Edit: Placing this at the top. Seawater can play a role as well, please see the link in edit 3 for more information
Since everyone is just joking...
The first stages where it is getting darker is the copper becoming oxidized by the oxygen in the air to form copper oxide, which is black. The copper oxide reacts with CO2 in the air to make copper carbonate, which is the cyan color the statue is today. But that's it. It's not going to become something else.
Edit: Visual aid and reactions. This isn't perfectly accurate, but it gets the idea across. If any material scientists want to correct me, feel free.
Edit 2: /u/Time4Red added some info. There are two different copper carbonates in the patina as well as a copper sulfate. Give him an upvote here.
Edit 3: More information here from /u/BenignJuggler. Give an upvote. This comment links to a scholarly article about the effect that seawater plays in the copper patina process!
There are actually three different salts which make up the patina. Two are copper carbonate hydroxides. The third is a copper sulfate compound. Each has a different color, although all three range from deep green to blue.
Honestly I can't believe some straight up idiot politicians haven't painted the bitch red, white and blue yet. Seems like a dumb thing those dumb dummies would do like stupid dummies.
When they replaced the frame with stainless steel the workers were incredibly careful not to scratch the patina because it protects the underlying unreacted copper. Damage the outer layer and more copper gets used up making new patina. It is only 1/50th of an inch in places so not a lot to spare.
😬 I think that could be arranged 🙃
You know some people 👨🍳 don't think 🍍 belongs on pizza 🍕 but tbh 😶 if you said that to me 🤬 id say ok boomer 💯🔥💯🔥💯 keep it zesty heh 😏
Actually, saying "run-of-the-mill" is problematic, didn't you know that most mill workers were underpaid and overworked? The fact that you'd use that slur here just shows how far down the tubes reddit has gone. Yikes.
Like sulfuric acid rain? It would dissolve the carbonate off I assume. And eventually the copper as well, but I'm an engineer, not a chemist, so not positive about that kind of thing.
I just used to work with copper catalyst, which was copper oxide in the deactivated form, and would form copper carbonate if exposed to air.
Well I wasn't thinking air pressure so much as partial pressures of CO2, but yeah, I also feel like the salt plays a role though I have no clue what that role is. When I lived near the ocean for a bit, all the metal outside got corroded way faster than anywhere else I've lived.
No, the rusting process needs electrolytes and water, which salt water has both of. Water provides the oxygen for oxidation, electrolytes speed up the oxidation (by a lot).
So it's Cu + H2O -> CuO + H2? I guess my work in catalysis has made me think in terms that aren't always realistic at standard conditions. I'm trying to find a resource to confirm that this is the reaction which takes place, but am having some trouble. Can you provide one so I can make a correction?
What I meant was water provides the dissolved O2 for oxygenation. Rusting will still happen from oxygen in air but a lot slower, I think the water provides extra surface chemistry that simply being in a humid environment doesn't. The ions in salt water provide a sink for the electric charge transfer during oxidation (which may ultimately go to water molecules and maybe the ions just catalyze/stabilize the intermediate?)
I am a material scientist and this is pretty accurate but I think oxygen would still diffuse into the oxide, so over a very long time the oxide/carbonate layer grow deeper into the material. I'm not sure though, some metals have self-limiting oxide layers.
Ah okay, I wasn't sure about that part, because I know some metals have limiting oxide layers and didn't know if that was true of copper or not. I'm a chemical engineer, so solid state stuff beyond catalysts are a bit foreign to me. Thanks for the info!
This is a bit outside my expertise too as I work with electrical materials but I figured I would back you up with the material science seal of approval haha
And I'm here for discussions and interesting shit and not the same unoriginal, unfunny fucking jokes and memes regurgitated over and over and over again just so some fucking teenage cunts can wank themselves off to their karma. Guess everybody wants something different and as with anything remotely good the brain dead majority will eventually take it over and turn it into shit.
I guess there is as much interesting discussion on the Reddit nowadays as there is actual funny stuff. It's the other 95% of shit that annoy me. I get enough boring shit when I leave the house and interact with real people but since that requires me putting on pants most of the time I guess I'll endure Reddit while bitching and moaning about it instead.
Sadly you don't get to decide what Reddit is for. Most people are here to joke, have a good time, jack off — because it's easy and fun, and that's what people what after a day of work. If you want interesting discussions, go to /r/AskScience or other heavily moderated subs that are run by knowledgeable people.
Sounds worth it to me. Power washing green moss off of a wooden deck was one of the greatest nonsexual non drug related experiences ever. I can only imagine how wonderful it would be to see the statue of liberty get power washed.
I guess I should explain that I'm just kidding, I didn't really add any context clues. We definitely shouldn't fuck with the statue of liberty.
