UKC

I was reading the article on the 'new' sports crag on Gower in this month's Climb recently and having visited Rhossili beach in the past and looked at the cliffs above it, I was wondering what bolts are used? Presumably the bolts are at the very least regularly splashed by waves, but the lower ones might even get submerged at high tide?

I remember maybe a decade ago reading about how difficult Thai climbers were finding it to get bolts to stay in their crags by the sea, but perhaps that was more to do with the Limestone type? But of course pegs on sea cliffs don't seem to last very long. So how has the corrosion issue been resolved? Is a good stainless steel and resin enough?

In reply to TobyA:

In Thailand even marine grade stainless didn't last more than a year! In the end the only bolts that lasted (so far) were the titainium. They also moved to the re:500 glue which is impermeable to water. I think some of the early resins weren't actually waterproof.

Though apparently one of the big problems with Thailand wasn't so much the salt from the ocean, often the bolts look shiny outside of the rock but are totally rotten inside. I think it's something to do with rock formation. The karsts have a lot of vegetation, which has soil and catches and pools water which slowly seeps down through the rock and something about this process makes it very corrosive.

Would be interesting to know what research has been done to bolt life span on UK sea crags

In reply to TobyA:

Don't know about Gower but the bolts at Filey have a pretty hard life in soft porus rock exposed to sea spray and seepage from above. There they opted for M12 316SS rod in resin, the nuts are glued on fairly loose so the stud is not constantly in tension. It seems to work.

I guess hot forged stainless glue-ins would survive too but they're a bit short for the soft rock and expensive.

jk

In reply to TobyA:

Adrian can tell you for sure but from what I remember the higher bolts are 316L stainless and the lower ones 1.4462 Duplex stainless, that´s what I supplied.

In reply to jimtitt:

So are those basically immersion resistant? I guess ships are made of steel and seem to float around in the sea for years without too much trouble so its not that surprising. Perhaps all that discussion about pegs turning to dust under the weight of a quickdraw made me overestimate the problem.

In reply to TobyA:

It´s sort of complicated, in fact very! SCC in stainless is thought to be caused by a combination of a number of factors but in our area of interest it´s most likely that temperature and available oxygen in the chloride solution that causes the problems. Established theory said that Thailand shouldn´t have had problems with 316 but there was an unknown period of extremely low humidity at night which may be the cause. The UK is in a climatic region where the threshhold temperature in 316 is unlikely to be exceeded and the Duplex stainless steel we use (1.462) is considered to have twice the threshhold.
Just walk down to the local yacht harbour and look at all that stainless steel and most of it is "only" 304 as well. Bolt-ins have too many crevices to build up salt concentrations as well as considerable installation stress to be considered completely reliable, welded products can also have their difficulties since they become sensitised and require correct post treatment .
The bolts which are regularly immersed will be better than ones in the splash zone as they are regularly washed.

In reply to TobyA:


Generally covered in paint though (plus with sacrificial anodes to direct corrosion away from the superstructure)

In reply to TobyA:

The harbour authority here (Guernsey) have been implementing a programme of replacing all the painted steelwork round the harbour (mooring eyes, ladders, railings etc.) with stainless in recent years. I'll let you know how well it worked in 10 years or so .
Kemics is right though, Thailand limestone is very porous and sopping wet so the bolts rotted from the inside out - SS corrodes fastest in an anaerobic environment (where you can't see it ).

In reply to Toerag:

What's that?! A tide of bolts?!
Never mind,water will rust them all out eventually.

Cl SCC is the thing to be concerned about. The local temperature of the bolt can get quite high if the bolt is in direct sunlight, even in the uk, so the temperature could be reached (typically regarded as 50C). There's plenty of Cl present.

When the rod is glued in someone mentioned it's not under tension. That sounds good as the stress should be low. How are they made into the u shape? Bent? If so there might be some residual stress in the bolt which could lead to SCC.

Personally I think it would be good to use duplex if available for sea cliffs, but I've no idea how easy it is to get in the right form and how much it costs. 2205 duplex would be good I think if available in the right form at the right price.

In reply to Matt250:
They are formed (or bent for the non-techies). We start with annealed material and keep the bend radii above the minimum specified by the manufacturer but with the thicker bolts its getting difficult as this the bolt-eyes obtrusively large, one of those things I guess. The normal rule is bend radius 1.5x material diameter. Youcan check if there is any stress tearing on the bends under a microscope. A bigger problem is the stress from welding which is very localised and why we avoid welded bolts as far as possible, rings aren´t such a hassle due to their shape which takes most of the stress out.

2205 is no problem, in Europe it is designated 1.4462 and what we use as I´ve said above. It´s expensive, harder to work and previously only available in 8mm but recently 6mm has come on the market which helps with the price. It´s nice and strong though!

Lack of demand means we will probably drop it anyway when our stock runs out, many talk about better bolts but few are willing to pay for them.