1971 D Half dollar on struck on solid copper planchet 1 1

[Stephen J]

I found this today going through bank rolls, can you tell me what I have? 0% nickel clad is present. It weighs exactly 4.000oz. Obverse wear does not have the grean but same lettering and detail wear condition. Thanks

Edited January 31 by Stephen J

[J P M]

Welcome, the short answer would be. Your coin looks like it has been outside in the ground for a long time.

Edited January 31 by J P M

[Greenstang]

Just a regular 50 cent coin with environmental damage.  
Still worth 50 cents though.

[Mike Meenderink]

You have a severely corroded coin that has "lost" its clad layer due to the exchange of copper from this process. The clad layer is still there it's just covered in copper molecules now and starting to get green verdigris. The brown side is corroded as well but that side had more oxygen access, and the green verdigris turns brown black. Value 50c

[RWB]

On 1/31/2024 at 10:34 AM, Mike Meenderink said:

You have a severely corroded coin that has "lost" its clad layer due to the exchange of copper from this process. The clad layer is still there it's just covered in copper molecules now

Please explain the chemistry of how this happens. What happened to nickel?

[Stephen J]

On 1/31/2024 at 9:34 AM, Mike Meenderink said:

You have a severely corroded coin that has "lost" its clad layer due to the exchange of copper from this process. The clad layer is still there it's just covered in copper molecules now and starting to get green verdigris. The brown side is corroded as well but that side had more oxygen access, and the green verdigris turns brown black. Value 50c

That's a viable explanation, however my issue with it is the weight is exactly the same (not close, but spot on) with normal halves and all of the lines, including the D mint mark are all clear and sharp (under magnifying glass, picture doesnt do it justice). I dont think an "exchange of copper" process would still keep the lines as sharp as they appear while not changing the weight after loosing 8% of its material content. I thought through what you've said before I posted but it doesn't pass to me as a severely weathered coin. 

Edited January 31 by Stephen J

[Sandon]

    Welcome to the NGC chat board.

    As others have stated, your 1971-D half dollar was very likely struck on a normal planchet, but its surfaces have corroded, probably from being buried in the ground. The outer layers of a clad coin are composed of a 75% copper, 25% nickel alloy. This alloy interacts with chemicals in the ground and other environments and forms chemical compounds on the surface, darkening and/or developing bluish green corrosion in this way. I have observed this on both clad coins like this and on nickels, which are composed of the same copper nickel alloy in their entirety, that have been dug from the ground.

   I don't think that @Mike Meenderink 's explanation is accurate and request that he refer us to a reliable source for this explanation.

[Greenstang]

The average weight of a clad 50 cent is 11.34g. Don't know where you got the weight of 4.000 oz. from, no coin weighs that much. When weighing coins always in grams to at least two decimal points.   Environmental toning usually doesn't change the weight too much unless it is corroded. 

Edited January 31 by Greenstang

[Stephen J]

On 1/31/2024 at 10:31 AM, Greenstang said:

The average weight of a clad 50 cent is 5.67g. Don't know where you got the weight of 4.000 oz. from, no coin weighs that much. When weighing coins always in grams to at least two decimal points.   Environmental toning usually doesn't change the weight too much unless it is corroded. 

The scale I have is accurate to .1g and .005oz.  I just changed the units. For reference, normal halves weigh in 3.990-4.000 from the few I compared it to. It was a short term buy, I know I need a gram scale, had one before a long time ago. I need another one.

[Mike Meenderink]

On 1/31/2024 at 8:11 AM, RWB said:

Please explain the chemistry of how this happens. What happened to nickel?

1. Galvanic Corrosion: While cupronickel doesn’t rust like iron or steel, it can still corrode over time under specific conditions, especially when exposed to certain soils or saltwater. This type of corrosion is known as galvanic corrosion. It occurs when two different metals come into contact with each other in the presence of an electrolyte (such as seawater). The more noble metal (in this case, nickel) protects the less noble metal (copper) by sacrificing itself. In cupronickel, the nickel acts as the protective layer, preventing significant corrosion²³.

Edited January 31 by Mike Meenderink

[Mike Meenderink]

In other words, the CuNi clad layers had most of its nickel content "dissolved" out. The clad layer is still there but it has lost all or most of its nickel content.

Edited January 31 by Mike Meenderink

[Mike Meenderink]

On 1/31/2024 at 8:29 AM, Sandon said:

 I don't think that @Mike Meenderink 's explanation is accurate and request that he refer us to a reliable source for this explanation.

 

On 1/31/2024 at 10:43 AM, Mike Meenderink said:

1. Galvanic Corrosion: While cupronickel doesn’t rust like iron or steel, it can still corrode over time under specific conditions, especially when exposed to certain soils or saltwater. This type of corrosion is known as galvanic corrosion. It occurs when two different metals come into contact with each other in the presence of an electrolyte (such as seawater). The more noble metal (in this case, nickel) protects the less noble metal (copper) by sacrificing itself. In cupronickel, the nickel acts as the protective layer, preventing significant corrosion²³.

Edited 3 minutes ago by Mike Meenderink

 

[Stephen J]

On 1/31/2024 at 1:05 PM, Mike Meenderink said:

 

 

Good explanation, so it really just means that it's an old beat up coin and not a mint error. Dang. Thanks for the info though I have learned something new today. 

Edited January 31 by Stephen J

[Mike Meenderink]

yUp

[EagleRJO]

On 1/31/2024 at 6:53 AM, Stephen J said:

It weighs exactly 4.000oz. 

