Electroplating copper --> graphite - Page 1
Forum section: electronics / projects

author: DTJ
author_rank: Super Contributor
timestamp: June 07, 2018, 11:45:42 am
content: Anyone played with this before?I'm trying to electroplate some copper onto some pure (99%+ reagent grade) graphite rods.As far as I can work out it should work ok, but......This is what I've tried.Copper Sulphate solution 12g/250ml distilled water.Copper bus bar as the anodeGraphite rod (1/4" diameter) as the cathode. Edit: immersed rod depth is about 1cm so area is around 2cm^2With 3V DC applied the current was around 30mA. The deposition is slow and does not bond well to the graphite. The deposited film is a dull matte finish and rubs away easily.With 6V DC applied the current increased and the deposition rate increased accordingly but it tended to fuzz up on the graphite. It was maybe 1mm thick, dull and easily brushed away.The deposits were thickest on the side of the rod facing the anode bar which makes sense. Maybe a cylindrical anode would help that aspect.The copper sulphate is from the hardware store. It's a nice blue and 'looks' pure if that means anything but it could contain impurities. It dissolves ok and leaves no sediment. It's this stuff:http://www.manutec.com.au/default.asp?pageid=5&template=PRODUCTCAT&catid=30&catalogue=6&prodid=MTO0533Has anyone any words of wisdom they can share? I was hoping for a bright solderable finish. Thanks.

author: larsdenmark
author_rank: Regular Contributor
timestamp: June 07, 2018, 12:22:27 pm
content: Maybe you are not using enough CuSO4.The solubility of CuSO4 in water is 32 g per 100 ml.Here is a small article that shows how it can be done:"An easy and practical way to solder copper wires on graphite"http://digicoll.library.wisc.edu/cgi-bin/JCE/JCE-idx?type=article&did=JCE.JCE07005.i0040&id=JCE.JCE07005&isize=MThe author is using potassium chromate in addition to copper sulphate. I would guess that it is difficult obtain potassium chromate.Note that copper sulphate and chromate are poisonous and heavy metals and not only should one take care when handling them, but also when disposing of any used material.

author: David Hess
author_rank: Super Contributor
timestamp: June 07, 2018, 01:26:35 pm
content: Graphite rods plated with copper used to be commonly available for arc lamp applications so obviously it is possible to do. The copper finish I remember was smooth and hard.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: June 07, 2018, 01:36:52 pm
content: I'm not sure the concentration of copper in solution has such a drastic influence on quality, apart of course from speed. Current and voltage should be set to avoid water electrolysis on the surface too. Are the rods raw or polished ?

author: IconicPCB
author_rank: Super Contributor
timestamp: June 07, 2018, 02:06:15 pm
content: I have used graphite rods in my plating tank to reduce the concentration of copper in solution. to plate out copper onto a copper sheet.Graphite electrodes became etched and surface became granular.My problem was excess copper in solution.I run my plating tank at half an ounce of copper per 80 minutes. from memory thats about 6Amp per 100 square centimeter. I also use leveler and brightener to achieve a smooth high brightness finish on plated surfaces.Copper concentration is critical in the mix of parameters. Too much copper in solution and results are unsatisfactory. Copper electrode in my tank consists of copper spheres ( treated in hydrochloric acid ) and loaded into titanium baskets.The baskets are removed from plating tank when not plating. If copper electrode is left in solution it will further dissolve and its concentration will rise and plating will turn to pudding.Solution is also sensitive to chloride concentration.When the solution is just so...the copper is mirror bright, soft and ductile.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 07, 2018, 07:28:32 pm
content: You need a bit of sulfuric acid in there too. And, uh, I forget if you want a little chloride, or absolutely no chloride.The real trick is in the leveling agent. Absolute magic, that.The easiest to come by is thiourea, a component of Tarn-X (or just buy crystals of the stuff off eBay). Just a splash will do 'ya.I've done exactly this before:http://www.seventransistorlabs.com/tmoranwms/Chem_Chlorate5.jpgQuoteHuh, I forget if I ever peeled it off. I think the one had very good adhesion indeed, while the other that corroded (from porosity wicking anode gasses up to the plating) mainly failed because of corrosion. I think another had poor adhesion in areas, perhaps from poor surface prep, but that was discovered early.Tim

author: rhb
author_rank: Super Contributor
timestamp: June 07, 2018, 07:50:03 pm
content: You might want to get a copy of this:https://www.amazon.com/Electroplating-Electroforming-Artists-Craftsmen-Newman/dp/0517530597/I've attached the basic copper plating and forming information.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 07, 2018, 09:15:52 pm
content: Also, long-throw plating can be done with alternating polarity, where the positive and negative currents are whatever (equal, give or take?), the frequency is whatever (on the order of seconds, I think), and the duty cycle is over 50% (to net deposit material). AFAIK, this is used in PCB manufacture, along with leveling agents, to achieve plating in deep, narrow vias. Lower current density probably helps a lot, too (less voltage drop through the solution in narrow spaces).Hmm, long throw would be very important to the initial bond, on anything that's inert (graphite, other noble metals) or not perfectly polished (i.e., real rough surfaces, porous materials). If it's not getting into microscopic crevices, it's not going to be very strong.Tim

