Restoring zinc coins

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This suggestion is ONLY applicable to zinc coins.

Have you ever encountered a basal zinc coin? Apparently so corroded that you cannot read the inscription? Before you throw it away, try soaking the zinc coin in vinegar for an hour and a half or two hours, before washing in cold water and rubbing gently with your fingers under the water flow and then rubbing briskly on a piece of cloth.

You may be surprised as the results!

I hope to produce a Numisdoc article on restoring coins in the future, first though I need to obtain some more badly corroded and/or dirty examples to work with!

Matt
Quote: Matt ProbertThis suggestion is ONLY applicable to zinc coins.

Have you ever encountered a basal zinc coin? Apparently so corroded that you cannot read the inscription? Before you throw it away, try soaking the zinc coin in vinegar for an hour and a half or two hours, before washing in cold water and rubbing gently with your fingers under the water flow and then rubbing briskly on a piece of cloth.

You may be surprised as the results!

I hope to produce a Numisdoc article on restoring coins in the future, first though I need to obtain some more badly corroded and/or dirty examples to work with!

Matt
Your timing is uncanny, I picked up about a dozen 1 & 10 Reichpfennigs from a rummage box for 20 cents each and more than half of them have deteriorated to the point where the mint mark can't be read. Strangely the main designs and fields are well preserved. As you probably know mintmarks are the key to 3rd Reich issues so being only able to see them under 100x magnification is somewhat unsatisfying.

I'll try one with some left over white vinegar and let you know how it works out.
Non illegitimis carborundum est.  Excellent advice for all coins.
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Hello,

this is quite an interesting topic. I have some 1947 Zinc Albanian Leke, which have accumulated some dirt and some white residues.

What kind of vinegar you advice to use? I mean white, red, which fruit from or artificial, not by brand. With which kind did you try and had good results?

Thanks and regards
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Quote: lidianbHello,

this is quite an interesting topic. I have some 1947 Zinc Albanian Leke, which have accumulated some dirt and some white residues.

What kind of vinegar you advice to use? I mean white, red, which fruit from or artificial, not by brand. With which kind did you try and had good results?

Thanks and regards

The white residues are zinc oxide. These form when zinc is exposed to mositure in the presence of heat (don't boil zinc coins!!!). Zinc oxide is dissolved by vinegar, among other acids.

White vinegar, Or dilute sulphuric acid, but that can be dangerous and is not advisable unless you know what you're doing!

You don't want to use exotic 'flavoured' vinegars, just plain white vinegar you can get cheaply from a supermarket .

Matt
Matt, really nice topic.

Do you have any advice for Tin coins? I have a few WWII sen from Japan and I'd like to make them look nice.
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Quote: SmartOneKgMatt, really nice topic.

Do you have any advice for Tin coins? I have a few WWII sen from Japan and I'd like to make them look nice.
If you have tin coins which are in so bad a condition that you can not read the insription (and are therefore completely worthless and basal) then you have nothing to lose by experimenting. I have no experience with tin, but should I ever encouter any I'll let you know how I get on.

In the meantime, it is worth remembering that household oil, the stuff used for oiling hinges, dissolves iron oxide (rust). However, when iron oxidises it really does oxidise, and the rust often is the coin. removing it can remove the very fabric of the coin.

Matt
Is verdigris, that ugly green curse of copper and bronze coins, similar enough to rust to respond to light oil?
Non illegitimis carborundum est.  Excellent advice for all coins.
Make Numismatics Great Again!  
Quote: pnightingaleIs verdigris, that ugly green curse of copper and bronze coins
Yes it is. It forms on the surface of copper and brass when they are exposed to damp in contact with acid.

Matt
"In the meantime, it is worth remembering that household oil, the stuff used for oiling hinges, dissolves iron oxide (rust). However, when iron oxidises it really does oxidise, and the rust often is the coin. removing it can remove the very fabric of the coin."
  