That weight doesn't make sense.  Can you post a weight with at least a 0.01g accuracy?  The mint spec for this 1971-D 50C with a 75% Cu & 25% Ni cladding over a solid copper core is 11.340g.  I suspect with the minor corrosion shown that it has lost a little weight, but it may not be significant enough to be outside the weight tolerance of 0.454g for that coin.

On 1/31/2024 at 10:34 AM, Mike Meenderink said:

You have a severely corroded coin that has "lost" its clad layer due to the exchange of copper from this process. The clad layer is still there it's just covered in copper molecules now and starting to get green verdigris.

On 1/31/2024 at 1:43 PM, Mike Meenderink said:

1. Galvanic Corrosion: While cupronickel doesn’t rust like iron or steel, it can still corrode over time under specific conditions, especially when exposed to certain soils or saltwater. This type of corrosion is known as galvanic corrosion. It occurs when two different metals come into contact with each other in the presence of an electrolyte (such as seawater). The more noble metal (in this case, nickel) protects the less noble metal (copper) by sacrificing itself. In cupronickel, the nickel acts as the protective layer, preventing significant corrosion²³.

Hmmm, is it that the coin "has 'lost' its clad layer" or is it that "the clad layer is still there"?  Looks to me like it was in the ground and simply has some surface corrosion, with a weight I am guessing will be just slightly less than the mint spec weight.

And you are just describing the method of corrosion.  There is nothing there about any "exchange of copper" or being "covered in copper molecules" which sounds like your much vaulted "molecular copper effervescences" process you keep mistakenly referring to for any brown colored clad coin, without any valid source to explain your incorrect theory that the solid copper core migrates through the solid Cu-Ni cladding to the surface of the coin.

On 1/31/2024 at 2:11 PM, Stephen J said:

Good explanation

No it's not.

[Mike Meenderink]

You can either believe science or EagleRJO. Your choice

[EagleRJO]

On 1/31/2024 at 2:43 PM, Mike Meenderink said:

You can either believe science or EagleRJO. Your choice

If that is "science" where is the reputable source for reading about this molecular copper effervescence?

[Mike Meenderink]

On 1/31/2024 at 11:59 AM, EagleRJO said:

If that is "science" where is the reputable source for reading about this molecular copper effervescence?

That statement made by me was a descriptive term used to describe the reason behind the coloration of an improperly annealed (over heated) coin in a completely different thread. Read about what happens to an over heated planchet when it is sent into the wild. Get back to me. 

[EagleRJO]

On 1/31/2024 at 3:31 PM, Mike Meenderink said:

That statement made by me was a descriptive term used to describe the reason behind the coloration of an improperly annealed (over heated) coin in a completely different thread. Read about what happens to an over heated planchet when it is sent into the wild. Get back to me. 

I was referring to your claims in this topic about there being an "exchange of copper" such that the coin was "covered in copper molecules", regardless of what you want to call it.  At what reputable source can I read about this "science" you are claiming is the case here.

[powermad5000]

On 1/31/2024 at 5:53 AM, Stephen J said:

It weighs exactly 4.000oz

Hello!

I simply cannot accept any of the weights given in this thread. I think you need a new scale.

Converting 4.000oz to grams is the equivalent of 113.3980925 grams. A Morgan dollar is supposed to weigh 26.73 grams. Your given weight then is over the weight of 4 Morgan dollars and the subject is only one Kennedy Half.

Outside of the discussion taking place here, I see a Kennedy Half dollar with environmental damage. Whether it was buried in the ground or sitting in a curb for a long time I don't think is utterly relevant as it is simply a damaged coin at this point.

[RWB]

On 1/31/2024 at 1:43 PM, Mike Meenderink said:

1. Galvanic Corrosion: While cupronickel doesn’t rust like iron or steel, it can still corrode over time under specific conditions, especially when exposed to certain soils or saltwater. This type of corrosion is known as galvanic corrosion. It occurs when two different metals come into contact with each other in the presence of an electrolyte (such as seawater). The more noble metal (in this case, nickel) protects the less noble metal (copper) by sacrificing itself. In cupronickel, the nickel acts as the protective layer, preventing significant corrosion²³.

So, should all clad coins be precoated with ferrous sulfate?

MM's explanation is satisfactory for the Kennedy half. We can speculate that if it were dug from common acidic soil, an initial corrosion rate of 0.005mm for the first year or two is reasonable, and approximately 0.002mm per year thereafter for 75-25 copper nickel clad alloy. Apply these rates to the thickness of half dollar cladding to get the number of years of burial necessary to sacrifice almost all the nickel. [See. "Copper Alloys in Seawater: Avoidance of Corrosion," R. Francis, CDA-Publication 225 - February 2016.]

MM just does not have the chemical background to accurately explain his "... 'exchange of copper' or being 'covered in copper molecules' which sounds like a much vaulted 'molecular copper effervescences' process" he keeps mistakenly referring to.

[VKurtB]

On 2/1/2024 at 2:10 AM, RWB said:

So, should all clad coins be precoated with ferrous sulfate?

MM's explanation is satisfactory for the Kennedy half. We can speculate that if it were dug from common acidic soil, an initial corrosion rate of 0.005mm for the first year or two is reasonable, and approximately 0.002mm per year thereafter for 75-25 copper nickel clad alloy. Apply these rates to the thickness of half dollar cladding to get the number of years of burial necessary to sacrifice almost all the nickel. [See. "Copper Alloys in Seawater: Avoidance of Corrosion," R. Francis, CDA-Publication 225 - February 2016.]

MM just does not have the chemical background to accurately explain his "... 'exchange of copper' or being 'covered in copper molecules' which sounds like a much vaulted 'molecular copper effervescences' process" he keeps mistakenly referring to.

Sounds like it needs an Alka-Seltzer tab. Plop, plop, fizz, fizz.