DIY Tin Plating for Bus Bars

Copper bus bars are commonly used instead of wire for carrying high currents. [Dane] needed some bus bars for a project, but he was worried about corrosion. His solution was tin electroplating the bus bars to lower the risk of corrosion while keeping the conductivity high.

The process requires only two chemicals: hydrochloric acid and tin. The electrolyte solution is made by dissolving tin into the acid. Then the bus bar is placed in a diluted solution and a 1 A current is run through it. The result is a fine coating of tin on the copper, which will not corrode in water.

[Dane] mentions that he’d like to try the process with silver solder in the future, since it is easier to find than tin. He also wants to find a way to measure the amount of tin deposited onto the bus bars. This process could be helpful for anyone who needs some corrosion resistant high current conductors.

Check out a video of the plating process after the break.

Comments

  1. firefightergeek says:

    This may be a dumb question, but why not just carefully weigh the bar before and after coating?

  2. repurposer says:

    An accurate balance would be a good way to measure the total mass of tin. Divide by density to get volume then divide by surface area to get average thickness.

    • Leithoa says:

      That’s the trouble though. An accurate balance isn’t cheap. Commercial electroplating is only .175 microns thick so assuming he’s in the same ball park and that the dimensions of the bus(based on the sharpie) are 10x1x0.5 inches he’s only putting on 0.021g of tin. Obviously he can go thicker since cost isn’t really an issue at this scale but an accurate balance out to 3 decimale places will run into the multiple hundreds of dollars, 4 and 5 decimals, well into the thousands.
      There are scales that read to 0.01g for around a hundred bucks but that last decimal is a bit of a fairy tale.
      Another option is titrating the amount of tin left in the electrolyte and assuming that there is a finite amount of tin it is a very accurate procedure. But that still requires dedicated equipment.

      • repurposer says:

        I guess he could just do the math on the data he already has. I work out that he’s done 14.4 micrometer average thickness. 1.16 A for 30 minutes = 1.3031E22 electrons. Sn(II) + 2e- -> Sn(0), so 6.515E21 atoms were deposited, or 1.28 g tin. Assuming white tin, not gray was deposited, this gives 1.44E-3 cm covering the 120 cm^2 surface. Course I’m a bit hung over. Could be off an order of magnitude here or there.

      • Dax says:

        The solution is to use a mechanical lever on an ordinary kitchen scale to increase the apparent weight of the bar.

  3. markey1979 says:

    Wow, I knew this was easy, but that looked really easy.

    Did you follow the link to his website? At the end where he shows us the finished project, I want to know what that is for!!!!

    …..It look like an array of IGBT’s to drive a 3-phase motor. The setup looks serious.

    …..I mean Water colled???

    I want to know more about that project…..

  4. Jeremy says:

    Pure tin plating on copper is almost guaranteed to grow whiskers. This is especially true if there’s any major thermal cycling of your device. You don’t have any microelectronics exposed to the same air as this bus bar do you? I’d suggest separating any small-pitch IC packages or densely poplated PCBs with another layer of project box just to be safe.

  5. Whatnot says:

    Only 3.1 volts? Curious, I’ve seen other electroplating experiments but they most often used 12V.
    3V at 1A is very doable.

    • Montaray Jack says:

      It’s not the volts, but the charge. It also varies with surface area being plated. The valency number of the ion being deposited or removed also comes into play. Roughly 96,500 coulomb (Ampere/second) will deposit one gram equivalent weight of metal. Strangely enough, this is Faraday’s Constant.
      http://en.wikipedia.org/wiki/Faraday%27s_laws_of_electrolysis

      Also the Metal Finishing Guidebook, sort of like the Machinists Handbook for platers has more information.

  6. Whatnot says:

    BTW, I think RoH solder is tin/silver or tin/copper? But it has normally a rosin core though, and I’m not sure how it would work even when you heat it to remove the rosin first.

  7. Chris C. says:

    Looks good to me. I wonder what the assembly is for too.

    A tip for anyone wanting to take a shortcut – the “tin sheet” at hobby stores is not solid tin. It only has a thin tin plating itself and is useless for this.

    • Dane says:

      The assembly is a giant 3 phase motor controller, that I haven’t quite finished yet. When it works i’ll try documenting it up.

      Consequently that beast of IGBTs could also function as a giant 3 phase dubstep power-amplifier now that i think about it.

  8. NorthernDIY says:

    While I can appreciate the effort, wouldn’t skim coating it with some solder and a propane torch be easier?

    • Whatnot says:

      Normal solder has lead, you don’t want to be touching lead all the time.
      But leadfree (or pure silver) solder would work since it’s copper and solder is designed for copper, but it would require a whole lot more of it since the layer would not be as nice and thin as electroplating.

