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How do I stop copper oxidation?

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Q. I'm refinishing a 60's hanging lamp with many copper shade parts like fins. The pieces were/are painted white on the inside and the outside is normal orange copper color. They were encrusted with a million years of nicotine and had a thick coating of some sort of finish on them. I brush cleaned some, dipped some in paint remover, polished some, and lacquered some. No matter what I do they are oxidizing into black patchy things! How can I keep them 'orange'? I thought the professional cleaning and lacquering would stop this but it hasn't.

Thanks....

tom melville
- pittsfield Massachusetts


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A. Hi Tom.

There may be something wrong with your cleaning and lacquering process. I don't know what exactly, but if the parts are cleaned so that they are 'orange', and there are no residual contaminants on the surface, and then they are properly lacquered, I think they should stay 'orange'. You might talk to the site's supporting advertiser, G.J. Nikolas, specialists in this field, who offer lacquers customized to the particular need. Good luck.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


April 23, 2010

A. I haven't tried it yet, so I don't actually know how good it works, but Permalac.... do a search on that, and that is supposed to be good for all metals, outside, including sea spray and UV for 10 years (personally I'm looking for something to cover the copper I will be using in an "L" shaped bartop (8' x 4') that will also have an Environmental Tech EnviroTex Lite [linked by editor to product info at MisterArt] coating over it, I just don't want the copper to start to green up a few years down the road when the only fix will be to redo the bartop itself... I believe I will be ordering this...)

Erik Levasseur
- East Coast



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Q. Several members of my jewelry class and I are interested in anything besides jeweler's lacquer that one can use to prevent copper from darkening. In addition, is there anything that can preserve a deliberately colored piece of copper without changing the colors? By this I mean, I have deliberately fire scored copper to get an amazing range of colors, but the minute you put jeweler's lacquer on the piece, the color changes. If anybody has any suggestions, I would appreciate hearing them

Carla V. Echandi
- Omaha, Nebraska


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Q. I am currently building a copper sculpture out of half inch copper pipe. I am nearing the end and would like to know if anyone has any information regarding how to properly clean copper for clearcoating. Also, is there a good product out there that works to clearcoat copper and keep the shine and pipe from oxidizing?

Mike Lawlor
product design - Poughkeepsie, New York


+++++++

A. Hi Carla and Mike. Benzotriazole [link is to product info on Amazon] is a good temporary tarnish preventer for copper, and applying it before the lacquer may help keep it bright. I think some lacquers have a small amount of benzotriazole or similar preservatives in their formulation.


Carla, unfortunately there is probably a second problem for you. Yes, all lacquers greatly detract from the pretty colors of heat oxidized copper. I am not a hobbyist in that field, but the reason is that, while some of the colors may be actual pigments, many of the colors are diffraction colorations are caused by very thin (partial wavelength) refractive films of transparent oxides or oils (like the rainbow sheen of a drop of oil in a water puddle). When this this transparent film is coated with another transparent film, the combined thickness is not partial wavelength anymore and they naturally lose their refractive capability. I think you will find letter 2662, "Preserving heat coloring of copper when clear coating" interesting. Good luck.

wikipedia
Iridescence


pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


October 2, 2008

A. I notice several questions about stopping the oxidation process of copper. I worked with copper exclusively as an artist for several years and found through trial and error that aerosol polyurethane works very well. Great care must be taken in applying it so that it does not spot or puddle, but I have an oxidized painting on sheet copper in my dinning room that is 8 years old and still lovely burnished copper. Chemically, it literally smothers the surface instantly denying oxygen. A clean surface is a must, as is a uniform and complete application. Missed spots, however small will eventually discolor. I hope this is helpful to some.

Christopher Rico
artist - Clinton, South Carolina


February 28, 2010

?? Chris, You suggested the Aerosol Polyurethene; can this be used on an outdoor application with the UV rays? Will it peel on gutters?
Regards

Frank Ball
- Millis, Massachusetts



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Q. My copper ring is turning my finger green/blue. I got married a week ago and instead of buying rings, we had them made out of copper wire we bought at a hardware store. They came out great but turns out that the ring seems to be oxidizing where it meets my finger and turning it green/blue. First, is this dangerous? Second, what can I do to stop this from happening? Thanks for your help. By the way, my girlfriend's finger has not been turned green/blue by her ring. It is also not as tight on her finger.

