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Author Topic: Electrolysis! Or how I'm getting chrome off of my goggles with minimum effort.  (Read 3561 times)
Matthias Gladstone
Zeppelin Admiral
******
United Kingdom United Kingdom


Call me Ishmael


« on: May 19, 2009, 06:29:38 pm »

Now I don't normally do projects with heavier stuff like metals and leather, due to lack of tooling, but I like to get stuck in when I can.
Another forum member recently posted a pair of goggles which had started off as a cheap pair of flying goggles. He made the rather useful discovery that under the horrible chrome finish, it was all brass, and from this, he ground it off (IIRC).
Capitalising on this, and lacking grinders/the effort, i'm using electrolysis to remove the plate. Using the goggles frame as the positive terminal (anode?) I've been steadily passing a current and a 12v EMF though from a small liquid battery:
Spoiler (click to show/hide)
It's a slow process, and i'll need to recharge the battery before I can continue, but eventually i'll end up with some nice copper framed goggles (theres a layer between the brass and chrome). As theres brass underneath, all i'll need to do is heat it in a strong flame so it allows with the zince beneath Smiley
Electrolyte is strong brine, beware as chlorine is given off   Tongue
If anyone's got any advice, that would be handy.
Cheers,
-Matt
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sidecar_jon
Snr. Officer
****


« Reply #1 on: May 19, 2009, 06:54:42 pm »

I've done it with heap Smiths pocket watches, i used handful of salt in water and a car battery charger...slides right off fast, though i wouldn't recommend putting hands in the running solution!
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evand
Gunner
**
United States United States


« Reply #2 on: June 01, 2009, 04:58:44 am »

Copper sulfate makes a good electrolyte that doesn't release nasty toxins.  It's available at hardware stores as septic system root killer.  And a generic 12V (or other...  12V is fine, but you can get by with anything from about 5V to 18V) wall wart power supply isn't too hard to come by, and is more convenient than a battery.  Can't wait to see how they come out Smiley
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Matthias Gladstone
Zeppelin Admiral
******
United Kingdom United Kingdom


Call me Ishmael


« Reply #3 on: June 01, 2009, 07:21:45 am »

Cheers Smiley
I've aquired the use of a college power pack, and i'm taking them in next week. We're just going to stick it in a fume cupboard and leave it mafipulating for an hour or two.
-Matt
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rovingjack
Zeppelin Admiral
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United States United States



WWW
« Reply #4 on: June 02, 2009, 03:45:47 am »

don't heat it to get rid of the copper. your could probably get down to the brass by simply switching solution over to either a vinegar with current or if memory serves me pure lemon juice will take copper off without a current at all. and what I like about the later is that afterwards any ferrous metal put into the solution will take on a copper coat.
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Matthias Gladstone
Zeppelin Admiral
******
United Kingdom United Kingdom


Call me Ishmael


« Reply #5 on: June 02, 2009, 10:45:42 am »

Cheers  Smiley I love alchemy Grin

When you say pure leom juice, can I use the stuff from concentrate you buy in the supermarket or am I going to have to squeeze loads of lemons?
-Matt
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sidecar_jon
Snr. Officer
****


« Reply #6 on: June 02, 2009, 02:12:27 pm »

I used salt solution to get rid of chrome and electricity as i said, to clean the brass/copper, you can use lemon juice (yep Jiff or any lemon juice is fine, though maybe not lemon squash!) or plain old vinegar.
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Lord.Escher
Deck Hand
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United States United States



WWW
« Reply #7 on: June 09, 2009, 08:53:53 am »

So salt-water will strip the chrome and leave the copper finish behind? Is that right?

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sidecar_jon
Snr. Officer
****


« Reply #8 on: June 09, 2009, 01:56:19 pm »

So salt-water will strip the chrome and leave the copper finish behind? Is that right?



Well its a relative thing but yes, if you leave it in the bubbling solution for days the copper will be eaten too, your just copper plating the electrode opposite, but the chrome goes first.
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Matthias Gladstone
Zeppelin Admiral
******
United Kingdom United Kingdom


Call me Ishmael


« Reply #9 on: June 09, 2009, 09:40:16 pm »

Well, I got the chance to do it today. No pics yet as the goggles are still at college, but the whole process was rather interesting.
It started off looking safe enough - clear water, nice bubbling at the negative elctrode but after about 1/2 an hour the water was a slimy greeny yellow colour, with copper and chrome floating on the surface, black chromate salts on the bottom and what I was cheerfully informed was sodium hydroxide floating about in lumps within.
Despite this, with the encouragement of my physics teacher and class, we continued and were rewarded with a pair of shiny, copper goggles covered in a toxic looking green and yellow sludge, which I duly washed off, dying my hands green in the process. I washed very thouroughly, and luckily my hands are now their usual pinky colour.
Although the goggles' frame was cleaned perfectly and otherwise unaffected, the steel clips on the sides were strangely corroded in the places where they had touched the brass clips. Most of the steel was sound, but where the brass had been touched it had eaten through as if it had been attacked with a very strong acid. The brass clips themselves were even worse - one was just about ok, but the other had been stripped of it's copper and was nothing but a spindly zinc matrix.
In summary, it was a great mad science experiment that I strongly recomend. Just be very careful and be aware some of the products in the water may be toxic. I now have "alchemist" to add to my credentials.
-Matt
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evand
Gunner
**
United States United States


