One for the chemists here - is manganese especially reactive with air?

lsica

Looking to understand how the toning on War Nickels might differ from other copper/silver alloys because of the addition of manganese to the alloy...

Edit - corrected for spelling to help future search results

braddick

Manganese is relatively inert despite it being a little more electropositive than its neighbors in the periodic table. It is not particularly reactive to air. The surface of manganese lumps oxidize to a minor extent but when it is finely divided, it becomes pyrophoric and burns in air. It tends to form the oxide Mn3O4 and the nitride Mn3N2. Temperature for such reactions are reaches more than 500 °C.

3Mn(s)+2O2(g)−→ΔMn3O4(s)

3Mn(s)+N2(g)−→ΔMn3N2(s)

Manganese is also said to not react with water under normal conditions although some sources say it reacts with water to liberate hydrogen gas.

For your thermite reaction with war nickels, I haven't found any Mn−CuO reaction but I did find Al−Mn2+− thermite reaction.

CaptHenway

FWIW, back in the 70's when I was working at Coin World in the Collectors Clearinghouse Dept., I wrote to the head of the Mint Lab to ask him why so many of the wartime nickels came heavily laminated. Whoever it was (the name escapes me at the moment) had been working at the Philadelphia Mint during WW2, and he said that because of the huge demand for coins they were storing ingots of non-precious metals in an open courtyard where they were exposed to rain and snow.

The manganese ingots in particular became heavily oxidized, and he said that they should have scaled them (scoured them with a wire brush) before throwing them in a melting furnace, but they did not bother to do so because they were so busy. He said that the manganese oxide cause the laminations. I would assume that it affected the toning as well.

TD

Mr_Spud

Study on the microstructure, mechanical properties, tarnish and corrosion resistance of sterling silver alloyed with manganese
https://d1wqtxts1xzle7.cloudfront.net/72132938/j.msea.2006.09.10620211010-2452-1q5qmlp-libre.pdf?1633929191=&response-content-disposition=inline;+filename=Study_on_the_microstructure_mechanical_p.pdf&Expires=1731780610&Signature=PGjS6qplq-IAwdtZ-QxbnMtTqg7l2zvsYrmcw56cKv9EZJcOIYcO0BBKnzpMdSu0iMJ7M-ZJ~r9tUHt5kk6dqcnPTXomqbGx0scBSonBHNHqd0QXCXljSP5bJFMIocdDwM69Xk5r4vgkFQVP9lwnhlRd01lYn4bbcDNHDBiRchM5n5XLwcVL1U7cHA3q~8jMBXmDxm7KA6bAkxoTUwIRiQ2ZraZOeFr64rAAO~15rCOpgc~wwQdFTtO5V69joBoQS2S1tT314u89A-AlogS3CmYuy3QnVaFTAdsMQdU7wQaIA~6Tu2G04BA9S1DTUAxMRIg6vUYH-5TLLyxFo1uZqQ__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA

This has some info on manganese/silver alloys “Tarnish Resisting Silver Alloys”
https://nvlpubs.nist.gov/nistpubs/nbstechnologic/nbstechnologicpaperT348.pdf

jmlanzaf

You have to look at the alloy as a whole not the separate components

FlyingAl

@jmlanzaf said:
You have to look at the alloy as a whole not the separate components

I'd wager you'd also have to take a look at what colors the resultant possible reactions would produce. The composition of war nickels is drastically different than "normal" nickels.

lsica

@Mr_Spud said:
Study on the microstructure, mechanical properties, tarnish and corrosion resistance of sterling silver alloyed with manganese

And stuff like this is why this is still the best coin forum on the Internet

Mr_Spud

This patent discusses smaller amounts of manganese alloyed with silver “Sterling silver manganese alloy compositions”
https://patents.google.com/patent/US20050211342A1/en

Mr_Spud

While I was doing a literature search on manganese alloys, I stumbled on this cool looking book and just got the kindle edition off of Amazon, looks like a good read

Clackamas1

@CaptHenway said:
FWIW, back in the 70's when I was working at Coin World in the Collectors Clearinghouse Dept., I wrote to the head of the Mint Lab to ask him why so many of the wartime nickels came heavily laminated. Whoever it was (the name escapes me at the moment) had been working at the Philadelphia Mint during WW2, and he said that because of the huge demand for coins they were storing ingots of non-precious metals in an open courtyard where they were exposed to rain and snow.

The manganese ingots in particular became heavily oxidized, and he said that they should have scaled them (scoured them with a wire brush) before throwing them in a melting furnace, but they did not bother to do so because they were so busy. He said that the manganese oxide cause the laminations. I would assume that it affected the toning as well.

TD

That is some great history. Thank you for sharing. I always wondered myself.

Married2Coins

@CaptHenway said:
FWIW, back in the 70's when I was working at Coin World in the Collectors Clearinghouse Dept., I wrote to the head of the Mint Lab to ask him why so many of the wartime nickels came heavily laminated. Whoever it was (the name escapes me at the moment) had been working at the Philadelphia Mint during WW2, and he said that because of the huge demand for coins they were storing ingots of non-precious metals in an open courtyard where they were exposed to rain and snow.

The manganese ingots in particular became heavily oxidized, and he said that they should have scaled them (scoured them with a wire brush) before throwing them in a melting furnace, but they did not bother to do so because they were so busy. He said that the manganese oxide cause the laminations. I would assume that it affected the toning as well.

TD

I was not there but he was; however, this struck me about his answer: The dirty, corroded, ingots were melted. The only thing I can think of is all those impurities got rolled out inside the planchets. Would any oxidized Mn not blend back to it's unoxidized form? Or. did it become like the dual mix we see in "Woodies" that often laminates. It is a shame more people did not pump the brains of the old Mint employees like TD did. Thanks!