  I just read this, but a while back I posted a question about a Indian head penny I had found, it has rust corroded to it but I wanted to keep the green, although what you mention here seems best, what do you think?
Taking a break from swapping for a while, but still interested in pre 1799 Spanish coins, I will make time for that!

Looking for pre 1783 coins
heres something i tried on a few zinc coins that were junk and it restored them well light a candle and dip your finger on the liquid wax then lightly rub it over them it creates a coding amazing how it works but  i wouldnt do it to any that were worth anything but its just a cool experiment i did on a few cheapos i got in large lot bags that werent in to good of condition becouse i noticed that same problem with the white oxidation corroding the coins and the wax restored them well enough to make them average again they never oxidizated after that it even kind of brought out the detail really nicely but i wouldnt recommend it on any but worthless ones
maybe not such a good idea but heres before and after my experiment
before

after
works better with darker wax
what it really does is stops it from oxidizing anymore then they already have
maybe i will try soakin one in vininger then rubbing down with wax maybe coin will last for ever i guess if i put a zinc coin in a cup of melted wax let it harden then bury it someone will find it in far future and be amazed how well it was preserved what a great archealogical find for them
Taken from:

http://metaldetectingworld.com/cleaning_coin_p19_zinc_tin.shtml

NOTE: All chemical cleaning methods are relatively safe. However, their use and application are entirely at the reader's risk. We assume no responsibility for damage to property or personal health.
 
CLEANING ZINC COINS

   Zinc was used for coinage only in emergencies and only for coins destined to have a short period of circulation.

   For example, zinc money occurs principally in many emergency coinages of German cities after the First World War and also in the small change of the Third Reich from 1940.

   It must be assumed that the raw material available was not always satisfactory. Zinc contains traces of lead, bismuth and iron. These impurities cause zinc coins to vary in behavior with chemicals. That is why removal of the unsightly zinc oxides by various chemical methods can cause unexpected discoloration on coins. This discoloration often occurs in different forms, even with coins of the same type.
 
The following methods can be used for cleaning zinc coins:
 
1) Mechanical cleaning of dirt from zinc coins can be done more vigorously than for silver. A hard brush is best, but a glass brush and an ink eraser can be used advantageously too.
 
2) Wet cleaning: dirt on zinc coins is most easily removed by softening in warm soapy water. This is done for as long as necessary. The coins then can be brushed with a stiff brush or a glass brush. It is also possible to rub the coins with the common salt, sprinkled on from a salt shaker, with the fingers or a cloth.
 
3) Immersion into a Hydrogen Peroxide bath, described on page 11, is applied briefly to remove the dirt.
 
4) Chemical cleaning: zinc coins can be cleaned very simply by rubbing them with a moist cloth that has been passed over Vitrolin Copper Soap. If the coating is heavy, the zinc coins can be steeped in Copper Soap Paste for five to ten minutes. Thorough soaking for a quarter to half an hour must follow.
 
5) Sulfuric Acid (H2SO4) Method: the best and at the same time the simplest method of removing grayish-white zinc oxidation is placing the coins in approximately 5% Sulfuric acid (diluted 1:20) and leaving them there for 10 to 20 minutes.
 
CAUTION: DILUTION OF SULFURIC ACID MUST ALWAYS BE DONE BY POURING ACID INTO WATER IN A FINE STREAM, NEVER by pouring water into concentrated sulfuric acid!
 
The coins are turned over several times with two wooden sticks. Neutralization is accomplished by immersion in 5% Sodium Hydroxide (caution: caustic soda) and rinsed thoroughly. They are then brushed.
 
Boiling in 5% Sulfuric acid or brief immersion of heated coins in concentrated sulfuric acid is not recommended as the coins at the conclusion appear far more spotted.
 
Zinc coins must be protected unconditionally from the effect of the atmosphere and its constituents, or they will darken again in a short time (a few weeks). This is best done by lacquering with Japanese lacquer. An oil film can be provided by kerosene or Ballistol.
Does it work with zinc plated coins as well, or do you run the risk of removing the plating?
Quote: Matt ProbertThis suggestion is ONLY applicable to zinc coins.

