Hot dipped galvanized bolts

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?
3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,230 admin
    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
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,076 ✭✭✭✭✭
    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.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • MarkCMarkC Solar Expert Posts: 212 ✭✭✭
    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??
    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
  • softdownsoftdown Solar Expert Posts: 3,592 ✭✭✭✭
    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?
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • BB.BB. Super Moderators, Administrators Posts: 32,230 admin
    And to address the treated wood fastener issue:

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

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • softdownsoftdown Solar Expert Posts: 3,592 ✭✭✭✭
    edited October 2016 #7
    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?
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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