Not much force with a ratchet snapped these heads - how dangerous are they.

While rebolting a route I ran into a couple of these fairly corroded wedge bolts. It took very little force to snap the head off with a 1/4 turn of a 12" ratchet. The bolts are 3/8"

Any idea how dangerous these would be? Force generated by a ratchet probably isn't really comparable to falling, but the only other time I've snapped a bolt was with a breaker bar, and it took a whole lot of force. If I was thinking, I would have tried the funkness on them after the first one snapped so easily.

Luckily I don't think I've seen these on any of the other routes around.

Only way to gather a vague understanding of the safety these would provide a climber would be to pull test them. You could use a load cell and do some controlled drops on a sample of bolts that look similar to these at the same area.

Visual inspection rarely provides you information. i.e. old 1/4” rusty button heads can often still be extremely strong in dry/non corrosive environments with hard stone.

So - we are often just replacing when the community feels doubt in the margin of safety provided by the hardware. Once you begin, as you learned, some truths are revealed!! 

I'd reckon not very dangerous just sitting on the table. 

It looks like you "sheared" them, 3/8" wedges can shear at a fairly low torque. The nut looks seized to the stud, next time you might consider using some Kroil Lubricrant or giving them a good soak in PB Blaster for awhile before working if your goal is to remove the entire bolt and reuse the hole. I'm not sure that you can make much of an extrapolation between the torque it takes to shear the bolt and the ultimate pull-out/shear strength. it's an entirely different force put on the bolt. Imagine trying to pull a rod of steel apart lengthwise, vs twisting it until it shears, you could likely twist it apart with little effort but it will take enormous force to pull it apart lengthwise. Nonetheless those look like they were due for replacement, hopefully you're replacing them with a high quality/long lasting solution. Thanks for getting out there and doing the work. 

That looks like a mixed metal install. Those metolous hangers are stainless and bolts are non-stainless steel.  Yes they are dangerous.  Someone put in a bunch of that here too. 

climber pat wrote:

That looks like a mixed metal install. Those metolous hangers are stainless and bolts are non-stainless steel.  Yes they are dangerous.  Someone put in a bunch of that here too. 

A bit of a thread drift... 

I think we can all agree galvanic corrosion is a well known phenomenon exacerbated by certain environments, materials, and circumstances. Most people will also agree that Stainless or Titanium is the preferred solution for any long term outdoor install. In certain environments the effect of galvanic corrosion is very pronounced, for example a stainless hulled boat (large surface area) with zinc plated carbon steel fasteners (small amount of material to attack) sitting in an electrolyte solution (i.e. the ocean), especially in warmer climates where the reactions take place faster. 

My question is, in what environments have people noticed this to make a considerable difference in the rate of corrosion for climbing bolts, when comparing mixed metal combos to all plated hanger/bolt combo. Has this actually been an issue in your area in particular? Or would the corrosion have been an issue given the age and environment of the bolt regardless of the combo? 

My experience in our locale has been: We have around 20,000 bolts locally that were installed with mixed metals (SS hangers and plated bolts). For a short period of time, after mixed metals was proposed as an issue for climbing bolts, but before most people around here started using all SS, people made the switch to using plated hangers paired with plated bolts. In replacing 800 or so bolts here, with both combinations, I haven't noticed much of difference in rate of corrosion related to mixed metal vs. all plated. 

Anecdotally out of those 20,000, we've never had a bolt fail during a fall that's been attributed to corrosion. These are mostly 1/2" rawls, so plenty beefy and we do have fairly active stewardship, it's inland so no sea water corrosion, and most of the bolts aren't older than the early 90's.

Regardless of the bolt/hanger combo used, the bigger factors I've seen in how corroded bolts are has been the sun aspect (how quick does the cliff dry out after precip), if it's in a water streak, and the mineral content of the rock (we have a few cliffs with a high salt content).  

The only difference I've seen is that people freak out when they see the rusty hangers from the all plated installs, so we get lots of bolt reports from that, while the mixed metal bolts installed at the same time on the route next door folks see as perfectly safe. In many cases both bolts exhibit the same mild surface corrosion and are plenty safe/strong still. 

DrRockso RRG wrote:

A bit of a thread drift... 

I think we can all agree galvanic corrosion is a well known phenomenon exacerbated by certain environments, materials, and circumstances. Most people will also agree that Stainless or Titanium is the preferred solution for any long term outdoor install. In certain environments the effect of galvanic corrosion is very pronounced, for example a stainless hulled boat (large surface area) with zinc plated carbon steel fasteners (small amount of material to attack) sitting in an electrolyte solution (i.e. the ocean), especially in warmer climates where the reactions take place faster. 

My question is, in what environments have people noticed this to make a considerable difference in the rate of corrosion for climbing bolts, when comparing mixed metal combos to all plated hanger/bolt combo. Has this actually been an issue in your area in particular? Or would the corrosion have been an issue given the age and environment of the bolt regardless of the combo? 

