Quick Acetone question

[ageka]

Electrolysis is effective but takes some basic knowledge of the process to avoid damaging the coins.

 

 

Yes like the time my friend hooked up the coin to the wrong electrode and ended up with a lot of corrosion pitting on the coin

[bigd349]

ust make sure that you get 100% acetone. Alot of times they mix it with other chemicals. That's not what you want. So must make sure you get the purest that you can get. It might not be 100% but I believe it will be 90%. I think that is what we used to get at my job. That is just about the purest, then I think it drops down to 75% and down even further.

[28Plain]

Yes like the time my friend hooked up the coin to the wrong electrode and ended up with a lot of corrosion pitting on the coin 

Yep, and if you allow the coin to contact the stainless anode, the coin can be welded to it, or can sustain a melted spot from the contact. The closer the coin is to the anode, the more action you get in breaking loose adhesions. Whatever comes off of the cathode gets more or less plated to the anode, so reversing the connection will ruin whatever you're trying to strip pretty quickly.

 

Electrolysis will remove encrusted oxidation, but the corrosion under the encrustation isn't helped by the process. Corrosion is irreversible. Thought I'd throw that in there to keep everyone from getting their hopes up too high. ;-)

[Burks]

Electrolysis is effective but takes some basic knowledge of the process to avoid damaging the coins.

 

Yup. Earlier I was messing around and put a penny and quarter in there. The quarter now has nasty crud plus copper on it. Kind of neat actually.

[Trantor_3]

The jewlery cleaner mentioned vibrates to much, and the coin if set on the bottom of the metal tray will scratch the coin, I tried it at work one time, I guess you could place a plastic container in it though??

 

You have to avoid at all time that the coin touches the metal tray.

 

However, the plastic baskest that these things come with, absorb most of the ultrasonic energy, reducing the cleaning power.

 

A nice solution would be to hang the coin in the water in a small contraption that won't harm the coin.

 

Also, the water needs to be de-inonized or distilled, to make sure it's clean and can absorb the stuff that comes off the coin. Also, cleaning works better if it's pretty warm (80°C is a temperature that's often suggested)

 

Here's a long page with lots of detailed info on ultrasonic cleaning on the web site of one of my customers, who specializes in (industrial) ultrsonic cleaning.

 

These smaller ultrasonic tanks are quite popular among metal detector fanatics, as they are extremely well in getting dirt (like sand and other stuff) of off objects without using drushes, tooth picks etc.

[ageka]

Yep, and if you allow the coin to contact the stainless anode, the coin can be welded to it, or can sustain a melted spot from the contact.  The closer the coin is to the anode, the more action you get in breaking loose adhesions.    Whatever comes off of the cathode gets more or less plated to the anode, so reversing the connection will ruin whatever you're trying to strip pretty quickly.

 

  Electrolysis will remove encrusted oxidation, but the corrosion under the encrustation isn't helped by the process.  Corrosion is irreversible.  Thought I'd throw that in there to keep everyone from getting their hopes up too high.  ;-)

 

 

I would like to make a small nuance

Corrosion can be reversed by a redox reaction but since the newly de oxydised metal will be new it will not have the same look as a stamped coin surface

In fact it may just fall of as metal dust

[28Plain]

You have to avoid at all time that the coin touches the metal tray.

 

However, the plastic baskest that these things come with, absorb most of the ultrasonic energy, reducing the cleaning power.

 

A nice solution would be to hang the coin in the water in a small contraption that won't harm the coin.

OK, here's my favorite method of suspending a coin in the ultrasound tank. Nylon cable ties come in many sizes and can be used to encircle the coin at 90 degrees to the faces. Just tighten the cable tie around the coin, make a small hanging hole in the tail end of the tie with a red hot paper clip and use the paper clip as a hanging hook to suspend the coin in the center of the tank. The only thing contacting the coin is the nylon tie and that only touches the rims at two spots.

 

The best method is to hang the coin from something other than a rack that spans the open top of the tank. The vibration from the transducers will be transmitted to the spots on the rims where the tie touches the coin if the coin is suspended from a ring rack such as the open top machines have for cleaning rings.

 

Hanging the coin from a freestanding frame of wire is best. It's easy to rig something up from stiff wire. I reveal coin cleaning secrets with trepidation here, knowing that I may become a pariah for contributing to the knowledge of coin doctoring. ;-)

[28Plain]

I would like to make a small nuance

Corrosion can be reversed by a redox reaction but since the newly de oxydised metal will be new it will not have the same look as a stamped coin surface

In fact it may just fall of as metal dust 

 

I didn't know that. Does it work on precious metals? It would seem that, even if the metal could be restored, any detail lost to corrosion would still be lost, making the repair ineffective for numismatic purposes.

[ageka]

I didn't know that. Does it work on precious metals?  It would seem that, even if the metal could be restored, any detail lost to corrosion would still be lost, making the repair ineffective for numismatic purposes.

 

Gold cannot oxidize in other words there is no molecule or formula with oxygen and gold in it

So it is either the copper or the silver in it that is oxidised or made into a salt like a sulfide or chloride or whatever

 

This copper or silver oxidation can be reversed with a redox reaction

 

When you use a dip it is normally an acid bath or a base bath and you strip away the corrosion and your coin will be a few micrograms lighter because you lost that metal in the salt by stripping away the salt

 

If you redox the coin you will not loose weight and the salt will reconvert to metal

but that metal will be reconstituted metal having no memory of its original state as minted metal

 

The redox can be done electrochemically ( beneath is a passive method without putting 12 volt on the coin )

 

http://scifun.chem.wisc.edu/HomeExpts/TARNISH.html

 

or by pure chemical reaction from a reducing agent eg for silver

 

http://www.chemicalland21.com/arokorhi/ind...THIOSULFATE.htm

 

I think if a salt is eating your coin allive and you have to try and stop it both methods would work if they do not work to your satisfaction you can still buy the silver dip or copper dip and go the full treatment

[28Plain]

Yes, of course, the base metal in the alloy is what corrodes. I was picturing the pitting on a silver/copper alloy coin being reversed by magic. Guess I was fantasizing. ;-)