      Still a good point though

    • Dane says:

      Hey, yeah, solder coating would be possible but rather difficult. Even with lead free solder, its a metric boatload of heat to cook up a 12″ long bus-bar at a constant temp and get any resemblance of even plating. Its easier to do on pcb’s as there’s less of a thermal loading.

  9. tz2026 says:

    Stannous Chloride or Sulfate – I forget which – will tin-plate copper boards and would probably work for that, since tin is above Copper in the replacement series. Any copper ( you can do it with pennies) will be plated But it would be harder to control the thickness.

  10. dementia says:

    Anyone know where to get strips or sheets of beryllium nickel for making custom contacts? Something gold plated would also be helpful.

    I need to make some electrical contacts and embed or insert them into plastic.

    TIA!

  11. Montaray Jack says:

    As for mesuring the thickness of the plating, a really, really sensitive dial indicator . At the tool & die I used to work at I would probably use a AA lab grade granite surface plate, some AA grade Jo Blocks and a CEJ Johansson Mikrokator 510E-6 Indicator .00001″
    We had a couple of those around the shop. PITA to use, temperature of the room and vibration really comes into play down at those scales, plus you have to be really accurate in pushing the part you’re mesuring under the point. It takes a delicate touch. You would have to set it up as a comparator, zero it out before you did the plating and then re-read it after and divide by 2 to give you the thickness.

    with the setup like you showed in the video, you’re probably have slightly thicker in the middle side facing the anode, thiner at the edges and thinner on the opposite side also tapering toward the edges.

    Probably easier to calculate it using Faraday’s laws of electrolysis than to actually measure it.

    • Montaray Jack says:

      BTW the plating pros use fluorescence x-ray measuring,Magnetic induction,Eddy current,Coulometric or Beta ray backscatter to mesure plating thicknesses.
      http://www.qualitydigest.com/aug04/articles/03_article.shtml

    • Montaray Jack says:

      At 1 amp somewhere around 1.1 g per hour is deposited.
      I was curious, so some quick off the cuff calculation.

      m=Q/F*M/V

      Really I’m sort of misusing this equation, Faraday was really measuring the liberation on the anode side, not necessarily the deposition on the cathode side. Potentially, the liberated Sn ions could end up in solution, especially if the solution wasn’t saturated already.

      Another way to measure the deposition of the plating could be by mass, if you have a balance. Mesure the mass before, and after. It doesnt tell you squat about local thickness of the plating at any given point, but you would atleast know the total amount.

    • Montaray Jack says:

      @ silverfishes
      Those are Induction or Eddy current probes.
      Precision Plating here in Chicago uses Xray fluorescence, but I’m sure they also have other equipment. The right tool for the right job. I’ve no idea what Belmont Plating uses, but we’ve used both companies (and others) back in the day, Belmont was closer, so we used them more often.
      PPC doesn’t do chrome or black oxide anymore, so if we needed hard chrome plating it wasn’t through them.
      Sometimes it came down to who was willing to do and certify the milspec stuff.

      I wouldn’t use either company to restore a chrome bumper on a classic car, though. Not their speciality, but lucily in Chicago is argueably one of the best platers for custom car and mortorcycle parts on the planet. I don’t recall his companies name right now. Very labor intensive to get a cosmetically perfect restoration.

      As for the crazy accurate tools, well that was the kind of shop we had. I think we had only 2 toolroom grade (“B” grade) surface plates in the shop & those were the really big ones, everything else was A or AA. Indicators, a Starrett Last Word was my daily driver for machine setup, rugged & hard to break, but almost as often I used a .0005″ Interapid, the 0.0001″ Interapid would come out for fussy work, and the Mirrokators when we were making gages +/- 15 millionths or less. They’re a real pain because they only have 0.0008 travel.
      We had another kind of indicator/comparator that used a box with a analog Galvonmeter and a probe. Sort of a ’70s precurser to the probes on CMMs. I dont recall who made it. Really sensitive though, down to 5 millonths.
      One of our AA Jo block sets was only ever used to calibrate the other sets, so it was used once a year. Cotton glove time. The daily driver was a big set of wornout carbide Jo blocks, pretty much unusable without the real numbers on the cert sheet with any accuracy. Plenty of Cadalac Gages scattered around the shop, so Jo blocks weren’t necessarily needed.

  12. hardcorefs says:

    The plating will not be even.

    You need to surround the item being plated , otherwise the plating is the thickest on the same side facing the other conductor.

    Plus now he has a ‘battery’ (two dissimilar metals).

    Would have been better to just ‘brasso’ and varnish.

  13. wowme@wtf.com says:

    the background noise! Really?

  14. 556NATO says:

    Why couldn’t he have just purchased a chemical tin plating kit… The results from this aren’t going to be great, and he would have saved a lot of time…

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 91,410 other followers