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 Electroplating, platinum
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| EEYORE |
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Registered Member #99
Joined: Thu Feb 09 2006, 12:10PM
Location:
Posts: 579
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Hello all, I just acquired some nice chloroplatinic acid from Peter here (Thanks much!). I have been trying to plate a few things before I go for the electrodes for a fuel cell.
Im having some trouble. I can achieve a thick shiny black smudge like coating that really REALLY sets off H202, but this nice thick coating comes right off, leaving not much of a coating at all. So far ive tried to plate some steel washers, and some galvanized steel( i think, its highly magnetic and deffinately galvanized). Nothing sticks. I put a washer in some hot sulfuric acid to see if it would eat away the surface, which it looks like it did(left a very dull finish on a shiny steel washer).Came right off after platinum plating. I then tried the galvanized sheet steel. First I washed it in water and then wiped with acetone. Plated on, but came off. I then sanded it down REALLY well, and that kept a bit more platinum on, but now has rusted over REALLY bad! I also notice that it looks like platinum is falling out of solution and forming platinum black, a very finely divided platinum metal. This is no use for the method I wish to use it.
Perhaps steel is just not possible?Should I try to nickel plate it first?HGold plate?Silver plate?I dont want to waste anymore of this stuff, its hard to come by!Already used a good bit...
Thanks guys!
Matt |
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| Marko |
 Tue Oct 17 2006, 12:51PM |
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Registered Member #89
Joined: Thu Feb 09 2006, 08:40AM
Location: Zadar, Croatia
Posts: 2586
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I always wanted to plate PCB's with silver (or gold) but I don't know if it's possible once t's etched. I can't electroplate it, so I would need some other method for depositing silver on copper.
Regarding your steel, I once tried plating with ZnCl2 (homemade  ) wich worked great for copper, brass and iron, a bit worse for various steels but layer came of insantly from alluminium.
Didn't play with it a lot as I grew tired of bllowing the chlorine out of window.
Be sure to poliish the piece by hand before plaitng, with steel wool, acids and stuff leave too much 'dirt' behind!
I would keep your platinum for TC gap electrodes. YOu could also try a PCB but I don't know ow could you etch it anymore.. |
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| Eric |
| Tue Oct 17 2006, 03:56PM |
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Registered Member #69
Joined: Thu Feb 09 2006, 01:42AM
Location:
Posts: 116
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When the coating is dark and wipes off easily it is being deposited as a finely divided mud which may also slough off in the bath. A current density that is way too high can cause this. Chemical contamination in the bath can cause this, ph being off, etc.
With platinum you might also be getting this from immersion deposits. These are caused because platinum is much nobler than the substrates you're plating on to and gets spontaneously reduced to metallic form, usually not as you want. This problem is minimized if you use the most noble or passive metals to start with like gold, silver or maybe copper. I think iron would be bad and anything with zinc on it (galvanized stuff) would be REALLY bad. Zinc dust is actually used to precipitate gold, platinum metals out of solution.
Somebody else wrote about plating platinum on nichrome, which forms a very passive surface. You might try that just to make sure your solution still works. Good luck, sounds like fun. |
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| EEYORE |
| Wed Oct 18 2006, 12:20AM |
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Registered Member #99
Joined: Thu Feb 09 2006, 12:10PM
Location:
Posts: 579
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I thought it might be the zinc or steel causing the Pt. metal to fall out of solution. Good thing is, Pt. black is useful, just not easily used. Its all settled in the bottom of the dilute mixture I made, I may filter it out and see what I can do with it. Any idea what the chloroplatinic acid solution is after the Pt. has left it?
I got some silver chloride on ebay, 25g of it. Might this plate some 316 stainless, and then work to plate platinum onto?
Matt |
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| Eric |
| Wed Oct 18 2006, 12:51AM |
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Registered Member #69
Joined: Thu Feb 09 2006, 01:42AM
Location:
Posts: 116
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You could try plating the 316 directly with platinum. It should have a very passive surface like nichrome does. Generally, stainless is hard to plate because it is so passive, plated metal doesn't adhere well. You might also try dialing back on the voltage/current in case it was too high before. I'm wondering if you might have depleted your solution, it couldn't have had much platinum in it to start with.
