Decorative electrolytic metal etching, plating and marking. - Page 1
Forum section: electronics / projects

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 24, 2016, 06:50:00 pm
content: Edit: I know, this is not the right forum to ask this, but it feels like here i have the highest chance to find someoneHello!A few weeks i went down the rabbit hole... combining electronics with chemicals seemed like a fun thing to try.There are many wrong or incomplete informations in the web about this, i learned that the hard way.So many people saying "This will not work!" but it does work wonderfully on my workbench.And the opposite just as often, "Try this, this will work!" and it failed horribly.I am at the stage were i can get semi reliable results.I am focusing on decorative stainless steel etching at the moment, once i have that covered solid i want to switch over to aluminum front plate marking and etching.Here are a few pictures of my first attempt:http://imgur.com/a/ZJ6NkSince then i have upgradet everything heavily but my new power supply/controller/stirr plate/heater is still in the process of beeing build and i have no pictures of that.So... my question, is annyone here with practical experience in this field that would be so kind to let me pick their brains a bit?Or if someone is interested i would do a proper write up of the things i dit and learned.Greetings,Peter

author: MickM
author_rank: Regular Contributor
timestamp: March 24, 2016, 09:20:05 pm
content: Hi;That is very impressive.You picked a difficult metal to play with.Hard to drill / cut etc.Have you tried toner transfer, rather than stencils?Hopefully aluminium will etch quickly before the toner perforates.For you chemical guys - is there an electrolyte that will etch and colour aluminium?Mick M

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 24, 2016, 09:49:06 pm
content: Quote from: MickM on March 24, 2016, 09:20:05 pmI hate the stuff with a passion, yes.That is why i started with the etching, it was the only method i could think of that works with stainless without beeing a royal pain in the neck.Edit: One of the things i learned about it, many people said:"You can not electroplate stainless with copper, it simply does not work."I have succesfully and permanently plated stainless 3 times now with extremely good adhesion and twice with not that good results.There will have to be a lot of tinkering ahead of meQuoteI tried toner transfer many years ago, for PCB etching, and never could get it to work reliably. I do not want to try it again.I have seen people use toner transfer to electro etch aluminum, tin and copper.The results look nice but not up to my standards when it comes to surface/edge finish.QuoteI am fairly certain that it works the same way for steel then aluminum and there you have to differentiate.You etch (depth) with DC and mark (color) with AC current, the electrolyte removes the metal of the workpiece and then deposits it back onto the surface.You either get a deep etching (DC) or a marked etching (AC), if you want to have a marked and deep etching you need to first etch with DC and then mark it with AC.For that i have plans to use a motor driver h bridge (maybe it will not work) instead of an transformer to "automate" the whole process with precise frequency, current and voltage control.I got a hunk of graphite to use as an electrode for the marking and etching of bigger pieces that do not fit in the tank.For stainless i can answer your question i think, i only got the recipie for now:Citric Acid, sodium nitrate, Sodium metabisulfite and Acetone.At least that will be my starting point.Edit: To be honest... my first try marking will be just with citrus juice and acetoneGreetings,Peter

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2016, 07:18:25 am
content: For aluminium try some KOH or Naoh, as it will strip the oxide layer off very effectively. It will etch, but will grow a thick oxide as well, and will undercut quite a lot. For dying grow a thick oxide layer and then some Azide dyes, as the porous oxide will trap the dye quite effectively.

author: IconicPCB
author_rank: Super Contributor
timestamp: March 25, 2016, 01:14:02 pm
content: Have seen stainless steel electropolishing..dangerous stuff..cyanide/lead combination...great results..but real dangerous chemistry...

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 25, 2016, 02:49:50 pm
content: Quote from: IconicPCB on March 25, 2016, 01:14:02 pmI have seen that as well but with way less dangerous chemicals, you get old patents for the process they do not list really dangerous chemicals.Here is the recepie i have on my list to try, for electro polishing:1 part by volume of 80% phosphoric acid1 part by volume of propylene glycol1 part water1/4 part isopropanol0,1 grams dish soapThe only "dangerous" thing is the phosporic acid, but remember, this stuff is used as a food additive.

author: sca
author_rank: Regular Contributor
timestamp: March 25, 2016, 02:51:09 pm
content: I did a lot of work on Electrochemical Machining many years back.Saltwater and stainless will indeed 'machine' very well, however be aware that the chrome from the stainless can end up as hexavalent chrome in your used electrolyte. It is not particularly nice stuff, and disposing of it is often, at least in theory, well regulated.sca

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 25, 2016, 04:10:00 pm
content: Quote from: sca on March 25, 2016, 02:51:09 pmThanks! I am aware of that and allready looked up how to dispose of the used electrolyte, i should be able to get rid of if through our local hazardous waste disposal service.I looked up how to convert the chrome oxide using ammonia and percipitate it out, but that was a bit over my head.Greetings,Peter

author: IconicPCB
author_rank: Super Contributor
timestamp: March 25, 2016, 09:21:41 pm
content: The process I aluded to above relied on a lead ( Pb ) electrode. Bad Juju.

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 25, 2016, 10:44:49 pm
content: Quote from: IconicPCB on March 25, 2016, 09:21:41 pmI am exposed to lead and lead oxides waaaay above the average, so... that i will most definately not try.Even though i have some left over lead bars around, but they keep my radioactive stuff "safe" for the moment