Hot dipped galvanized bolts

MarkC · October 2016

I am using "Z" footings with IR aluminum angles to attach the IR rails to a metal roof (not a standing seam type). I have lots of galvanized 3/8" bolts/nuts/washers that can be used for these connections. Can I use these or should I "pay the price" for SS bolts/nuts?

BB. · October 2016

Here is chart that lists hot dipped galvanized steel and various materials in contact:

https://www.galvanizeit.org/hot-dip-galvanizing/how-long-does-hdg-last/in-contact-with-other-metals
http://www.bssa.org.uk/topics.php?article=89

Rural areas--not bad. In cities, the pollution can make for slight to moderate corrosion problems. Rain water is not supposed to be very bad (low conductivity). If you are near the ocean--Salt spray is always a difficult environment.

If you do use stainless bolts to SS nuts--Make sure you use some anti-seize compound. Many grades of SS will gall (threads will seize) with SS to SS contact (I have had bolts to nuts seize with just hand pressure).

After reading a bunch of different places--Hot Dip Galvanized seems to be a better material choice (aluminum and zinc are "close" electrically speaking).

In the end, using insulating paint/washers/primer/etc. between the bolts and the frame to prevent electrical connections. And I am confused/conflicted which is better.

-Bill

Dave Angelini · October 2016

On a roof? Only use the recommended material by the rail system. If anything you should call the rail manufacturer.
On the ground? Much more forgiving and easy to inspect.

MarkC · October 2016

This is a small, metal building deep in the woods! (see my avatar). The bolts will all be easily accessed by design. It is far from any salt environment - clean country air 99% of the time. Appears use of my extensive stock of hot dipped galv. is OK. I can replace them quite easily - if they can be unbolted! I used SS on the first install - think I'll check if I can unbolt them??

softdown · October 2016

BB. said:

Here is chart that lists hot dipped galvanized steel and various materials in contact:

https://www.galvanizeit.org/hot-dip-galvanizing/how-long-does-hdg-last/in-contact-with-other-metals
http://www.bssa.org.uk/topics.php?article=89

Rural areas--not bad. In cities, the pollution can make for slight to moderate corrosion problems. Rain water is not supposed to be very bad (low conductivity). If you are near the ocean--Salt spray is always a difficult environment.

If you do use stainless bolts to SS nuts--Make sure you use some anti-seize compound. Many grades of SS will gall (threads will seize) with SS to SS contact (I have had bolts to nuts seize with just hand pressure).

After reading a bunch of different places--Hot Dip Galvanized seems to be a better material choice (aluminum and zinc are "close" electrically speaking).

In the end, using insulating paint/washers/primer/etc. between the bolts and the frame to prevent electrical connections. And I am confused/conflicted which is better.

-Bill

Insulating paint/washers/primer? Thought I had most everything already. Do they micronize rubber in the paint? Plastic washers?

Treated wood can eat through galvanization I think. Depends on the level/percentage of treatment and how thick the bolts are...as I recall. Pros and cons to everything?

BB. · October 2016

And to address the treated wood fastener issue:

http://www.deckmagazine.com/design-construction/fighting-fastener-corrosion_o

-Bill

softdown · October 2016

BB. said:

And to address the treated wood fastener issue:

http://www.deckmagazine.com/design-construction/fighting-fastener-corrosion_o

-Bill

“It doesn’t matter what the pressure-treating wood company says, and it doesn’t matter what the hardware maker says. The codes all say that ‘final acceptance is up to the building official.’” Because the inspector knows more than the manufacturers? Because he/she works for the government?

Hot dipped galvanized bolts

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