似乎還沒有最適合sea cliff的bolt。Aisi 303, 304,316 都有問題！
(何中達 來自:18.104.22.168 － 中壢)
Various people have been wondering about failures of relatively new stainless bolts in sea cliffs. After a quick glance at the Rawl catalog and some quick research, I\'m not sure this surprises me.
A few people have suggested that galvanic corrosion between different grades of stainless (e.g. a hanger made from Type 316 and a bolt like the Rawl made from type 303, or its 18/8 washer) might be problematic.
303...the high sulphur content which...reduces the grade\'s...and corrosion resistance
Alternative grades to 304 should be considered in certain environments and applications, including marine conditions, environments with temperatures above 50-60C and with chlorides present
Type 316 is listed as \"standard for marine fittings\"... However, it seems that Type 316 may *also* not be appropriate for use as an anchor bolt in a sea cliff
That is, they recommend against using *either* 304 or 316 in a chloride-containing environment under tensile load (like, say, a hanging belay anchor on a popular route on a Thai sea cliff) and particularly in hot (okay, very very hot, but every bit can\'t help, and some of the stainless bolt failures heard of recently _have_ occurred in tropical, salty places) conditions. This type of stress-corrosion cracking could presumably let the shaft of a bolt
snap off without visible surface corrosion on the bolt head, washer or hanger. Ugly, huh?
The upshot? It seems to me that *all* currently-available stainless and nonstainless bolts are unsuitable for climbing anchor purposes on many (perhaps only those with porous rock?) sea cliffs.
At Acadia National Park, there are permanent toprope anchors made from glued-in 1\" stainless bar stock. It sure seemed like overkill last time I saw it, but now I\'m thinking other areas might want to consider something similar for toprope/belay anchors, unless/until stainless bolts made from appropriate materials become available.
Thor Lancelot Simon
[ This message was edited by: kevin on 2003-02-27 11:39 ]
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