Richard Gil
student - Chicago, Illinois


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A. People wear (and swear by) copper bracelets, and a few even claim it wards off arthritis, so I'd say it's not dangerous, Richard.

But the rings should probably be periodically lacquered to keep them looking good and prevent the greening. If you don't have brass lacqueramazoninfo for the whole ring, you could try clear nail polish on the parts that touch skin perhaps.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


August 30, 2010appended

Q. I make chainmail jewelry and I want to find a way so that the bronze links on my pieces don't tarnish quickly. Any home concoctions or products that will prevent the aging of my rings?

Christopher Wright
Artist - Beach Park, Illinois


March 12, 2012appended

Q. I am new to the jewelry business. I am buying and selling jewelry wholesale and would like to know if there is a lacquer or coating I can apply to all finishes. If not, how can I tell what the underlying metal is to coat it appropriately? I have been using clear nail polish but I would like something more long term.

Kiah Saundrie
Wholesaler - Memphis, Tennessee, USA


March 24, 2012

A. Sodium silicate is a useful water soluble substance for creating a gas proof seal on most metals. It belongs to a family of chemical compounds known as water glasses =>

A common use for sodium silicate used to be for preserving eggs. It works by bonding to the calcium in the egg shell and forming a gas tight seal, which prevents oxygen from passing through the egg shell and allowing the egg to go rotten.

Sodium silicate readily bonds to most metals, BTW, how many of you know the element calcium in the egg shell is also a metal? Check out Sodium silicate on Wikipedia or Google.

I suggest that you protect your sodium silicate oxygen barrier with a tough and durable vanish, or lacquer.

I hope this helps someone.

Mark Lacey
Picture framer - Newton Abbot, Devon, England

Sodium Silicate



May 21, 2012appended

Q. I am an artist working in Hawaii where I am dealing with salty air and humid temps while working in copper. I noticed my copper has tiny spots on it which I try to "sand/buff" out and the copper gets very shiny. But, in a days time' the spots are back. Also, I am using a torch for coloring and putting in images with hand tools. Now I need a product that coats the copper, makes it glossy and stops the oxidation. Any ideas out there? Thanks!

Jenny David
- Hilo, Hawaii, USA



April 12, 2013

Q. Is it possible for an aluminum part that has been plated with acid copper to oxidize after it has been coated with a clear spray lacquer? I'm referring to the plating and not the substrate.

Robert Curry
- Portland, Oregon, USA
  ^- Privately contact this inquirer -^


July 12, 2013

A. Robert,
Yes, very possible. Did you apply Zincate? It wasn't just Cu on clean aluminum was it? Assuming you used a great process with a nice undercoat and did all kinds of testing I would look at condition and rates. In other words, supposing the process was followed and it is a known good process, I would be sure that the parts were dried overnight and that the clear coat was applied on ambient temperature parts.

If the clear coat looks great and there is a problem underneath it then I would suspect the plating process was not correct and the problem could be anything like contaminated baths but often it is a lack of rinsing and drag-out. If a drop or two of the previous chemical is still on the part and not rinsed off, it will cause a small void and after plating imperfections may not be visible unless heavy testing is done including destructive testing. Good luck.

blake_kneedler Blake Kneedler
Santa Clara, California


Darkening of copper plated aluminum parts after clear powder coating

February 25, 2014

Q. I have a customer that want some aluminum parts copper plated and powder coating clear coat, so i tried the following

double zincate
copper plate alkaline
buff
thoroughly clean with solvent
dry with air as fast as possible in order to avoid lost of brightness
powder coat
bake

And I was worried about the cleaning, but the problem was that the first parts that I painted were darker than the last ones -- so the question is how do I avoid this darkening of the parts? I think they get dark due to the natural darkening of the copper due to exposure during the time we have to wait to complete the batch, before baking.

Daniel Hernandez
- Bucaramanga Santander Colombia
  ^- Privately contact this inquirer -^

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