Metal finishing Q&As since 1989
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What is this sludge? (an actual environmentally concerned question!)
2007
I am early in the lengthy process of copper plating a lot of small parts that require it, and the other night after building my plating rig, I had some time to kill and decided to try it out with one of the dozens of home-brew methods I've accumulated over the years.
This method was:
Anode : 12" of 60-80 cleaned, coiled ~99.99% copper wire strands
Cathode : cleaned 2001 state quarter (North Carolina, if you were curious)
Solution : 300ml distilled, room-temp water with 1g of a 50%/50% KCl/NaCl mix
Container: Just your basic polypropylene bowl.
These were attached with steel alligator clips to, initially, four 1.5V AAA batteries in series, and 6 hours later, (when I got impatient,) two 6V batteries in series. (Note: Being aware of the possibility of chlorine gas production above 6V, let me mention that my work desk has an appropriate venting system with an air scrubber)
Well, my first clue something wasn't right was the lack of any actual plating. The solution became a dark brownish green within 5 minutes, and after half an hour, lots of sediment of the same color began to float on top. By the end of the experiment, a layer of the sediment floated on top, and much more remained suspended in the bottom third of the solution. Elapse 2 days, (yes, I kept it) and it's still suspended in exactly the same spot, while the top 2/3 is clear water.
Actual plating was painfully slow (took 12 hours),nearly consumed the copper wire (which I assume is from the length of time) and the quarter is somewhat copper colored, albeit a dark copper color. The copper can't be rubbed or scraped off by any method I tried, so I know it's actually plated. It's actually kind of nice looking, but I know it's not correct.
My question is two part. First, and most importantly, what is this sludge in the solution? I'm guessing it's due to the strange recipe, but I'd really like to know what it actually is. I haven't dumped it because I do consider myself to be environmentally conscious, and while my chemistry skills aren't world-class, but my sense of responsibility for what happens AFTER the experiment is.
Second, What, if anything, did I screw up? Or is this just a crappy method :) I must say that it did have the fun side effect of allowing me to capture some hydrogen and oxygen gas samples to play with (carefully, of course), but I was really hoping to end up with a shiny quarter.
Many thanks if this is deemed worthy of a reply. It's great to see such notable names in this industry taking their valuable time to help kids with science projects. Your incredible knowledge and willingness to give it freely is a wonderful thing for these kids. The world would truly be a better place of more people like you existed. I only wish the Internet had evolved to what it is while I was still in school. :)
Definitely keep pushing the environmental and safety requirements of this science to the readers. It's never too early to learn proper disposal and handling, even if you're a 5-year old working with vinegar
[in bulk on
eBay or
Amazon] and lemon juice. I can't stand when I see an article about a small-town municipal water supply contaminated by some idiot dumping their toxic waste in a sewer.
My philosophy with chemistry has always been "Treat the harmless stuff as if it were H2SO4, and the dangerous stuff as if it were a flaky thermonuclear device. And no matter what happens, clean it up." Wish more people did that.
Many thanks in advance for your time.
Artist/Hobbyist - Lenoir, North Carolina
Basically, yes, crappy method. See "Electroplating: How It Works" on this website at
www.finishing.com/faqs/plating.shtml
which will tell you in great detail how to plate copper on a quarter.
James Totter, CEF
- Tallahassee, Florida
2007
2007
Thanks for your reply, however, it seems you overlooked the first part of my question. :) The second part, that the method was crappy, I think was a given. I really need someone's best guess on what the sludge could be, as I really don't want to assume it's harmless and dump it somewhere. I'm no slouch on chemistry, but I can't figure out what this by-product is. I've removed a large amount of the copper by immersion plating with
steel wool [on
eBay or
Amazon], but I'd really like to know what I'm dealing with, so if it needs any further treatment before disposal, I can do it.
On a different subject, since my original letter, I'm happy to report I was able to plate reasonably durable test pieces with tin, copper, zinc, brass, silver, antimony, and even some homemade pewter. I did so by developing a relatively simple variation of the home-plating solution recommended on finishing.com:
70% distilled water
20% vinegar
5% of a dilute mix of Sulfamic & Hydroxyacetic acids. (two of three main ingredients in spray-on wheel cleaners).
3% of 50-70% Ethyl alcohol
2% NaCl pre-dissolved in water/vinegar mix.
1.2 - 2.0v DC
Zinc anode
Cathodes (one for each) Silver ring, gold ring, brass size #14 screw, sliver from pewter, copper ingots,
Lukewarm to Room Temp. water
Time: 10-30 mins.
This solution seems to be much cleaner and faster than the other methods I've found, and works faster and better than simply vinegar/salt/water. It apparently would let a hobbyist attempt to plate some more desirable metals without using any dangerous cyanide, tri/hexavalent chrome or any other dangerous chemicals.
The result is actually pretty good. Assuming a clean cathode, it's bright, and so durable, removal requires sanding, strong acids or melting, It also leaves no visible residue in the solution. It's obviously not as good as a professional plating shop could do, since they'd use better chemicals, layer multiple metals and have that great thing called experience :)
- Lenoir, North Carolina
2007
Hi Robert,
You might not be getting answers to your question because of the (quite justifiable) fear that if anyone offers you an answer and it turns out they are wrong any bad consequences might rebound onto them somehow.
A long long time ago there was a similar letter with some of the most applicable advice I think you'll find; chat up a local high school chemistry teacher and offer to buy pizzas for the class if they'll figure out what it is for you and what would have to be done to neutralize it.
I don't know whether or not you'll be successful, but at least it would be a relatively cheap way to find out what it is you've got if it does work!
Good luck!
Compton, California, USA
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