Have you ever encountered a basal zinc coin? Apparently so corroded that you cannot read the inscription? Before you throw it away, try soaking the zinc coin in vinegar for an hour and a half or two hours, before washing in cold water and rubbing gently with your fingers under the water flow and then rubbing briskly on a piece of cloth.

You may be surprised as the results!

I hope to produce a Numisdoc article on restoring coins in the future, first though I need to obtain some more badly corroded and/or dirty examples to work with!

Matt

Great information
Love zincs! Happy to leave them just the way they are and preserve them, of course, from further deterioration.
Quote: SmartOneKgMatt, really nice topic.

Do you have any advice for Tin coins? I have a few WWII sen from Japan and I'd like to make them look nice.
My only advice for tin/aluminum is not to use hydrogen peroxide. I've never had any success cleaning these coins, but peroxide destroys them.
This chemistry, so I was thinking there should be a common formula for this. After googling it, I found there is.

Basically, metal oxides are alkaline, so:
Oxide + acid --> salt + water

So dissolving oxide from zinc, tin, copper or iron, should work with any acid, be it vinegar (which contains acetic acid), sulphuric acid, or coca cola (which contains among other things phosphoric acid). Stronger acid = stronger reaction naturally.

Coca Cola Classic: pH 2.5
Vinegar: pH 2.4 - 3.5 depending on the concentration of acid
Sulphuric acid, around 10% concentration: pH 1 - 2

Oil is slightly acid, it's called "Fatty acids" right, I don't know if this explains why also oil works since oil is insoluble in water. Poor oils are more acid than better quality oils. Stearin, which candles these days normally are made of, is a kind of fatty acid.
I never have cleaned a zinc coin but the people at my coin club swear by (at leat for zinc pennies) oven cleaner spray.
Give me a dozen men who are not afraid to die, and I'll accomplish what all the Generals & Admirals with all their Armies & Battleships cannot. -Otto Skorzeny the best special forces commander ever.
I tried olive oil and table vinegar on my 1943 10 Dinara. Oil did nothing. Vinegar managed to lighten the coin from 60% Gray to 30% Gray. But because my coin is in the UNC condition I really want to return it to the Mint condition, means shiny, and to keep it this way.
Now what should I do? I haven't started to rub the coin with anything yet, before I will know exactly how it will affect the coin. Help please.
I bought this coin for couple of bucks and just received it. Coin looks very unusual, since mostly these types of coins are very dark grey, usually with white spots. But this one is very light, looks like aluminum. I know that while new these coins were like this, but since I bought it this cheaply I think that it was cleaned or dipped in some kind of material. What is your opinion ? With which material you could clean it to this degree ?

So I guess I will have to re-read all the posts and see if I missed something, I care less about "restoring" my zinc coins, and I did read many, many, many words concerning that aspect. I do though, very much want to "preserve" them. The only input on that I caught was from someone playing in wax... I mean, if it works, cool, but it seemed to be one persons experiment, which seemed to work, but.... Whats the best way to preserve zinc coins? Secondly, after someone suggests: taking them to the moon in a capsule is the best way.

What is the most economical way for an average collector to PRESERVE his zinc coins?

Thanks Much for all input :)
A wooden box would be perfect.
Quote: "michsignman"What is the most economical way for an average collector to PRESERVE his zinc coins?


​I soak my zinc coins in WD40 over night. Next day, use stiff, short (horse) hair brush to clean of anything that is loose. Then pat them dry with paper towel and put them in self sealing 2x2s, using and iron tow heat the edges to ensure the glue seals air tight. The WD40 stops any further corrosion ...
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Do not argue with ignorant people .. !! They will drag you down to their level, then pulverize you with experience ...
There ya go!!! thats my kinda answer... 500 yrs from now I'm less concerned... but between vinegar, mineral oil, vasoline, soy candle wax, and "WD-40" , I felt one of these should work. I was only concerned of a chemical reaction I hadn't heard of between zinc and ammonia ore something would either melt my coin into a slurp, or knock me out from the fumes... hehe... Thanks
I know from experience oils near metals either lubricate or totally prevent most corrosion, oxidizing, rust without any deterioration I know of. I just never played with zinc as a kid I guess... heh
Hello,

