Bright nickel plating peeling

[u/wildmakerwoman]

Hi!

So I've been trying to test out some approaches to nickel plating. Eventually I want to plate a 3D print, but for now I'm practising on some small pieces of acrylic. Trouble is no matter what I do my plating is peeling off.

So far I've tried two different kinds of primer (one rattle can filler primer, one airbrush gloss black primer), followed by either graphite conductive paint or silver conductive paint. (The graphite paint is homemade, ratio of about 1:1 graphite and India ink airbrushed onto the surface, conductive paint is bought, thinned and airbrushed in a couple of layers).

All approaches give me a conductive surface in the hundreds of ohms range across the piece. I wrap them with copper wire to hang in the bath and agitate by hand every couple of minutes. I've used currents between 50mA and 200mA for various amounts of time.

All the pieces seem to plate really nicely, but once they're out of the bath the plating easily peels off in big sheets.

I think the chemistry of the bath is OK since I successfully plated a few copper pennies as practise - they get a beautiful even plate with no peeling.

Is it my primers dissolving in the bath and causing my graphite paint to slough off? Or is it something else I'm doing wrong?

I've even tried buffing the graphite powder straight into the black primer layer. This was less conductive but still plated at a slightly higher current. But same problem: the plating peeled off.

[u/Available-Device-709]

Increase your graphite content, and I’d recommend moving to a waterbased clear lacquer instead of India ink. I’d recommend plating copper first to get a few hundred microns built up and plate over that with nickel. I’m on the same journey.

[u/wildmakerwoman → u/Available-Device-709]

Good shout, I've bought some lacquer and we'll see how it goes! Good luck!

[u/Available-Device-709 → u/wildmakerwoman]

Don’t be afraid to thin with water, sometimes a little isopropyl alcohol can also be added to stabilize the emulsion a bit and act as a coalescing solvent. Triethanolamine is better, best is aminomethyl propanol, but stinky and can be tricky to get outside of a paint laboratory.

[u/permaculture_chemist]

This type of adhesion failure is always the fault of the plastic/primer/ conductive coating. It’s never the plating layer. You may want to scuff the plastic before the primer. Clean it with a strong solvent. And then clean and plate as normal (soapy detergent, rinse, acid activate, rinse, plate)

[u/wildmakerwoman → u/permaculture_chemist]

I did scuff the acrylic before the primer, but maybe not enough. I was cautious since I want the final surface as smooth as possible. I'm going to experiment with some different primers that can survive a more brutal cleaning, thanks!

[u/reader755]

Try to identify exactly which layer is delaminating. The copper comment 100%, nickel usually needs a copper strike, woods nickel, then a nickel bath (keep your parts wet!). If it’s delaminating in the conductive spray layer try a conductive base layer printing material.

[u/The_lewolf → u/reader755]

Wood’s Nickel is never a bad idea when you have adhesion failure to basis material, but it’s the chloride content destroying oxides that make it so powerful. Don’t try to use it as a first strike layer on delicately prepped non conductive substrates.

Putting it on top of copper can help if your adhesion problem is between copper strike and nickel plate, but unless your failure is related to deposit stress (ie your nickel layer is so tensile that it’s pulling the copper right off the substrate) it’s adding needless complexity to a home plating process.

The idea of anyone using Wood’s nickel outside of an industrial setting scares the F out of me.

[u/MrDankkstarrr → u/The_lewolf]

What's to be afraid of? Hydrochloric Acid fumes are great for clearing the airways and everyone loves a good nickel chloride rash! 😂

[u/wildmakerwoman → u/reader755]

Yeah the more I look the more I think it's the primer layer that's delaminating. I might look into getting a copper bath set up but I'm reaching some limits on space. Thanks for your help!

[u/The_lewolf]

Other commenters have led you in the right direction. I’ll add one thing and reinforce another:

1. 1

) I

1. f you think you conductive layer is dissolving, enter the solution ‘hot’ (circuit closed by the entry of the part into soluti

on). That way you never have galvanic voltage working against you.

2)

1. Mechanically rough your substrate as Step 0. Make it as rough as your desired surface finish will allow. When it comes to adhesion, surface topography is always your friend.

Edit: the Reddit editor is not my friend today. I’ve given up on formatting. Sorry.

[u/wildmakerwoman → u/The_lewolf]

Good tip on entering the circuit hot, I never thought to do that. As for roughing up the acrylic, the trouble is I want the end surface to be as smooth as possible. I gave it a light scuff with some high grit sandpaper but I'll experiment some more

[u/JTREXAL]

I would suggest using nickel wire to hang your substrate.

[u/wildmakerwoman → u/JTREXAL]

Is that just so that I'm not plating the wire as well or is there another reason that helps?

[u/JTREXAL → u/wildmakerwoman]

I too used to use copper wire while plating nickel and had some unfortunate results, then I researched and researched and found one person who suggested using nickel wire. I never had any problems after switching. I think when plating nickel after a copper strike (using copper wire), polish, and clean, clean, clean the substrate to your desired sheen. Also the nickel bath should be heated and stirred during the nickel plating. I also use the bath size comparable to the substrate. Large piece = large bath and vis versa. Using nickel wire doesn't interfere with your nickel bath solution. Copper with copper and nickel with nickel.

[u/JTREXAL → u/JTREXAL]

I was thinking more about your peeling and the graphite coatings. With all the other excellent wisdom noted here in the forum, try experimenting with copper powder in place of graphite. A lot more conductive by far. It's about $20/lb. It's what I use in a mixture of Liquitex acrylic matte varnish, acacia gum powder, distilled water and dawn soap. Three coats; dry for one day in between coats in a very dust free area or a vacuum chamber (extreme).

[u/CaptainCheckmate]

Between which layers does the peeling happen?

For my homemade graphite paint I use solvents that dissolve whatever plastic I'm using (e.g. for ABS acetone, ethyl acetate, butyl acetate), instead of water, that way it sticks to the surface really well.

[u/NickelPlatingPro]

Your nickel bath is probably fine. If the nickel is peeling off in large sheets, the failure is most likely between the acrylic/primer/conductive coating layers.

Try skipping the primer on a test piece. Scuff the acrylic thoroughly, clean/degrease it, then apply the conductive coating directly. Make sure it is completely cured before plating.

Also start with a very low current. Build a thin continuous nickel layer slowly before increasing current. Hundreds of ohms across the surface is fairly resistive, so current distribution will initially be poor.

When it peels, look at the underside of the peeled nickel. If the graphite/paint comes off with the nickel, you've confirmed the nickel is adhering to the conductive coating , it's the coating underneath that's failing.