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'''The invisible weakening of stainless steel bolts'''

Sport routes allow today's climber to focus on doing moves without worrying about the consequences of a fall. His protection -- modern stainless steel
bolts -- is so strong that he can casually take multiple leader falls.
However, few climbers realize that these bolts are also susceptible to
corrosion and sudden failure. 
[[image:OoAfrica2c.jpg|right|frame|Large Stress Corrosion Cracks in the back of a stainless steel hanger that couldn't be seen until it was removed.]] 

Tropical, seaside climbing areas such as Thailand's Railae Beach and the
Carribean's Cayman Brac were among the first to experience serious accidents
due to bolt failure. What's worse, many of these injured climbers didn't
even fall. The bolts and/or hangers broke when the climber said, "Take," and
hung, and in one case in Thailand the result was a two-bolt zipper!
Everyone is familiar with oxidation corrosion, or rust, and galvanic
corrosion, that crumbly growth on their car battery. But now climbers need
to know about stress corrosion cracking (SCC) as well. SCC is like roots
growing in a crack in concrete; as they grow, they expand the crack

All three types of corrosion (which can occur simultaneously) on climbing
bolts can be caused by similar conditions. Water must be present for
oxidation, and salty water for galvanic corrosion and SCC. The longer the
metal is wet, the faster corrosion proceeds; warm temperatures accelerate
all three mechanisms. 

Salt can come from the sea but it may be in the rock itself. Granite, basalt
and other types of rock don't appear to be a problem. Porous limestone,
however, may have salt embedded within it. One theory is that rain falling
atop a limestone cliff percolates through the rock, picking up salt or other
contaminants before finding its way to the bolts.  Some climbs have only a single bad bolt where the rock seeps water.   
[[image:NutBust.jpg|right|frame|A stainless steel '''clad''' nut that crumbled due to SCC when it was removed.  The cladding can be easily seen.]] 

On tropical Cayman Brac, with its warm temperatures and sea-battered
limestone, stainless steel bolts and hangers have failed in as little as 18
months. In cooler, drier, less salty Rifle, Colorado, bolts placed in
seeping crags like the Skull Cave showed obvious corrosion after about 7
years. 

Although oxidation and galvanic corrosion can easily be seen on a bolt, SCC
is generally invisible. Not only are the cracks microscopic, SCC often
occurs behind the hanger where it can't be seen. More than one
perfect-looking bolt has snapped off under body weight. A climber on Cayman
Brac hit the deck when he weighted the second bolt of ''Throwin' the Hula
Girl.'' (I had done the route a few weeks earlier and, except for a light
patina of rust on them, the bolts looked perfect.)


SCC also attacks aluminum. A carabiner that was exposed to salt water for
about a year was tested and failed due to SCC. If you climb by the sea, wash
all your gear in fresh water once a month or when you return home.

[[image:OldNewInset.jpg|left|frame|A corroded stainless bolt and the titanium bolt that replaced it.  Notice the discoloration of the stainless steel clad stud.  Several of the bolts that looked like this broke off in our hands.  I also broke hangers in half with my fingers.]]

Needless to say, if you're bolting limestone, keep corrosion in mind. Does
the rock seep for months? Do existing bolts show any signs of corrosion? In
dry areas where there are no signs of corrosion, the least expensive option
is to use '''solid''' stainless steel bolts and hangers. Do not use stainless
'''clad''' bolts, which have a mild steel core encased in a thin layer of
stainless steel. If the cladding cracks, the bolt will fail in short order.
Stainless steel glue-in bolts are a better choice, but not in seaside rock
or seeping limestone. 

In seaside rock of any type, seeping limestone (watch for streaks or
discoloration of the rock), or where bolt or hanger corrosion is already
apparent, your only rational choice is a titanium glue-in bolt. Currently
only Ushba Mountain Works ''Now Liberty Mountaineering'' makes them, but other
manufacturers may soon offer alternatives.

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