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Zinc plating, what does it look like?

Discussion in 'The Garage' started by wazman, Apr 19, 2010.

  1. wazman

    wazman Been here awhile

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    I bought a pretty sweet kit of many M6 bolts with 8mm flange hex heads. Various lengths. The kind common on bikes that's hard to buy at a regular nut and bolt supplier.

    I haven't been able to find what coating is on these bolts, if any, other than they're 8.8 steel. They're silver, polished, and to my eye there's a slightly blue silver.

    Zinc?

    It's one of these Tusk Racing kits.
    #1
  2. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    Zinc plating is also known as galvanized and is silver in color. Galvi can be hot dipped or electroplated. Most "quality" nuts and bolts as in the case of say grade 8 are cad plated and is typically golden in color. From the looks of the product they appear to me to be zinc electroplated.
    #2
  3. hpsVFR

    hpsVFR Hoosier Daddy Supporter

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    I concur, but then I'm a more-or-less random guy on the internet. :lol3
    #3
  4. ggrjr

    ggrjr Been here awhile

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    Most manufacturers are going away from teh yellow color. This is due to eliminating hexavalent Chromium from the process. With the new process most of teh plating is coming out a blue silver color.
    #4
  5. the_gr8t_waldo

    the_gr8t_waldo Long timer

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    zinc looks like a slight blue tint. most hardware has this type of zinc electro plating.
    #5
  6. Beezer

    Beezer Long timer Supporter

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    I'm gonna say probably cadmium plated.... most hardware is. Cad plated bolts come in shades of bright silvery and gold colors.


    EDIT - well so there, guess I'm prolly wrong....

    http://www.boltdepot.com/metric-hex-bolts.aspx

    most the hardware I deal with is MS, NAS, and AN so the rules are different
    #6
  7. wazman

    wazman Been here awhile

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    Thanks everyone. I think they must be zinc. I believe cadmium plating is pretty much illegal these days.

    I think my bolts were originally 'cad and pas' (passivated cadmium plating I believe) and would love to have that original OEM piss-yellow colour but am happy just to have something shiny in place of tarnished brown.
    #7
  8. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    Cad plating is still very common here in the States.
    #8
  9. ggrjr

    ggrjr Been here awhile

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    It is slowly being phased out. Most manufacturers are changing their specs to remove hexavalent Chromium. I know for a fact, Cat, Deere, Linde, Textron, and EZ-Go have all gone away from it. ( They were all customers at my previous employer).
    #9
  10. Jonex

    Jonex Long timer

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    I always thought the shiny gold colored grade 8 bolts at the hardware store were some kind of zinc - they certainly don't look like the dull yellow cadmium plated AN hardware I buy from Aircraft Spruce.
    #10
  11. eepeqez

    eepeqez Long timer

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    Gold passivated zinc plated bolts are yellow.

    I worked in GM's Australian test lab back in 1993/4 and even back then GM corporate policy was no cadmium whatsoever in their products.
    #11
  12. Beezer

    Beezer Long timer Supporter

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    AN hardware is cad plated for sure... no question. So is the other U.S. aircraft standard stuff... anything that is MS or NAS.
    #12
  13. Skippii

    Skippii Milkshakes, my lad.

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    There is some confusion on the zinc/galvanized stuff. The shiny bolts you get at the store are coated with zinc.
    [​IMG]

    The bolts that are a darker, dull and rough gray color are also coated with zinc.

    [​IMG]

    Lowes calls one style "Zinc coated" and the other "Galvanized", but I can't remember which is which. The shiny ones are electroplated, and the others dipped, I think.

    Either way, don't weld on them unless you want to get poisoned.
    #13
  14. eepeqez

    eepeqez Long timer

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    The bolt above is zinc plated. It has been electroplated by immersion in a solution of zinc ions in water and applying an electric current.

    Yep, the second bolt is hot dip galvanised - it's been dipped in molten zinc, the same way they galvanise boat trailers. It has a much (~10x) thicker coating which lasts longer but doesn't lend itself to precision fasteners. Only used for things like coach bolts and coach screws for use in timber outdoors. You can often see bits of zinc adhering to the bolt.

    Most fasteners (and many parts) you see on vehicles are zinc plated and passivated. The passivation process can be coloured, commonly gold coloured. The primary purpose is to slow down corrosion of the zinc coating. The zinc corrodes preferentially to the steel, so the longer you can make it last, the longer you get before steel is corroding.

    Or grind away the zinc where you are welding and use good ventilation...
    #14