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Thread: Grinding Metal Near Wood Turns Black

  1. #1
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    Post Grinding Metal Near Wood Turns Black

    Hello,
    I am new to welding and working with metal and recently was grinding outside near a newly replaced cedar deck that is stained with and oil based stain. The deck is turning black and I need to clean and then re-stain the deck. I'm looking for advice on the best method to clean the black stain off the wood and then the best sealer to prevent it from happening again. Any help would be appreciated. Thanks, Milt

  2. #2
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    Re: Grinding Metal Near Wood Turns Black

    Sorry - I think I placed this in the wrong forum location and have never used these types of forums before - thanks.

  3. #3
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    Re: Grinding Metal Near Wood Turns Black

    I don't quite understand. Did the grinding sparks burn the wood? The heat may also have reacted with the tannin in the wood (cedar has a lot) causing the black if it's not physically burned. The only way I can think of preventing it in the future is to watch where you throw your sparks.... ....if that is what is the problem.

  4. #4
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    Re: Grinding Metal Near Wood Turns Black

    Two things are causing the black, grinding dust from the wheel and metal particles both hot enough to burn/melt into any non metal medium (wood, paint, epoxy).

    The steel is likely also reacting with the acids in the tannin heavy cedar (like black nail streaks).

    Depending on the amount of penetration from the grinding waste you will need to sand until it's nice, bare, clean finish or wood and refinish from new (it sucks, sorry). Any particles left will turn black and streak under a clear finish. Even with a rust inhibiting paint the acids in the cedar will pickle the metal.

    Passivization might help if you don't want to go too deep but I don't have any experience using it with wood. Maybe someone else can chime in.

    In the future a welding blanket (fiberglass tarp basically) is cheap, fast, easy, and works very well for preventing just that kind of thing.

  5. #5
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    Re: Grinding Metal Near Wood Turns Black

    Here's a tool that I use for metal. I think this will work better than a belt sander. There are a variety of sanding drums available.
    It's variable speed too.

    https://www.eastwood.com/eastwood-contour-sct.html


    Sent from my iPhone using Tapatalk

  6. #6
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    Re: Grinding Metal Near Wood Turns Black

    Pressure washer will likely take anything off the wood deck.

  7. #7
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    Re: Grinding Metal Near Wood Turns Black

    Quote Originally Posted by Milto View Post
    Hello,
    I am new to welding and working with metal and recently was grinding outside near a newly replaced cedar deck that is stained with and oil based stain. The deck is turning black and I need to clean and then re-stain the deck. I'm looking for advice on the best method to clean the black stain off the wood and then the best sealer to prevent it from happening again. Any help would be appreciated. Thanks, Milt
    The only way you are not going to ruin the finish on a wood deck from grinding metal debris is to not do it on/near the wood deck unless you cover it completely. Doesn't matter what you seal it with grinding debris will leave marks. It gets imbedded under your feet into the soft wood and/or the finish and even blowing or washing it off when your done is not going to stop it from messing it up to some degree.

    I have same problem here. Cutting and grinding outside where the asphalt was resealed recently and no matter how much you blow and wash the debris away you still get orange rust everywhere. It gets stuck in the sealer especially in our mid 90°'s weather lately.

  8. #8
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    Re: Grinding Metal Near Wood Turns Black

    Hello and thank you for the replies. I was surprised how far away the iron particles can travel. The wood is 10 foot vertical and 30 foot horizontal away from the grinding location and still turned black. The iron dust or particles must really be mobile.
    Thanks again!

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  10. #9
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    Re: Grinding Metal Near Wood Turns Black

    Wait until you grind to close to your pickup windows!

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  12. #10
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    Re: Grinding Metal Near Wood Turns Black

    Quote Originally Posted by cwby View Post
    Wait until you grind to close to your pickup windows!
    Or mirrors !!


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  14. #11
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    Re: Grinding Metal Near Wood Turns Black

    Quote Originally Posted by Lis2323 View Post
    Or mirrors !!


    Sent from my iPhone using Tapatalk
    And any type of glass, windows or doors.

    You may not see it until the sun hits it just right.


    Sent from my iPhone using Tapatalk

  15. #12
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    Re: Grinding Metal Near Wood Turns Black

    Quote Originally Posted by BD1 View Post
    And any type of glass, windows or doors.

    You may not see it until the sun hits it just right.


    Sent from my iPhone using Tapatalk
    Oh you could SEE the West Coast truck mirror I destroyed.

    Close up, far, full sun, partial light, night time, Braïlle....


    Sent from my iPhone using Tapatalk
    :

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  17. #13
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    Re: Grinding Metal Near Wood Turns Black

    Quote Originally Posted by BD1 View Post
    And any type of glass, windows or doors.

    You may not see it until the sun hits it just right.


    Sent from my iPhone using Tapatalk
    Protective glass on cell phone too.

    Sincerely,

    William McCormick
    If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.

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