As far as the silver goes, I was watching that same auction! Forgot about it... Oh well, here's what I was going to try with it. |
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| EEYORE |
| Wed Oct 18 2006, 01:32AM |
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Registered Member #99
Joined: Thu Feb 09 2006, 12:10PM
Location:
Posts: 579
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Eric wrote ... You could try plating the 316 directly with platinum. It should have a very passive surface like nichrome does. Generally, stainless is hard to plate because it is so passive, plated metal doesn't adhere well. You might also try dialing back on the voltage/current in case it was too high before. I'm wondering if you might have depleted your solution, it couldn't have had much platinum in it to start with. As far as the silver goes, I was watching that same auction! Forgot about it... Oh well, here's what I was going to try with it.
That sounds good about the 316, I will try it out before I try silver plating it. No worries with the Pt. Acid, I had a bottle of 10mL 10% to begin with( 500mgPt.), and I would make diluted solutions with it. I still have about 6mL of the acid left to use. If I need more, I found a source for 25$ per gram of it.
Matt
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| Chris |
| Thu Oct 19 2006, 05:11AM |
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Registered Member #8
Joined: Wed Feb 01 2006, 10:34PM
Location: Harlowton, MT, United States
Posts: 212
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Electroplated platinum tends to have enormous tensile stress within the deposit, escpecially if it is thick. It can easily break and peel off. This can be allieviated to some degree by using a lower plating current. Stainless might not be the best base metal either - I'm not sure about that though. Perhaps try an undercoat of nickel or copper or something. Platinum plating is just an inherently tricky thing, and may take some trial and error, but you can recycle the stuff over and over (with some effort) if neccessary.
You could also try plating from ammonium chloroplatinate (another common platinum plating salt). This can be accomplished by simply reacting the chloroplatinic acid with ammonium chloride. To get chloroplatinic acid back, just heat the ammonium chloroplatinate to decomposition then dissolve the Pt powder back in aqua regia (yielding chloroplatinous acid after some additional treatments with HCl), then chlorinate further with chlorinated water. I will describe in more detail below.
And don't worry, you haven't really wasted any. It can be recovered if you wash the failures with sulfuric acid or nitric acid to dissolve the other metals, then filter and treat the platinum black as I described above with aqua regia. Then boil it dry a few more times with HCl to convert the portion of nitrosoplatinic chloride to chloroplatinous acid. Treat chloroplatinous acid with chlorinated water to yield chloroplatinic acid, then boil dry.
If you don't have a source of nitric acid I may be able to help you out with that, or you could distill your own if you have glassware. |
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| EEYORE |
| Thu Oct 19 2006, 07:16PM |
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Registered Member #99
Joined: Thu Feb 09 2006, 12:10PM
Location:
Posts: 579
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Chris wrote ...
Electroplated platinum tends to have enormous tensile stress within the deposit, escpecially if it is thick. It can easily break and peel off. This can be allieviated to some degree by using a lower plating current. Stainless might not be the best base metal either - I'm not sure about that though. Perhaps try an undercoat of nickel or copper or something. Platinum plating is just an inherently tricky thing, and may take some trial and error, but you can recycle the stuff over and over (with some effort) if neccessary.
You could also try plating from ammonium chloroplatinate (another common platinum plating salt). This can be accomplished by simply reacting the chloroplatinic acid with ammonium chloride. To get chloroplatinic acid back, just heat the ammonium chloroplatinate to decomposition then dissolve the Pt powder back in aqua regia (yielding chloroplatinous acid after some additional treatments with HCl), then chlorinate further with chlorinated water. I will describe in more detail below.
And don't worry, you haven't really wasted any. It can be recovered if you wash the failures with sulfuric acid or nitric acid to dissolve the other metals, then filter and treat the platinum black as I described above with aqua regia. Then boil it dry a few more times with HCl to convert the portion of nitrosoplatinic chloride to chloroplatinous acid. Treat chloroplatinous acid with chlorinated water to yield chloroplatinic acid, then boil dry.
If you don't have a source of nitric acid I may be able to help you out with that, or you could distill your own if you have glassware.