Cheap zinc coins can be cleaned just leaving them all night long or some hours in vinegar depending on how dirty they are. Dry them and then with a piece of cotton fabric and enough baking soda rub them. If the coin is too dirty just repeat the process but using less time. Rinse them with water, dry them and protect them with museum wax. They will look pretty good and all inscriptions and images will be readable.

Yes, but is there a way to make them shiny? This is how they were when just minted.
Liar! Don't trust him! Vinegar doesn't dissolve moisture or zinc oxide! I found out the hard way. I found my first Reichspfennig yesterday. And you can guess what happened. The vinegar dissolves the zink. Small bubbles are coming off the coin. (Hydrogen) Idk what called in English (entzinken) means removing zink from something. If you put this for like 1-2h in vinegar, it will dissolve completely. Don't listen to this dumbass.
Quote: "Alexander Georg"​Liar! Don't trust him! Vinegar doesn't dissolve moisture or zinc oxide! I found out the hard way. I found my first Reichspfennig yesterday. And you can guess what happened. The vinegar dissolves the zink. Small bubbles are coming off the coin. (Hydrogen) Idk what called in English (entzinken) means removing zink from something. If you put this for like 1-2h in vinegar, it will dissolve completely. Don't listen to this dumbass.
​You use some big words, for someone who is here for the first day!
...you can run,  but you can't hide...
Quote: "yvon"​=1em​​You use some big words, for someone who is here for the first day!
​🤣
Quote: "Kwasura"​I tried olive oil and table vinegar on my 1943 10 Dinara. Oil did nothing. Vinegar managed to lighten the coin from 60% Gray to 30% Gray. But because my coin is in the UNC condition I really want to return it to the Mint condition, means shiny, and to keep it this way.
​Now what should I do? I haven't started to rub the coin with anything yet, before I will know exactly how it will affect the coin. Help please.
​UNC coins shouldn't be cleaned. Althought I wouldn't do it. After cleaning a coin, the original mint state and/or build up patination will be lost forever. An expert will always know when a coin has been cleaned.
Always ready to swap within the Netherlands!  
Hello fellow collectors. After many years of research and experiments I finally came to conclusion. And it is not as good as I thought it will be.

First I want to end a discussion about cleaning or not cleaning your coins. Of course it is up to you, but please, never say never. Professionals are cleaning the coins all the time. After all this is how you see them in the museums. It is called "conservation" or "restoration", and it is very important to remove something that can destroy metal and to prepare the coin for the many years to come. Also patina is not something that can be "lost forever". Patina is natural oxidation of the metal, formed over the years. Just clean your penny and put it back to your pocket, see what will happen in a few months time. I am not worry about it. Of course, if you have a perfect coin with perfect patina - keep it. But how many of us this lucky? I know, I am totally running out of luck when it comes to zinc coins.

So, this is my conclusion, after trying everything I could think of...

Long story short... if it is not perfect - don't bother.

You won't be able to fix anything. Zinc is a merciless metal. Nothing is worst than zinc. Say, you are about to buy a very good looking zinc coin in apparently UNC condition, and the only think that is on your way - is this little "spot" or "stain". But you are sure you can fix it - how difficult can it be? Well, the answer is - forget it! You won't be able to do anything. It is never "innocent little spot", in fact it nothing but corrosion. It can look like spot, stain, fingerprint, stripes or something else, but it here to stay forever. Corrosion means that some of the metal is destroyed, and you will have to remove even more metal to get rid of it. Corroded coins can not be fixed, and for sure can not be considered UNC. Doesn't matter how big is the damage, damage is done.

Shame really. Many of the zinc coins are highly collectable. I personally struggling to get 1920 Yugoslavia. Even tough I am trying to avoid zinc coins as much as I can, but we like what we like, and collect what we collect.

