Galvanic corrosion question.

So I was reading the bolts bolts bolts thread and want to hopefully get some clarification.

My current system for bolts is this: Powers 3/8"x3" 303/304 SS bolts with either Fixe plated steel hangers or Metolius SS hangers. then quicklinks (SS or plated depending on what I had on hand) and then chain (not SS) or hooks (again not SS)

I am using this set up here in southern Arizona where during the summer we have a 2-3 month monsoon season where it rains anywhere from 1-7x per week (but the heat dries things up by the next day) and then we will have maybe 5-10 rainy days over the winter/spring. so not a lot but some rain.

I am aware that mixing a SS bolt with a plated steel hanger can cause galvanic corrosion. My question is where will this corrosion occur? Will it be on the plated steel hanger? the SS bolt? Both? The quick link (assuming its not SS) ect... Basically will the corrosion be limited to the non-SS components?

Am I better off using plated steel/non-SS bolts with the plated steel hangers?

I ask because the discussion in the bolts bolts bolts thread is based on SS hangers on plated steel bolts and obviously having a bolt rust (potentally out of sight) is much more dangerous and harder to fix (replace) than having a hanger eventually rust.

Thanks,
Nick

Disclamer: I have almost used up my batch of 100 Fixe plated hangers and will be getting SS in the future so the info gained from this thread will affect IF and how high a priority I place on replacing the non-SS hangers with SS. Going forward the extra $30-50 per 100 hangers is worth the peace of mind of knowing I wont have to replace them in my lifetime (and the time involved).

Easy answer, since you're already doing the right thing and using SS bolts, just go SS hangers and have peace of mind.

NickMartel wrote:So I was reading the bolts bolts bolts thread and want to hopefully get some clarification. My current system for bolts is this: Powers 3/8"x3" 303/304 SS bolts with either Fixe plated steel hangers or Metolius SS hangers. then quicklinks (SS or plated depending on what I had on hand) and then chain (not SS) or hooks (again not SS) I am using this set up here in southern Arizona where during the summer we have a 2-3 month monsoon season where it rains anywhere from 1-7x per week (but the heat dries things up by the next day) and then we will have maybe 5-10 rainy days over the winter/spring. so not a lot but some rain. I am aware that mixing a SS bolt with a plated steel hanger can cause galvanic corrosion. My question is where will this corrosion occur? Will it be on the plated steel hanger? the SS bolt? Both? The quick link (assuming its not SS) ect... Basically will the corrosion be limited to the non-SS components? Am I better off using plated steel/non-SS bolts with the plated steel hangers? I ask because the discussion in the bolts bolts bolts thread is based on SS hangers on plated steel bolts and obviously having a bolt rust (potentally out of sight) is much more dangerous and harder to fix (replace) than having a hanger eventually rust. Thanks, Nick Disclamer: I have almost used up my batch of 100 Fixe plated hangers and will be getting SS in the future so the info gained from this thread will affect IF and how high a priority I place on replacing the non-SS hangers with SS. Going forward the extra $30-50 per 100 hangers is worth the peace of mind of knowing I wont have to replace them in my lifetime (and the time involved).

The corrosion would mostly occur on the plated steel components. The SS components would not be affected as much. The reason why galvanic corrosion most often occurs on the bolt is because there are not many manufacturers that sell products in the USA that make plated steel hangers. So, most of the hangers on sport routes in the USA are stainless. However, people get cheap and get plated steel bolts, which is what causes these problems.

Quite simply, stop mucking around and go the glue-in u-bolt. Done once and there for ages. I'm in Australia and in my experience any new bolting or rebolting that is done is either ring or ubolts. The expansion bolts are viewed as old school.

The galvanic corrosion will occur on your plated steel components. Here we use regular (non-ss) maillons and chains on some of our anchor and replace them every 5-10 years. The bolt and hanger are ss and still looks brand new after 10 years aside from a little surface rust from the maillon. So you may have to change your plated ste hanger in a ehile but the bolt should remain good for much longer As for expansion bolts, they may be viewed as old school in the land down under but they're still modern on any hard rock such as granite or diabase. From what I've gathered aussie crags have super soft sandstone.

I am climbing/bolting in a hard rock area so I have never even seen a glue in on a route as everyone here uses wedge bolts (granite/gneiss).

I'm told its really not much of a worry unless you are in a wet area... a really wet area.

Sam Lightner, Jr. wrote:I'm told its really not much of a worry unless you are in a wet area... a really wet area.

I have seen galvanic corrosion occur in Red Rocks. I am not sure that Red Rocks constitutes a really wet area, after all it is the desert. But yes, the issue will be amplified if you are bolting in a really wet area.

i've seen it in several places in CO and CA. Several times it appeared that somebody had replaced cold shuts with new hangers, which is good, but that the new hangers were stainless and the old bolts/washers/nuts were carbon.

Do the climbing world a favor and never use dissimilar metals. (Always match metals - stainless with stainless, galvanized with galvanized). One of the principal problems with corrosion is that it's very difficult to gauge when a real problem is occurring prior to failure, especially when the effected metallurgy is not visible; such as the case of a stainless hanger / carbon steel bolt combo. One can sometimes see corrosion, but it's very difficult to know what is "safe" without some extensive study. Obviously, the original poster suggested the opposite, but the cost differential is not worth the potential problem.

Just so there is no confusion, the problem occurs on the less noble metal (in this case the plated steel). en.wikipedia.org/wiki/Galva…
The Galvanic effect is a function of the exposed surface area of each metal. When the ratio of noble metal surface area to less noble surface area is high - a big problem exists. When the opposite is true, the problem is not as pronounced. I'll leave it at that, but there are a number of additionally complicating circumstances. Bottom line - don't do it.

Another (under-appreciated) consideration is crevice corrosion in the bolt hole, exacerbated by a galvanic effect. en.wikipedia.org/wiki/Crevi…

I'm a materials engineer.

and, to add to that. if you do use anything plated make sure the plating is consistent.

powers are zinc coated, so use zinc coated hangers ect.