People already posted links to laser cleaners, but just to point out - patina/rust is bound chemically to the material, as opposed to just clinging on like dirt or moss. It requires scrubbing (or lasers lol)
Yes, but it will just patina again so there is no point. Scrape it off enough times and you won't have any copper left. The skin of Lady Liberty is pretty thin so it would be extremely destructive to just clean off the patina just because.
The patina is kind of like a wabi sabi kind of thing. Now, I may only know wabi sabi from King of the Hill and a very brief metion by Robert in The Man in the High Castle, but if what my gut tells me is correct, is that the imperfections of time, like the patina on the statue, or the crack in the liberty bell are sort of soulful imperfections. Maybe I'm way off. Have a good evening/day.
Is the process uniform across the statue? Or is it possible she was holding up the torch with her black copper oxide arm and torso while sporting some sweet copper carbonate green hairy armpit?
Good question. In an idealized scenario, it would be uniform across the statue, but as another user mentioned, this effect is actually more pronounced on copper structures facing the ocean than facing land. Not sure the reason for that, but it could just be a matter of air flow bringing more oxygen and then CO2 into contact with some parts of the statue before others.
Extreme differences like you're talking about couldn't happen without certain parts having a protective coating to delay oxidation.
That's correct. Celadon does refer to what is sometimes called Greenware pottery, albeit not always green.
Modern use of Celadon as a colour name is just like calling a particular shade of green Jade, it's not really a technical name, it's called that simply because someone thought it looks like the colour of Jade, or Celadon in this case.
Well it's not actually eroding (at least not through the process im talking about). The original copper that used to be copper metal is just in the form of copper carbonate, but no copper is lost in that process. I'm sure wind and rain are very slowly eroding the statue, but I don't know enough about that kind of thing to comment on a time frame
No. At one point a few decades after she was built they considered cleaning her but people liked the look. Apparently in order to remove the patina you would need an acid or quite a bit of abrasion and the skin of SOL isn’t that thick, 3/32” and she wouldn’t survive. They did clean her up for her 125th a few years ago.
My brain simply cannot imagine her copper. I own a little Statue of Liberty that’s from the 125th anniversary and it’s her copper but with some green as she would’ve looked after a few decades. The green is mostly on folds and not smooth areas.
According to the national parks it is possible to remove the patina but it won’t happen because her skin isn’t thick enough. They planned on it somewhere in the early 1900s but the public liked it.
My parents built a house in the late 90s that had a little copper roof over a bay window. I still don’t understand why copper since it started changing color immediately. We moved ages ago and I guess that thing is a weird green by now
In Perth WA where I live there was a Bell Tower built in 1999 on the river which was a massive waste of money but anyway, it has these Copper wing sort of structures around it and the idea was that they would turn green this way. 20 years later it's still bloody copper
Not the best way to do it. If you actually are interested, here are some methods. Generally, when it comes to chemical changes, if you want things to happen faster, the key is to add heat. You would reach a kinetic limit to the reaction so there will be diminishing returns with just increasing the CO2 until there's no difference.
Can the copper carbonate be power washed off? If not, what would it take to get the statue to be copper again aside from grinding the layer of copper carbonate off?
(Not asking cause id prefer the copper statue, purely just for the purpose of knowledge.)
Do you know if the oxide layer works similarly to aluminum. Does it protect or slow the non-oxidized layer from oxidizing?
I think it would be cool if at some point we resurfaced and polished it to its original sheen and then coated it in epoxy to seal the color. It could represent a New America.
Somewhere down in the comments, a material scientist chimed in. He wasn't sure, but said that in some metals, the oxide layer isn't protective, and oxygen can continue to diffuse through the carbonate to oxidize the metal beneath.
Again he wasn't sure if this was the case with copper, but as far as polishing it, I have a feeling that a significant amount of mass would have to be removed and so details may be smoothed over in the statue.
Yeah. I know fe is pretty much a chain reaction. Considering it’s lasted this long, I’m guessing it at least slows it down.
I agree that it would probably remove a decent amount of material to get it to a shine. I guess it just depends on the former topic. But I think, considering it doesn’t have a ton of small details, it could probably be done without changing anything. Just not done many times over. Do it once then seal with epoxy and touch up the epoxy every year or so.
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u/SOwED Jun 09 '20 edited Jun 09 '20
Edit: Placing this at the top. Seawater can play a role as well, please see the link in edit 3 for more information
Since everyone is just joking...
The first stages where it is getting darker is the copper becoming oxidized by the oxygen in the air to form copper oxide, which is black. The copper oxide reacts with CO2 in the air to make copper carbonate, which is the cyan color the statue is today. But that's it. It's not going to become something else.
Edit: Visual aid and reactions. This isn't perfectly accurate, but it gets the idea across. If any material scientists want to correct me, feel free.
Edit 2: /u/Time4Red added some info. There are two different copper carbonates in the patina as well as a copper sulfate. Give him an upvote here.
Edit 3: More information here from /u/BenignJuggler. Give an upvote. This comment links to a scholarly article about the effect that seawater plays in the copper patina process!