« Reply #10 on: June 09, 2009, 10:23:17 pm »

Although the goggles' frame was cleaned perfectly and otherwise unaffected, the steel clips on the sides were strangely corroded in the places where they had touched the brass clips. Most of the steel was sound, but where the brass had been touched it had eaten through as if it had been attacked with a very strong acid. The brass clips themselves were even worse - one was just about ok, but the other had been stripped of it's copper and was nothing but a spindly zinc matrix.


Sounds very cool.  Do you have pictures?

The corrosion of the steel is galvanic corrsion.  Steel is anodic to brass and copper; copper is anodic to brass.  When two dissimilar metals are in contact with a common electrolyte (ie salt) solution, a galvanic cell (battery) is formed.  Short it out, by letting the two metals touch or otherwise make electrical contact, and the anode will corrode, potentially quite rapidly.
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Matthias Gladstone
Zeppelin Admiral
******
United Kingdom United Kingdom


Call me Ishmael


« Reply #11 on: June 09, 2009, 10:47:59 pm »

Indeed; I remember when I used to help out on my friend's yacht that sea going vessels suffer from the same thing. There were lumps of zinc nailed to the bottom of the boat, to corrode in a sacrificial manner and save the rest of the vessel.
The speed of it surpirsed me; but I suppose we had a very strong saline electrolyte, and a strong, constant current passing through and I guess it was somewhat inevitable. I'm just a little miffed as i'm going to have to make new clips now.
As I said, I don't have pics as the goggles are still at college, but I will snap some pics tommorow. The fun continues as we're flying our indoor zeppelin as well.
cheers,
-Matt
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Matthias Gladstone
Zeppelin Admiral
******
United Kingdom United Kingdom


Call me Ishmael


« Reply #12 on: June 10, 2009, 06:27:16 pm »

Victory!:

Just need to do the lemon juice on the copper and soak the chemicals out of the leather padding. Several water baths over the next few days I feel...
-Matt
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Matthias Gladstone
Zeppelin Admiral
******
United Kingdom United Kingdom


Call me Ishmael


« Reply #13 on: June 14, 2009, 06:33:25 pm »

An done:

I decided to leave the copper on there, it's something a bit different and the layer is so thin it will wear off naturally quite quickly. Also, the brass has a slight green tinge and isn't brilliant.
The only other thing I plan to do is make the lenses green (any ideas?) and use myke amend's tutorial to make the faux leather brown.
-Matt
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Phineas Lamar Alexander
Snr. Officer
****
United States United States



« Reply #14 on: June 27, 2009, 04:26:02 pm »

Those look fantastic!!!!
I have got to try this with some silver plated items I acquired at a thrift store.
If they are electro plate on copper then I get copper goodies!!!!!
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Jumjum
Deck Hand
*
Sweden Sweden



« Reply #15 on: May 07, 2012, 07:46:04 pm »

You have all made my Day!! I  search Google how to remove chrome from brass, some suggested to use strong acids (a little bit dangerous and hard to get my hands on) , some Acetone (I'm gonna remove chrome not nail polish!)...but nobody could show the final finish!

So now can i start to clean up some flee market treasures (don´t like to grind for hours Shocked )
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I love the overworked brass screws and things like that on old technical instruments, it´s has no function beside to be beautifully!
MakerMike
Gunner
**
United States United States

MakerMike
« Reply #16 on: June 12, 2012, 09:27:20 pm »

To add my two cents here, since I am a professional (al)chemist, and an electrochemist to boot...

Under the conditions that you're working, you're oxidizing the chromium (and the metals in the underlying brass) and you're electrolyzing water at the same time.  That's obvious at the cathode (negative electrode) as you see bubbles forming (hydrogen, by the way), but it's happening to some extent at the anode (positive electrode, the goggles).  It may not be obvious because it might be happening too slowly to form bubbles, but it also forms acid.  So the corrosion of the steel clips could be indeed attack of an acid.  Also, as another poster said, it could be galvanic corrosion at the junction of the brass and steel.  The green stuff in your bath is likely copper chloride.  Not too poisonous unless you're a fungus.  Wear gloves anyways.

In any case, this is a messy process with all the different metals in there and the high voltage you're applying.  Still, we're not looking for a mirror finish here, but something that looks somewhat old and worn, so have at it!  Good job!
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