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Thread: Steel alloys for hot dip galvanizing

  1. #1

    Default Steel alloys for hot dip galvanizing

    Does anyone have recommendations or suggestions for steel alloys to use for fittings that will eventually be hot dipped galvanized? Specifically for metal straps on wooden blocks and general spar hardware. After reading about it it sounds like various levels of Mn, P, Si, and carbon can affect the results of the zinc coating thickness, brittleness and even delamination tendency. Is hardening steels that will be galvanized a pointless endeavor because the will be heated again in the galvanization process?
    Thanks

  2. #2
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    Default Re: Steel alloys for hot dip galvanizing

    I do a lot of work for the commercial fishing industry. This industry uses a lot - I mean a LOT - of galvanized equipment, including block straps (not on wooden shells, but...) and uses them hard. I have never had any problems with gear that I have designed failing during normal use, nor the galvanizing failing prematurely, on equipment fabricated (cut, sheared, bent, drilled, bolted, rivetted, and welded) from plain old ASTM A-36 steel.
    Hope for the best, but plan for the worst.

  3. #3
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    Default Re: Steel alloys for hot dip galvanizing

    One minor note of caution to consider, which may not apply if you are using only mild steel for strapping, is that pre-formed shapes such as angles, can deform when hot-dipped galvanized, as the built-in stresses from the forming process are relieved by the heat.

    Don't ask me how I know this.
    Alex

    "The fishermen know that the sea is dangerous and the storm terrible, but they have never found these dangers sufficient reason for remaining ashore.
    - Vincent van Gogh

    http://www.alexzimmerman.ca

  4. #4

    Default Re: Steel alloys for hot dip galvanizing

    That’s good to know. Do they just normalize welds and/or forging afterwards and then send it in to be dipped?

    Alex,
    would normalizing the steel after working/welding it reduce any tendencies to deform or is this just an issue with high carbon alloys?
    Last edited by astevens; 06-13-2021 at 11:04 AM.

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    Default Re: Steel alloys for hot dip galvanizing

    Quote Originally Posted by astevens View Post
    That’s good to know. Do they just normalize welds and/or forging afterwards and then send it in to be dipped?
    Nope. Weld it, wire brush the welds, then toss it it the big tank of molten zinc.
    Hope for the best, but plan for the worst.

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    Default Re: Steel alloys for hot dip galvanizing

    Hey mmd,

    Does the acid bath remove the mill scale or does it need to be sandblasted ? Our "to be hot dip galvanized" pile is slowly building up.

    hardware.jpg

    Cheers,
    Mark

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    Default Re: Steel alloys for hot dip galvanizing

    My local place does really big stuff, but they have a corner for private guys and small businesses. Mill scale is OK, but paint verboten, as is rust, other than mild surface colour.
    Your stuff looks fine.
    I did a small tabernacle for a friend and dropped it in acid before he took it to the galv place. It was well under their minimum charge, but a call to them and a wink got it done in an hour, because it didn't need the pre prep phases. Cost was well under their min charge.

    Nothing to stop you dunking that lot in acid and gaining browny points..

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    Default Re: Steel alloys for hot dip galvanizing

    Mark0, we never sandblasted - nor acid dipped - anything before shipping it to the galvanized. They may have done that sort of prep, but it would have been part of their service to us. Call the galvanizer you are planning to use and ask for their guidance.
    Hope for the best, but plan for the worst.

  9. #9
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    Default Re: Steel alloys for hot dip galvanizing

    Quote Originally Posted by Mark0 View Post
    Hey mmd,

    Does the acid bath remove the mill scale or does it need to be sandblasted ? Our "to be hot dip galvanized" pile is slowly building up.

    hardware.jpg

    Cheers,
    Mark
    I do know that galvanizers cannot handle paint of any sort.
    I see some strange colours on some of those bands.
    It really is quite difficult to build an ugly wooden boat.

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  10. #10
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    Default Re: Steel alloys for hot dip galvanizing

    The flat straps are from some left over plating material, it has been blasted to remove the mill scale and the red you see is just some red oxide paint that was put on to hold while building.
    Cheers,
    Mark

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    Default Re: Steel alloys for hot dip galvanizing

    Quote Originally Posted by Mark0 View Post
    The flat straps are from some left over plating material, it has been blasted to remove the mill scale and the red you see is just some red oxide paint that was put on to hold while building.
    Cheers,
    Mark
    Well, that red oxide paint has to come off. What about the bluey green on the mast bands?
    It really is quite difficult to build an ugly wooden boat.

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  12. #12
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    Default Re: Steel alloys for hot dip galvanizing

    Quote Originally Posted by astevens View Post
    That’s good to know. Do they just normalize welds and/or forging afterwards and then send it in to be dipped?

    Alex,
    would normalizing the steel after working/welding it reduce any tendencies to deform or is this just an issue with high carbon alloys?
    I think it is only a problem with formed sections like angle, I or tubing. Flat stock like bar or plate doesn't seem to be a problem.
    Alex

    "The fishermen know that the sea is dangerous and the storm terrible, but they have never found these dangers sufficient reason for remaining ashore.
    - Vincent van Gogh

    http://www.alexzimmerman.ca

  13. #13
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    Default Re: Steel alloys for hot dip galvanizing

    Quote Originally Posted by Peerie Maa View Post
    Well, that red oxide paint has to come off. What about the bluey green on the mast bands?
    They just have mill scale. Must be the lighting / photo.

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