Galvanic issues?

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mgookin said:
We use hot dipped zinc bolts to build docks over salt water. As the tide rises and falls, the bolts are under water and out of the water. That's what I call exposed to the elements. Not sure if I read a previous post in the intended context.
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+1 on its use. i am just noting, given that zinc plays better with Al than SS does, and SS is ~2.5x more $$, to me a zinc item is a better choice. but as i noted, if the installer is not the owner of legal docs then just go with whatever is prescribed, can always argue the cause for future jobs as needed, etc.

if its a 50yr item that is described in the legal docs, i would use a coating under the lug, zinc hardware, proper locktite, and torque wrench. the copper wire (is it Cu?) & burndy will be dust long before there is a issue with bolt and Al.
 
FionaZuppa said:
read about zinc use till your eyes burn
http://www.galvanizeit.org/sustaina...galvanizing/what-is-zinc/zinc-in-construction

http://www.finishing.com/421/40.shtml
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Nothing in there says that zinc plated hardware is suitable for outdoor installations, dichromate or not. There's a huge difference between plated and hot-dipped galvanized. You've got to consider whether the hardware will rust regardless of galvanic issues, after all.

SS is ok, not as good as zinc to Al on the chart, and SS costs a lot more.
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Again, show me where I can get a galvanized #10 starwasher. A #10 starwasher also doesn't cost much regardless of what it's made out of.

post #17 ???? post #12 says 3/8" bolt, so where does #10 come into this? $$ for 3/8" SS bolt vs 3/8" hot zinc, is a big diff. SS is about 2.5x more $$.
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Post 12 is not my post and you were responding to my post #7 in your post #8, which was before any sizes were mentioned. Try to follow the conversation.

Where hot dipped galvanized is available for the part size I'm sure it works fine but it sure is interesting that the $18 billion a year industry has decided that SS is standard practice for fasting aluminum together on a daily basis.
 
jaggedben said:
Where hot dipped galvanized is available for the part size I'm sure it works fine but it sure is interesting that the $18 billion a year industry has decided that SS is standard practice for fasting aluminum together on a daily basis.
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perhaps for small hardware less than 1/4", but 1/4" and above hot dipped should be able to do the job. but to note, with zinc coatings it all depends on the coating thickness and type.

i would say SS has its place, but for a majority of the SS that is used for attaching Al in solar industry i am willing to bet zinc-cobalt would last a lifetime. closer to sea water i would be onboard with SS.

for the OP, i myself still stand in the zinc camp, zinc-cobalt/zinc-dichromate or hot dipped, up in 3/8" bolt, i would lean on hot dipped. if the argument is in that "10yr parts/materials warranty" area, and you had just a few of these to do, then go SS because it looks better.

but then again, i think the OP dilemma is, how to convince someone else to change the spec from bronze to XYZ. if OP wanted to convince me of a change i would side with the hot dipped hardware (unless looking pretty was a major factor), etc.

zinc coated hardware is used extensively in various industries where the applications are in or exposed to sea water. surely if there was a need for the more $$ SS there they would adopt it?
 
mgookin said:
We use hot dipped zinc bolts to build docks over salt water. As the tide rises and falls, the bolts are under water and out of the water. That's what I call exposed to the elements. Not sure if I read a previous post in the intended context.
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If your zinc coated bolts are just in contact with wood, then you have no galvanic issue.
 
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