My experience in our locale has been: We have around 20,000 bolts locally that were installed with mixed metals (SS hangers and plated bolts). For a short period of time, after mixed metals was proposed as an issue for climbing bolts, but before most people around here started using all SS, people made the switch to using plated hangers paired with plated bolts. In replacing 800 or so bolts here, with both combinations, I haven't noticed much of difference in rate of corrosion related to mixed metal vs. all plated. 

Anecdotally out of those 20,000, we've never had a bolt fail during a fall that's been attributed to corrosion. These are mostly 1/2" rawls, so plenty beefy and we do have fairly active stewardship, it's inland so no sea water corrosion, and most of the bolts aren't older than the early 90's.

Regardless of the bolt/hanger combo used, the bigger factors I've seen in how corroded bolts are has been the sun aspect (how quick does the cliff dry out after precip), if it's in a water streak, and the mineral content of the rock (we have a few cliffs with a high salt content).  

The only difference I've seen is that people freak out when they see the rusty hangers from the all plated installs, so we get lots of bolt reports from that, while the mixed metal bolts installed at the same time on the route next door folks see as perfectly safe. In many cases both bolts exhibit the same mild surface corrosion and are plenty safe/strong still. 

Looking at the picture the hanger is in good shape, the bolt is very corroded.  That's a problem.  The install would have been better if both the bolt and the hanger were non-stainless.  

Like the OP, I had a similar install break at very very low torque when trying to remove it.  I would guess way less than 1 ft.-lb.

Like you we have many old 1/4 inch button heads from the 1970s that are very difficult to remove.

All the mixed metal installs I have replaced have seriously corroded bolts.  Equivalent aged non-stainless installs are still in good shape as are the stainless installs, of course 

Mixing the metal types is a big no no.  It would be better if the bolt was stainless and the hanger non-stainless then at least you could inspect the sacrificial part.

I live in the desert of southern NM

I've experienced this as well.  Older wedge bolts that seemed to have a lot of metal left to them would shear very easily when trying to spin them:

https://www.mountainproject.com/forum/topic/122017874/preventing-old-bolts-shearing-off

DrRockso RRG wrote:

A bit of a thread drift... 

I think we can all agree galvanic corrosion is a well known phenomenon exacerbated by certain environments, materials, and circumstances. Most people will also agree that Stainless or Titanium is the preferred solution for any long term outdoor install. In certain environments the effect of galvanic corrosion is very pronounced, for example a stainless hulled boat (large surface area) with zinc plated carbon steel fasteners (small amount of material to attack) sitting in an electrolyte solution (i.e. the ocean), especially in warmer climates where the reactions take place faster. 

My question is, in what environments have people noticed this to make a considerable difference in the rate of corrosion for climbing bolts, when comparing mixed metal combos to all plated hanger/bolt combo. Has this actually been an issue in your area in particular? Or would the corrosion have been an issue given the age and environment of the bolt regardless of the combo? 

My experience in our locale has been: We have around 20,000 bolts locally that were installed with mixed metals (SS hangers and plated bolts). For a short period of time, after mixed metals was proposed as an issue for climbing bolts, but before most people around here started using all SS, people made the switch to using plated hangers paired with plated bolts. In replacing 800 or so bolts here, with both combinations, I haven't noticed much of difference in rate of corrosion related to mixed metal vs. all plated. 

Anecdotally out of those 20,000, we've never had a bolt fail during a fall that's been attributed to corrosion. These are mostly 1/2" rawls, so plenty beefy and we do have fairly active stewardship, it's inland so no sea water corrosion, and most of the bolts aren't older than the early 90's.

Regardless of the bolt/hanger combo used, the bigger factors I've seen in how corroded bolts are has been the sun aspect (how quick does the cliff dry out after precip), if it's in a water streak, and the mineral content of the rock (we have a few cliffs with a high salt content).  

The only difference I've seen is that people freak out when they see the rusty hangers from the all plated installs, so we get lots of bolt reports from that, while the mixed metal bolts installed at the same time on the route next door folks see as perfectly safe. In many cases both bolts exhibit the same mild surface corrosion and are plenty safe/strong still. 

Are the bolts that you're referring to typically in overhung, "dry" placements? How much corrosion is visibly evident on these. Like subsequent posters above, I've encountered mixed metal placements that broke under mere rope tension, or with very little torque applied with a wrench or puller. These were all in AZ in our incredibly arid climate, BUT were in areas of low angle slab runoff that received plenty of moisture when it did rain. Other mixed metal placements in different settings were bomber. 

DrRockso in my many years of replacing hardware in NC and WV The bigger factor in plated bolt condition is rock type. Bolts in sand stone dont hold up as well as bolts in granite and quartzite. Bolts that get wet from the inside of the hole  oxidize more quickly regardless of the hanger type. That is still no justification for plated steel. Mixed metal does seem to make the nut or head of the bolt rust quickly. 