I may switch to copper sheeting as the electrode. I found a site showing silver chloride being used along with salt and cream of tarter. It is all crushed up and then rubbed on to metal sheeting. Copper is one of the first metals listed as being very easy to plate via this method. I imagine it will only plate a very thin layer of silver, but that ought to be enough. I did put some platinic acid on a silver coin...Damn, now I have a black spot that will catalyse peroxide and will not come off!It appears that silver is very good for platinum plating. Id love to use the 316 mesh, but I dont think its possible to plate silver onto it via this method. I read about silver plating, and it sounds really hard to do!I seem to be going in a circle...bleh  Maybe I ought to just try plating a piece of silver with Pt. then using that to catalyse NaBH4 and collect the hydrogen gas...Alas...
Matt |
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| Chris |
| Thu Oct 26 2006, 04:08PM |
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Registered Member #8
Joined: Wed Feb 01 2006, 10:34PM
Location: Harlowton, MT, United States
Posts: 212
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Can't you just plate the platinum right onto your copper mesh from chloroplatinic acid or ammonium chloroplatinate?
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| EEYORE |
| Thu Oct 26 2006, 06:03PM |
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Registered Member #99
Joined: Thu Feb 09 2006, 12:10PM
Location:
Posts: 579
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Chris wrote ...
Can't you just plate the platinum right onto your copper mesh from chloroplatinic acid or ammonium chloroplatinate?
Nope, the acid seems to react somehow with the copper rather than plate to it. Silver works really well though, so I will be attempting to plate with silver, then platinum.
Matt |
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| ... |
| Thu Oct 26 2006, 06:14PM |
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Registered Member #56
Joined: Wed Feb 08 2006, 11:02PM
Location: Southern Califorina, USA
Posts: 2118
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Could you give nichrome a try? I remember seing a site that used it, and it seemed to work...
Seems a heck of a lot easier to buy a few ft^2 of nichrome mesh from McMaster (I need to make an order in the somewhat near future for my laser diodes) than to silver plate copper then platinum plate it...
check out my website! |
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| Eric |
| Thu Oct 26 2006, 06:20PM |
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Registered Member #69
Joined: Thu Feb 09 2006, 01:42AM
Location:
Posts: 116
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Silver plating could be fun though... you could try the method described in the patent I posted above. See page 5 Example #1. You've got the silver chloride already. |
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| Carbon_Rod |
| Thu Oct 26 2006, 09:46PM |
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Registered Member #65
Joined: Thu Feb 09 2006, 12:43AM
Location:
Posts: 504
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Eric is right, Iron can be a really bad surface by itself.
Most plating generally follows the pattern:
Copper, Nickel, and then Chrome or whatever.
However, to flame plate with platinum deposits is easy. Dip, flame, and repeat as needed.
Cheers,
"As you go through life, make this your goal: Keep your eye on the doughnut and not on the hole." (?)
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| EEYORE |
| Fri Oct 27 2006, 01:16AM |
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Registered Member #99
Joined: Thu Feb 09 2006, 12:10PM
Location:
Posts: 579
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Carbon_Rod wrote ...
Eric is right, Iron can be a really bad surface by itself.
Most plating generally follows the pattern:
Copper, Nickel, and then Chrome or whatever.
However, to flame plate with platinum deposits is easy. Dip, flame, and repeat as needed.
Cheers,
I like this idea of flame plating...Could you elaborate on it some more?How might I go about flame plating something with some platinic acid?
Thanks!
Matt |
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| Carbon_Rod |
| Sat Oct 28 2006, 06:01PM |
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Registered Member #65
Joined: Thu Feb 09 2006, 12:43AM
Location:
Posts: 504
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"Dissolve Chloroplatinic acid in 50/50 Et2O/EtOH.Dip the Pyrex in the solution and flame in a bunsen flame.Platinum will be deposited as a mirror finish." (Penn ???)
"The original formula was 0.2 gm of the acid in 5ml each of ETOH AND Et2O.Add
4-5 drops of turpentine.Dip and flame.The book I got this from was published
in 1960 and so may refer to vegetable turpentine.I have used it successfuly
without turps but the solvent evaporates very quickly.I assume the turps will
slow this down.You can dip and flame several times to build a thicker Pt
layer." (Dave ???)
Cheers,
"As you go through life, make this your goal: Keep your eye on the doughnut and not on the hole." (?)
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