which was removed from a bolted west coast climb after 10 years (Mt Drake). The bottom bend is pitted where waterdrops and icicles would accumulate.
I speculate whether replacing this alloy screwgate with a stainless Rapide would transfer galvanic corrosion into another part of the terrior bolt, hanger system. Terrior bolts were used in the 80's in Chamonix and i havent heard of any failures there, but now different bolts are used that are smaller diameter and much deeper.
Similar...yes, though probably not quite as extreme.
Sounds like it might be a good case of galvanic corrosion. Is the rust more on the hanger or the bolt? ...and if on the bolt, more on the end or closer to the hanger/nut?