author: IconicPCB
author_rank: Super Contributor
timestamp: June 07, 2018, 10:53:58 pm
content: alternating plating and removal technique also known as pulsed plating is used to overcome the effects of field gradients in the plating medium, at sharp transitions on the plated surface.If not managed properly for example holes will end up with excess buildup around flat surface to hole transition area.This effect is sometimes referred to dog bone effect.Chloride is essential to promote dissolution of copper electrode so that healthy and stable plating can take place. Literally a grain of kitchen salt would be sufficient in small volume of copper sulphate solution. ( chloride should be between 30 and 60ppm more than 80ppm cuprous chloride electrode becomes polarised less than 30ppm will result in step plating in high current areas.)Too much chloride and copper goes into copper chloride an insoluble salt which prevents the copper electrode from dissolving . In that case only copper from copper sulphate is available for plating resulting in eventual copper starvation .Under no circumstance allow any iron into the plating bath Iron will displace coper and stuff up the process.

author: DTJ
author_rank: Super Contributor
timestamp: June 08, 2018, 03:01:16 am
content: Thanks to all for the responses - there's too much to address individually.Some great links to read up on and some good advice. THANKS!!!Looks like I may need to look at getting some sulphuric and try that adding some to the mix as well.I used to have some Potassium DiChromate in my 70's chemistry kit as a kid - looking at it's MSDS I'm surprised I'm still alive. I'll probably avoid it.I'll go and chase some leveling thiourea as well.Thanks again all - invaluable advice.

author: IconicPCB
author_rank: Super Contributor
timestamp: June 08, 2018, 04:44:19 am
content: Where are you located

author: DTJ
author_rank: Super Contributor
timestamp: June 08, 2018, 01:54:09 pm
content: Quote from: IconicPCB on June 08, 2018, 04:44:19 amPerth

author: Buriedcode
author_rank: Super Contributor
timestamp: June 08, 2018, 07:51:29 pm
content: Copper plating is difficult, although probably the least difficult of all metals - its still hard to get a practical plate (adherence, ductile, even etc..). It is also an industry full of "secret formulas" and a lot of bull.For the most part, the battle is cleaning the part to be plated, etching it for half decent adherence, and keeping contaminants out of the solution (both part and anode in bags).I have had some success using copper sulphate, sulphuric acid (standard acid bath) with PEG 4000 (try miralax, its close) as a cheap additive for levelling/brightness. It wasn't what I would call a mirror finish but it buffed up reasonably well.Unless you're doing this on an industrial scale, there is nothing wrong with slowing things down. Lower concentration of acid and copper, low current density = slower plating, but often with more even and denser deposits. And of course, electroplating requires a constant current source, or at least a variable voltage source with an ammeter.

author: IconicPCB
author_rank: Super Contributor
timestamp: June 08, 2018, 08:30:05 pm
content: If you want to..send me a piece of carbon rod and i shall attempt to plate it up

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 08, 2018, 08:43:37 pm
content: Sorry, had to...Tim

author: sdouble
author_rank: Frequent Contributor
timestamp: June 08, 2018, 08:47:16 pm
content: Does someone have some experience in plating nickel onto stainless steel (SS304) ?

author: jbb
author_rank: Super Contributor
timestamp: June 08, 2018, 10:03:41 pm
content: Quote from: DTJ on June 08, 2018, 01:54:09 pmI hate to be boring, but maybe you could just pay someone to do it? There must be electroplate shops somewhere around Perth.The big benefit of going to a shop is that you don't have to handle or properly dispose of the nasty stuff; in many countries spent electroplating solutions are considered hazardous waste and you can't just pour them down the drain.

author: DTJ
author_rank: Super Contributor
timestamp: June 09, 2018, 11:34:24 am
content: Quote from: IconicPCB on June 08, 2018, 08:30:05 pmThanks for the very kind offer. I'm just playing around with it myself so I don't really want to waste your time. A generous offer anyway.Quote from: jbb on June 08, 2018, 10:03:41 pmAll we are chasing is a fast reliable way to make an electrical connection to the rods. We've tried a few silver loaded epoxies and they are quite hard and messy to work with so I thought i'd explore the electroplating option. I think you are correct that it is too messy and potentially inconsistent to be applied to low volume work.Thanks gents.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 09, 2018, 08:46:20 pm
content: If you're working with small rods of known size, try gouging rods -- at the welding store.Tim

author: DTJ
author_rank: Super Contributor
timestamp: June 10, 2018, 12:39:17 pm
content: Quote from: T3sl4co1l on June 09, 2018, 08:46:20 pmYeah I spotted them, unfortunately they are too big - around 1/4 --> 3/8"We want 1/8"

author: IconicPCB
author_rank: Super Contributor
timestamp: June 10, 2018, 02:02:32 pm
content: Get some A ( may be B or C ) size batteries and scavenge the carbon electrode.Alternatively contact someone likewww.cortela.com.au/for precisely manufactured carbon component.DISCLAIMER..no commercial interest in Cortella.

author: DTJ
author_rank: Super Contributor
timestamp: June 11, 2018, 06:30:36 am
content: Quote from: IconicPCB on June 10, 2018, 02:02:32 pmThanks - we've got a source of plain rods, they're chemically pure 99%+ something or other. I think the intended use was for SEM sample coating. I think they were via Amazon. Poco Carbon is also a good source.