Arresting corrosion on copper?

True, but the point I was making is the only thing you could get with your ingredients is some oxide of copper.

 

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With that in mind, it has been mentioned frequently that a freshly cleaned copper surface tends to be QUITE reactive. I think a thin copper oxide layer might passivate the surface towards further reaction if it can be made to happen slowly. Thoughts?

 

Copper, especially. There's a reason why it was/is used for roofing material; it's all but impermeable once the patina is formed and does not further deteriorate.

 

Granted, but I'm not talking about going as far as a patina, I would like to stop at the "passivated" stage.

 

I'd be inclined to think not; there always seems enough sulfur dioxide around to eventually turn it green. You'd have to arrest atmospheric exposure.

 

Once again, point well taken, but hopefully, passivated would include some modicum of protection against further reaction.

 

Maybe that does what everyone swears about Verdi-care.

 

Shellac.

 

A very tight fitting plastic holder... : - )

 

Either way, it's a pretty tight-fitting holder. One's just....a little tighter than the other.

 

I had some cents in those littleton green folders, supposedly archival quality. After a year I just checked on them and the green stuff developed in specks over many, sometimes growing into patches. I don't where I live and put my coins has never turned this residue up. So I'd like to add that traditional or old style pop in folders aren't such a great idea.

 

Hummm Doug, I thought you had VC figured out by now. This is incorrect.

VC contains corrosion inhibitors and verdigris neutralization reagents. As long as a treated coin is properly stored verdigris will NOT reform nor grow if it remains.

 

Generally true, but not completely. Verdigris in itself can provide feed materials. Think about it on a micro-scale, verdigris contains micro-components (i.e. acids, anions, etc.) that can contribute to a self-sustaining reaction. This is well known by ancient collectors with coins that have hydrochloric acid induced verdigris (i.e. the horrible, incorrect term called 'bronze disease'). In chemistry, reactions occur in equilibrium, meaning they are never totally to completion. There is always evidence of the starting materials remaining, they may be minuscule, but they are there at some level. As things shift around due to the equilibrium, you have activity.

Verdigris is quite complicated, while the formation forces at work, primarily on a macro-scale with air and water, you must also consider the dynamic electrochemistry involved. All metals exhibit micro-currents within them. Electrons are constantly flowing and the effect is exacerbated by temperature fluctuations. This drives electrochemical reactions on a micro-scale, which, given enough time, can eventually build verdigris to where you can see it if feed materials (old verdigris) are present.

 

"Bronze disease" is a term I cannot stand, diseases cannot infect metal. The correct description of "BD" is hydrochloric acid induced metallic corrosion. Most conservators use very strong bases to neutralize the acid, halt the reaction and displace the verdigris. Of course, for moderns, this is a HORRIBLE method since it will strip the surface....but ancient coins are a whole different ballgame in the conservation world.

Ancient coins are much more complicated when compared to fresh verdigris. Given the time scale, verdigris can actually become so advanced it mineralizes. When that happens, I no longer even call it verdigris, it is not, it is a mineral deposit and cannot be removed without mechanical means.

Personally, I've done minimal testing with VC on ancients because of the mineralization process. However, if it's still in the verdigris stage due to improper storage during modern times, VC can often address and neutralize it. It may not fully remove the verdigris but it will neutralize it. VC is only designed to address light to moderate-type verdigris.

 

But "BD" is easier to say than the alternative: HAIMC. I just call the stuff corrosion.

 

Anything EXCEPT a disease! Even "BC" (Bronze Corrosion) would be better than disease!!!

 

Thank you very much Bad Thad. sounds like the answer I was looking for. I,m going to order some. These coins meet all the criteria you mentioned. classic head cents. best regards

 

I personally think diesel fuel, would be the first stage to this one. I used to find old model t jacks in junkyards, like a concretion formation. I would soak in diesel for a year . it would dissolve and loosen the rust mineralization. then clean with soap and water.

 

I yield to someone who can pick the nit better than me.