Bolting: Mixing Metals

I was wondering if anyone knows the deal with mixing metals between bolts and hangers. Fixe's website advises to not mix different grades of steel due to possible promotion of deterioration. This brings my question: is mixing carbon steel powers bolts with stainless steel hangers a bad combination? or is it safer to throw out the extra $5 and get the stainless bolts?

Zach B wrote:I was wondering if anyone knows the deal with mixing metals between bolts and hangers. Fixe's website advises to not mix different grades of steel due to possible promotion of deterioration. This brings my question: is mixing carbon steel powers bolts with stainless steel hangers a bad combination? or is it safer to throw out the extra $5 and get the stainless bolts?

Galvanic corrosion. The carbon steel will be the anode, ie, it would get consumed first if galvanic corrosion happens. If.

Probably not as big a deal where its really, really, dry (like, say, the interior of the U.S. in the western desert areas). Back east, with all the humidity and moisture? Might be a problem.

Yeah, safer to not mix metal. Hard to quantify, though.

I think it's a good questions and definitely worth discussing. I know of at least two bolts which failed as a result of Galvanic Corrosion, see link below. I definitely think it is worth spending the extra cash and doing it right the first time. I would recommend following the manufacturer's instructions as well as do your own research into the 'correct' way to install an anchor (I've attached 2 links which I have found helpful).

hope this helps!

cascadeclimbers.com/forum/u…

safeclimbing.org/education.htm

bolt-products.com/Glue-inBo…

smoothD wrote:I think it's a good questions and definitely worth discussing. I know of at least two bolts which failed as a result of Galvanic Corrosion, see link below. I definitely think it is worth spending the extra cash and doing it right the first time. I would recommend following the manufacturer's instructions as well as do your own research into the 'correct' way to install an anchor (I've attached 2 links which I have found helpful). hope this helps! cascadeclimbers.com/forum/u… safeclimbing.org/education.htm bolt-products.com/Glue-inBo…

One thing of note is that the failed bolts mentioned above were aluminum hangers on galvanized bolts. Aluminum will suffer from galvanic corrosion (when paired with steel) much more quickly than steel with stainless steel. I'm not saying that you should go ahead and mix metals, but in a dry arid climate, a galvanized bolt with a stainless hanger will last many, many years. That being said, it is still always a good idea to use only stainless hardware. Stainless hardware will last much longer but does cost more.

kennoyce wrote:...but in a dry arid climate, a galvanized bolt with a stainless hanger will last many, many years...

IMO it would be better to use a stainless bolt and a galvanized hanger (if you feel the need to mix metals).
This way the hanger will corrode first and you can inspect and change it contrary to the bolt in its hole.

Thanks for the info!