Archaeometallurgy Community

  • 1.  Metal country of origin

    Posted 03-04-2021 15:46
    I have some aluminum samples (various alloys e.g. 6061, 7075, etc.) and I am trying to determine the country of origin.  Are there any ways to trace aluminum to specific ore deposits or identify it based on manufacturing processes?

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    David Sapiro
    Engineer
    King George VA
    dosapiro@gmail.com
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  • 2.  RE: Metal country of origin

    Posted 03-04-2021 16:21
    Dear David,

    Interesting question. which does not come up much in archaeometallurgy, though I have seen a paper on pre-Hall-Héroult chemically produced aluminium. In recent years I have occasionally seen fakes made of aluminium-zinc casting alloys. Sometimes these have dangerous amounts of cadmium - wash everything after sampling. I have also seen fake Chinese bronzes cast in Al alloys with enough copper so they patinate green; they did feel kind of light for a leaded bronze.

    The one time I have analysed a "proper" aluminium alloy was to determine whether a piece supposed to be by the sculptor Keith Haring was the particular alloy he regularly used. My recollection is that it probably was. 

    Given aluminium is electrolytically refined trace elements probably won't help very much, and the trace elements could have come with other additions. Stable isotope analysis will not help with aluminium itself because it only has one. Alloying additions such as magnesium and copper could help to some extent because they do have more than one isotope; copper isotopes are occasionally investigated, one example was looking to see when Michigan copper  appeared in the US copper coinage; the answer was 1837, when the mint stopped sourcing all uits copper from the UK. Lead isotope analysis might have been a better bet. However, any analysis will only tell you where the additions came from.

    My best suggestion is to build up your own database using alloys you know have been made in a particular location. Patterns might begin to emerge; also, other countries have their own standards and they might be selling an alloy as being to a particular standard when it is their own variation on it with some quirky choice of minor elements. I don't think there are any short cuts for this one.

    Regards,
    Peter

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    Peter Northover
    Retired
    University of Oxford
    +44 1865 820543
    peter.northover@retired.ox.ac.uk
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  • 3.  RE: Metal country of origin

    Posted 03-05-2021 09:51

    Peter,

    Isotope analysis of the alloying elements is a good idea.  What sort of instrumentation is required for that?  I know I don't have access to that instrumentation, but I might be able to find another lab within my organization that does.

    I will look at the standards of the suspected countries of origin.  This is certainly an easier solution, as long as their specs are different enough to notice.



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    David Sapiro
    Engineer
    King George VA
    dosapiro@gmail.com
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  • 4.  RE: Metal country of origin

    Posted 03-04-2021 18:11
    Hi David,
    These alloys are elaborated in order to have a chemistry that is conforming to industry standards. The designations (6XXX or 7XXXX) are linked to this. 
    Only trace elements could retrace to the ore but only if we have informations on the specifics of all ores in the world. I am not even sure if this information is available.
    If you are looking for the alloy temper condition (T6, T73, etc...), hardness and electrical conductivity are indications. Microstructure could help but since the difference is in tiny phases, you need SEM and in some instance even TEM.
    Macros could give you info on the thermo-mechanical processing (drawing, stretching, ...), and is achievable by optical microscopy.
    Hope this help.
    Best,
    Nihad


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    Nihad Ben Salah
    President
    NBS- M&P Consulting
    Canada
    https://www.nbsmpconsult.com/en/home
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  • 5.  RE: Metal country of origin

    Posted 03-05-2021 09:53

    Nihad,

    I was thinking the same thing, and I am willing to tell my customer that it cannot be done.  Thanks for your input!



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    David Sapiro
    Engineer
    King George VA
    dosapiro@gmail.com
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  • 6.  RE: Metal country of origin

    Metro NY/NJ Chptr Admin
    Posted 03-05-2021 11:56
    A number of years ago I tired doing this for a different alloy from the aluminums. It was a bronze alloy from about 2000 years ago. In my case the question was being asked of authenticity. 

    Both Peter Northover and Nihad Ben Salah have given you quite good answers. I used to work with a chemist that did the analysis for ferrous based alloys and he had a data base of all the trace elements from numerous sources and could pin-point where a particular ferrous alloy was produced, pretty much world wide. But that was due to having decades of data from known sources. Additionally, it only included modern sources. You are looking at aluminums, so those are not particularly old, but you would indeed need an extensive database that would take quite some time to build. The other problem with this alloy system, is that  given the way the ores are shipped from mine to mill, you might not have such good luck in todays commercial environment.

    Good luck to you and for sure let us know how you get on.

    dj

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    David Jones
    Senior Principal Materials Engineer
    Stryker Orthopeadics
    Mahwah NJ
    (914) 469-2958
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  • 7.  RE: Metal country of origin

    Posted 03-05-2021 15:27

    Hi David:

     

    Not to complicate things further but there may be an additional difficulty in identifying the country of origin of aluminum components:  In some cases, the country of origin of the ore may not be the same as the country of production of aluminum metal.  E.g., for a long time Greek bauxite was converted to alumina, which was subsequently shipped to a different country in Europe to electrolytically produce aluminum.  I do not know how prevalent this practice is today, but depending on the age of your parts or artifacts that may be a concern.

     

    Nassos