Toning is corrosion!

Discussion in 'Coin Chat' started by TypeCoin971793, Jul 8, 2018.

  1. Kentucky

    Kentucky Supporter! Supporter

    You're old enough to remember that old commercial where they wrap an onion in "regular" plastic wrap and in Saran (back when Saran was saran) Wrap and they can't smell the onion. That's why I mentioned it.
     
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  3. Kentucky

    Kentucky Supporter! Supporter

    I bought some at a Japanese Supermarket and was thinking of trying to heat seal some.
     
  4. -jeffB

    -jeffB Greshams LEO Supporter

    It seems like I saw a lab supply catalog sometime in the last ten years that listed it. Of course, it was priced as a lab supply ($$$), but it's apparently still available, just not as a mass-market item.

    By "Japanese Supermarket", do you mean a supermarket in Japan, or something in the US that caters to Japanese?
     
  5. Seniorchief

    Seniorchief New Member

    Thanks for that input, gentlemen. Very informative. So, as a start, I purchased a couple boxes of dollar coin snaps made by BCW. However, I'm concerned that they're made in China and have foam inserts. I generally don't trust things made over there even if they supposedly have "quality control", I get concerned about the raw materials used to construct them. Any opinions or other recommendations? I sure appreciate this forum; I've learned a lot, just remembering the info gets to be a challenge. I've discovered that growing old is not for pansies!
     
  6. Oldhoopster

    Oldhoopster Member of the ANA since 1982

    Someone once said, "Youth is wasted on the young". ;)
     
  7. V. Kurt Bellman

    V. Kurt Bellman Yes, I'm blunt! Get over your "feeeeelings".

    You're right to be suspicious of BCW. The outer shell should be fine, but I'm skeptical of the foam.
     
  8. John Skelton

    John Skelton Morgan man!

    Hey, don't mess with us GMO people! My parents did what they had to do to bring me into this world!
     
  9. John Skelton

    John Skelton Morgan man!

    C'mon now, leave Toto out of this!
     
    Gregg likes this.
  10. RICHARD K

    RICHARD K MISTY & SASHA

    I believe they use electrolysis, somehow with water and 9 volt battery . I think on you-tube they have some experiments to look at.
     
  11. GDJMSP

    GDJMSP Numismatist Moderator

    What many don't stop to think about are that there are great many other variables involved besides geographical location that determine if, how, and why coins tone. And those other variables often have a much greater impact.
     
  12. V. Kurt Bellman

    V. Kurt Bellman Yes, I'm blunt! Get over your "feeeeelings".

    You know what I WISH I could see? A brand spanking new .999 silver coin that has spent about a month near Kilauea.
     
    Kentucky and juris klavins like this.
  13. GDJMSP

    GDJMSP Numismatist Moderator

    Well, we have several members who live in Hawaii, perhaps one of them will see this and post one for you :)
     
    Kentucky likes this.
  14. Scuba4fun777

    Scuba4fun777 Well-Known Member

    However, the ultimate goal of both is the same - to keep 2 different environments separate. In both cases, a failure is a failure - whether it happens over a few seconds or a few decades. The difference is the severity of the results of the failure.
     
  15. Kentucky

    Kentucky Supporter! Supporter

    I somehow
    I somehow grow less concerned about what happens after I die.
     
    V. Kurt Bellman likes this.
  16. V. Kurt Bellman

    V. Kurt Bellman Yes, I'm blunt! Get over your "feeeeelings".

    “We are stardust, we are golden, we are billion year old carbon,
    And we got to get ourselves back to the garden.”
     
    Kentucky likes this.
  17. Kentucky

    Kentucky Supporter! Supporter

    [​IMG]

    West LA

    [​IMG]

    Polyvinylidine chloride
     
    -jeffB likes this.
  18. -jeffB

    -jeffB Greshams LEO Supporter

    Hmmmm.

    Added to my "Asian mega-market" shopping list...
     
    Kentucky likes this.
  19. -jeffB

    -jeffB Greshams LEO Supporter

    Hah! I just found the stuff on Amazon Prime for $10.99:

    https://www.amazon.com/Regular-Plas...0012VQLKY/ref=cm_cr_arp_d_pl_foot_top?ie=UTF8

    First time I ran the label through Google Translate it said "polyvinyl chloride", but the second time through it did say "polyvinylidene chloride", and the temperature range checks out. It does say "fatty acid derivatives" added as a softening agent, so I'm not 100% sure about putting it in contact with a coin, but I'd expect wrapping an Air-Tite (or a whole album) in it would put the brakes on oxygen diffusion in a big way.
     
    Kentucky likes this.
  20. NSP

    NSP Well-Known Member

    This is a follow-up to the post I made several months ago following the completion of my High Temperature Corrosion class. As I suspected, everything changes when heat is involved. I will do my best to explain it in a way that makes it somewhat clear. Before I begin, I need to provide some background information.

    When the coins you tested sat out in open air for many years, they developed corrosion products on their surfaces, like Ag2S, Ag2O, etc. These corrosion products are ionic compounds and on average have a regular crystalline structure. They are not perfect, however. Atoms can be missing (“vacancies”), atoms can be sitting in places out of the regular crystalline structure in gaps where they shouldn’t be (“interstitials”), etc. All of these anomalies are referred to as “defects” in the corrosion products.

    Atoms can migrate through the corrosion product layer via these defects. The interstitials can move around, and vacancies can swap positions with atoms and effectively move around. At high temperature, defects are able to move a lot more freely because they have more energy to do so. More mobile defects means reactants for the corrosion reaction can move more freely. This means oxidation can occur more rapidly. To summarize, high temperature = reactants can move through the corrosion product layer more easily = more oxidation.

    When exposed to a high temperature oxygen atmosphere, most metals will end up forming a scale that slows down further oxidation. Everything changes when sulfur is involved. I believe that at 350 °F oxygen and sulfur would react to form species like SO2 and SO3. Both sulfur oxides are not nice to metals or their protective scale of oxidation products. In the presence of sulfur oxides, metal oxides and metal sulfides simultaneously form at a fast rate. The sulfides and oxides do not provide any protection after they form and are full of defects. It is thought that sulfur oxides can permeate through defects in the corrosion products, meaning that corrosion occurs deeper and deeper into the metal. This is why your coins didn’t stand a chance despite the presence of Ag2S, Ag2O, etc. on their surfaces: the sulfur oxide goes right through the corrosion products and destroys everything in its path.

    The effect would be even worse at higher temperatures… 350 °F isn’t terribly hot. At lower temperatures, the coins probably wouldn’t be so destroyed. At room temperature, this likely wouldn’t happen at all because sulfur oxides would not form as readily as they do at high temperatures and the defects would not allow for much movement of sulfur oxides.

    It is worth noting that the mechanism I described here is the current understanding of how this occurs... that understanding could change in the future.

    I suppose this begs the question about how people can successfully artificially tone their coins in an oven without destroying them. If I had to guess, they probably don’t use a pile of pure sulfur because the resulting cloud of warm SO2 gas would not be beneficial to the appearance of the coins.
     
  21. Vess1

    Vess1 CT SP VIP Supporter

    This forum seems to be obsessed with toning.
     
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