1943 steel cent composition

Spock just does the butcheringnot the eating :hail::kewl:
rzage:whistle::smile

 

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I'm not sure the zinc covers the edges.

 

I thought the answer to the op would be easy to find but boy was I wrong. Lots of info out there to read but little about the composition.
A wild guess is .015% zinc, based on copper plated zinc cents.
This link was good reading.
http://en.wikipedia.org/wiki/Lincoln_cent

 

This is from the Treasury's web site:

Production of the war-time cent was provided for in an Act of Congress approved on December 18, 1942, which also set as the expiration date of the authority December 31, 1946. Low-grade carbon steel formed the base of these coins, to which a zinc coating .005 inch thick was deposited on each side electrolytically as a rust preventative. The same size was maintained, but the weight was reduced from the standard 48 grains to 42 grains, due to the use of a lighter alloy. Production commenced on February 27, 1943, and by December 31, 1943, the three Mint facilities had produced 1,093,838,670 of the one-cent coins. The copper released for the war effort was enough to meet the combined needs of 2 cruisers, 2 destroyers, 1,243 flying fortresses, 120 field guns and 120 howitzers, or enough for 1.25 million shells for our big field guns.

The daimeter of a penny is .75 in. The total surface area (two sides) is ~.88 in^2. A coating .005 in thick is equivalent to .0044 in^3. Zinc weighs 117 grams/cu in, therefore, the zinc coating on the penny weighs .51+ grams. The total weight of the steel penny is 2.7 grams so the there is .51 grams zinc and 2.91 grams iron with a miniscule amount of carbon and other misc impurities.

Interesting factoid: the 1943 cents are the only US coins ever minted for circulation that contain no copper.

 

Since the strip was plated before blanking we can treat the zinc as two layers of metal 2 ten thousandths of an inch thick and 19mm in diameter if you work the math you get .000446 cubic centimeters of zinc. Zinc weighs about 7.5 grams per cc (working from memory on the density of the zinc.) so the weight of the zinc on the coin would be .0033 grams (This seems reasonable since previous calculations I have made on the weight of the copper plating of current cents has been in the .005 gram range.) So that would give a percentage of the zinc at .1% 99.9 % steel.

It isn't on the edges Look at the edges of an AU or Unc steel cent and you can clearly see the different metal layers.

 

I wonder if the 43 cent would have held up better if they had coated the blanks. I'm guessing that would have taken too much time.

 

Condor, please recheck your math; I have corrected mine (the Treasury web site gave the incorrect thickness of the zinc coating).

The diameter of the cent (www.usmint.gov) is .75 inches (slightly under 19mm), radius=.375 inches
The area of each face is (pi x R x R) 3.14 x .375 x .375 or .4418 square inches.
The total surface area is twice that, or .8836 square inches.
The thickness of the zinc coating (Public Law 77-815) is "no more than" .001 inches.
The weight of zinc (www.allmeasures.com) is 117 grams per cubic inch.
The volume of zinc is the area times the thickness, or .8836 x .001, or .000836 cubic inches.
Therefore, the total weight of zinc is volume times density, .000836 x 117 or .103 grams
The weight of a steel cent is 41.5 grams, therefore it is 41.4 grams steel and .1 gram zinc or 99.76% steel and .24% zinc (you were a lot closer than I was, but still over 50% off)

 

I'll double check my math when I also have a chance to double check a couple of the other constants. (I was having to try and remember the density pf zinc from memory and I'm sure it was off some.)

There is still something wrong with yours though. A 41.5 GRAM steel cent? I think that should be 41.5 grains. The steel cent had two different weights, 2.5 and 2.7 grams. I don't know which was first and which was later. For that reason I used a weight of 2.6 grams to do the weight percentage.

 

O well, with all that said I got two more MS 66's tonight on the HA auction block. One P and a D. I already had the MS67's S's (two of em shown posted earlier). They should be delivered within the week.

 

Diameter 19.05mm or 1.905 cm

radius .9525 cm

area ((.9525)^2)*3.14 = 2.849 cm2

Thickness of the plating This is the real question, The spec say no more than .001 inch but it could be less. I used the same thickness as that of the copper on our copper plated cents .0002 inch or .0005 cm

So volume of the zinc is 2 * 2.849 cm2 * .0005 cm = .00285 cm3

density of zinc is 7.133 gram/cm3(so my original figure was too high)

So mass of zinc in the plating is 7.133 gm/cm3 * .00285 cm3 = .02 grams

As I said earlier I used a weigh of 2.6 grams for the weight of the cent, it turns out that is too low. The two versions of the steel cent were slightly heavier than I thought and 2.7 is a better figure, so the zinc is (.02/2.7)*100 = .74% of the total weight

So 99.26% steel and .74% zinc.