So, when it comes to zinc coins - BU is UNC and UNC is XF. And you should always physically see it. Most of the time picture will be deceiving. Which makes purchase online almost impossible. And in result will make any decent zinc coin very, very expensive.

Welcome to the world of zinc coins... Good luck, and happy collecting.
After many years of collecting 3rd Reich issues, many of which are zinc, I've arrived at the same conclusion. If you can't learn to live with zinc related problems - go find something else to collect! You simply can't fix it and the attempted cure is always worse than the original problem. Apart from taking every possible measure to stop corrosion from getting worse and keeping problem free coins problem free, there's not much you can usefully do.

I've developed a real appreciation for the value of a pristine zinc coin and have been actively seeking them out. Their rarity means it's all but impossible to build a complete set of every date / mint mark but who doesn't love a challenge?
Non illegitimis carborundum est.  Excellent advice for all coins.
Make Numismatics Great Again!  
Most of the problems of zinc coins are present from the moment the planks where made. Zinc with certain impurities corrodes from within a well as outside, you just have to find a fault free specimen and try to stop deterioration from outside or be complacent with the state it is when you get it.
Quote: "Idolenz"​Most of the problems of zinc coins are present from the moment the planks where made. Zinc with certain impurities corrodes from within a well as outside, you just have to find a fault free specimen and try to stop deterioration from outside or be complacent with the state it is when you get it.
​Yes sir, zinc is an awful choice for making coins. I have an almost complete 3rd Reich collection by year and mint and out of all those hundreds of coins I have only two or three zincs which I'm fully content with. They are dark, without wear and have a pleasant sheen to them. I reckon the only difference from the day they left the mint is the inevitable darkening of the surfaces. I'm very proud of them, far more so than any of the big flashy silver 5 Reichsmarks I own.

If anyone has such coins to trade I'll offer most advantageous terms for the right coin(s).
Non illegitimis carborundum est.  Excellent advice for all coins.
Make Numismatics Great Again!  
Quote: "Idolenz"​Most of the problems of zinc coins are present from the moment the planks where made. Zinc with certain impurities corrodes from within a well as outside, you just have to find a fault free specimen and try to stop deterioration from outside or be complacent with the state it is when you get it.
​zinc rot,:o the bane of die cast collectors the world over for decades
Jamais l'or n'a perdu la plus petite occasion de se montrer stupide. -Balzac
Would like to offer to your attention this article on Slovak web site. I found it quite interesting.

Slovenský štát – mince 1939-1945 (SLST)
Just out of curiosity. Early on in the thread it was mentioned not to boil zinc coins. Can you literally dissolve USA pennies and other zinc coins by boiling them?
I tried using vinigar to clean a cheap zinc coin I have (https://en.numista.com/catalogue/pieces21159.html). I let it soak in rice vinigar (it's what I had) for about an hour, then wiped it off with a paper towel and rinced it in water and dried again. Here are the results:

Before


After


Like someone else pointed out, the corosion isn't something on the coin, like dirt, the corosion is the coin. When you clean the corosion off, you remove part of the coin, as can clearly be seen from these pictures. I have 3 other zinc coins (2 other 10 aurar coins and one 25 aurar coin), and I don't think I'll be trying to clean them.
Quote: "blue-m"​Just out of curiosity. Early on in the thread it was mentioned not to boil zinc coins. Can you literally dissolve USA pennies and other zinc coins by boiling them?
​You will not dissolve them, but boiling will trigger the corrosion. I've tried to boil zinc coin in water with baking soda. At first I was happy, soda removed an oxidation, and heating accelerated this process. But after some time the coin got covered in white dust, making the legend and other details almost invisible. It has something to do with the heating. Apparently you should never hear zinc coins.
hi does anyone know if this will work on brass coins as well? I've got a couple of brass coins with green and white spots.
Hi. Brass coins are totally different subject. Please stick to the topic.

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