Good thing that even in somewhat damp sandstone 30+ year old 304 SS seems to be working!

Andy Bennett wrote:

Are the bolts that you're referring to typically in overhung, "dry" placements? How much corrosion is visibly evident on these. Like subsequent posters above, I've encountered mixed metal placements that broke under mere rope tension, or with very little torque applied with a wrench or puller. These were all in AZ in our incredibly arid climate, BUT were in areas of low angle slab runoff that received plenty of moisture when it did rain. Other mixed metal placements in different settings were bomber. 

Actually primarily the opposite, the slabs here tend to dry out fairly quickly after a rain while overhung areas tend to stay more manky and due to the pourous nature of the rock and can suffer from seep seasonally, especially in the winter from snow melt, so the inside of the hole can remain wet for long periods of time. On the other hand, overhung areas that don't suffer from seep and have a good sun aspect can have bolts that look brand new 20 years later, similarly for slab routes which have good sun aspect. With the humidity here in the Southeast certain times of the year, condensation can be a big factor too, so areas that get less airflow tend to be more mank. Of course bolts on slabs with consistent water runoff still corrode quickly, all this to say that overhanging vs slab doesn't seem to be a defining factor here.  

Do you have similar all plated placements from the same era nearby to be able to make a good comparison? Perhaps the rock type is partially to blame? Besides the few salty walls here that I mentioned earlier, our sandstone tends to be pretty chemically inert, whereas I've seen limestone areas that can be quite corrosive. 

DrRockso RRG wrote:

Actually primarily the opposite, the slabs here tend to dry out fairly quickly after a rain while overhung areas tend to stay more manky and due to the pourous nature of the rock and can suffer from seep seasonally, especially in the winter from snow melt, so the inside of the hole can remain wet for long periods of time. On the other hand, overhung areas that don't suffer from seep and have a good sun aspect can have bolts that look brand new 20 years later, similarly for slab routes which have good sun aspect. With the humidity here in the Southeast certain times of the year, condensation can be a big factor too, so areas that get less airflow tend to be more mank. Of course bolts on slabs with consistent water runoff still corrode quickly, all this to say that overhanging vs slab doesn't seem to be a defining factor here.  

Do you have similar all plated placements from the same era nearby to be able to make a good comparison? Perhaps the rock type is partially to blame? Besides the few salty walls here that I mentioned earlier, our sandstone tends to be pretty chemically inert, whereas I've seen limestone areas that can be quite corrosive. 

These were mainly 3/8" plated splitshafts with either Metolius or SMC SS hangers. 3/8" plated wedges here seem to be fine no matter the hanger metal or placement environment. Granite/granitic gneiss

Two points to note a) the original diameter is considerably reduced by corrosion via pits/cracks, and b) the fracture surface is typical of brittle fracture. I'd judge that any such bolts in this location, and of this age, are hopelessly compromised.

There was a time when I was reasonably relaxed about galvanic corrosion between mismatched anchor components comprised of stainless steel and plated carbon steel. My theory was that there would be no hidden surprises, and inspection was a good enough safeguard. It is interesting that a quick survey of the literature turns up a mix of papers some "proving" it cannot be a problem while others assert it is a big deal. Yet I have no trouble pointing to accelerated corrosion both in situations of plated hangers and chain sets on stainless steel bolts and vice versa.

My problem is that I have spent too many years working on the hydrogen embrittlement problems that attend attack by sulphate reducing bacteria (SRB). Trivial snapping of a bolt is the hallmark of this problem that affects Railay/Tonsai, Long Dong, the Costa Blanca and Portugal. I'm not suggesting we have an SRB problem here, but we do have a significant galvanic potential that is well and truly sufficient to generate hydrogen at the cathode. It makes me nervous.

In theory, the stainless steel is the cathode and the carbon-steel is the anode. Thus we get rapid anodic attack of the plated steel, which we see, but can only suspect that hydrogen will be released at the stainless hanger. So any embrittlement should be at the hanger not the bolt. However, we need to play into this the fact that the steel is zinc plated, and thus would be the ultimate anode until it was all consumed. You don't need to dig far to find reports of hydrogen embrittlement of plated steel under certain aggressive corrosive conditions. Without taking a look at the microstructure I can't be sure we are seeing hydrogen embrittlement of the steel, but with high galvanic currents flowing, as must be the case given the observed corrosion, an equivalent volume of hydrogen is being produced somewhere on a metal surface. Depending upon the chemical environment, and the presence of even trace amounts of catalytic poisons such as sulphide, hydrogen embrittlement is a real possibility.

If we have a situation whereby galvanic corrosion can sponsor hydrogen embrittlement, there is no way casual observation will alert a climber to a dangerously weakened bolt.