If the plating was the maximum thickness of .001 inches (five times as thick) the final figures would be
96.3% steel 3.7% zinc

Now this is a HUGE variation. The problem is we really have no good figures on what the actual thickness of the plating was, just a maximum figure. I would guess the best estimate would be an average figure of 97.78% steel and 2.22% zinc.

 

This is an old thread... but I was browsing this thread while trying to figure this out, too. The exact steel composition was never mentioned, as far as I can tell. The only measurements that are given is the weight of the penny, that it's zinc-coated steel, and that the zinc coating is 0.0005" thick (from 1944's "Annual Report of the Director of the Mint").

However, I was able to find the composition of the 1943 steel cent (in bold below) indirectly. As you may already know, the US Mint also produced coins for other countries during WWII. One such country is Belgium, which the US Mint produced zinc-plated steel 2 Franc coins for.



According to Colnect.com, that particular Belgium 2 Franc coin has an exact composition of 93.8% iron, 1.2% carbon, and a 5.0% zinc layer. It also has the exact same composition as the 1943 US steel penny, according to Wikipedia:

"...the production of 25 million Belgian two franc pieces by the Philadelphia mint after that country's liberation from the Nazis. These coins were of the same composition and the same planchets as the 1943 cents, but they differed slightly in weight."​

https://en.wikipedia.org/wiki/1943_steel_cent

1.2% carbon makes a very high carbon steel... and there are many online references stating that the 1943 steel cent is composed of a low carbon steel (Would a low carbon steel coin be sufficiently hard for circulating coin purposes? If no, then higher carbon content would make more sense. I'm not sure about either yes or no answers on this). However, adding more carbon creates a harder coin (to an extent this is practical until it becomes too brittle), which makes sense for circulating coins, otherwise they may be too soft. And, the zinc coating's purpose was to help prevent rusting, so the steel core would likely have been optimized for its hardness-toughness, and not for its innate rust resistance property, which was inevitable for an un-coated steel coin with any amount of carbon balance. Unless Colnect.com's composition is incorrect, the exact composition seems to be consistent with the 1943 steel penny's function - high enough hardness and toughness to survive circulation, while having a thick enough zinc layer to prevent the steel core from rusting.

 

Wexler and Flynn's 'The Authoritative Reference on Lincoln cents ' does states that the composition was 95% low carbon steel and 5% zinc. Low carbon steel is usually less than 0.25%.

 

Interesting. What is truth?

 

I thought I felt the earth shake until someone mentioned this was 8 years ago and we are still alive.

 

The composition info listed on Colnect.com for the 1944 Belgium 2 Franc coin, which was made at the Philadelphia Mint out of the same planchet and consequently has the same composition as the 1943 US steel penny, is very specific. I wonder if someone used a metal analyzer to get the composition. Unless it's a typo and it's supposed to be 94.8% iron and 0.2% carbon.

 

Breen also says low carbon steel, with a 0.0005" ( inch) thick plating of zinc. I have a problem with that being interpreted as 5% ( by weight I assume) zinc, but it is tool late to get the calculator and brain figuring the planchett size area x that thickness value. The specific gravity value isn't that much different.

 

Great research!

 

We do know for a fact that from the primary source, the US Mint, from their 1944 director's report (below), that the zinc coating's thickness on either side is 0.0005", while the weight is 42.5 grains = 2.753954 grams. We can also physically measure the coin's thickness at 1.52mm, and the coin's diameter at 19.05mm.

We can figure out the exact composition by a) math, b) documented evidence, or c) metal analyzer. I like (c) the best . Does anyone have a metal analyzer they can shoot a cull 1943 steel penny with (beneath the zinc coating)?

Also, if the US Mint did use low carbon steel, it's curious to know why the Mint would use a low carbon steel if it tends to rust more easily with its higher iron content.

It's also interesting to see that the US Mint reports a weight of 42.5 grains or 2.753954 grams, yet many other sources state that it's 2.70 grams. Maybe someone measured one example at 2.70 grams a long time ago and that number stuck. Or maybe the ".5" grains was left out and 42 grains was converted to 2.72 grams and rounded to the nearest tenth. The same sources also seem to get the thickness wrong (off by one digit or off by 10 times at 0.005" instead of 0.0005"). Whatever the case, there's a disconnect between what the US Mint says and what other sources are saying. My uncirculated '43 steel penny weighs 2.73 grams, so its weight is closer to what the US Mint states.