Make Ferric Chloride (for etching printed circuit boards)

video Make Ferric Chloride (for etching printed circuit boards)
We make ferric chloride, a well-known etchant for printed circuit boards.

Get 20g of iron. This can be in the form of nails or steel wool. It's best to use iron that's rusting, that indicates it doesn't have other metals like zinc or chromium that's normally used to prevent rust. To the iron add 100mL of water and 100mL of 12M hydrochloric acid. The iron will start reacting with the acid to produce hydrogen gas and ferrous chloride. If the reaction is proceeding too slowly for your liking you can heat up the mixture. A flask of cold water on top is useful to reduce evaporative losses.

Once the ferrous chloride solution is made it needs to be oxidized to ferric chloride. The fast way of doing this is to add 200mL of 3% hydrogen peroxide. Do this slowly with lots of stirring as the solution will heat up a lot. If it gets too hot to hold (about 60 celsius) stop and let it cool before adding the rest of the peroxide. If you don't want to use peroxide the slow and cheap way of oxidizing it is to bubble in air using an aquarium pump. It can take several days but it has the added advantage of keeping the solution concentrated.

After oxidation you'll have a solution of ferric chloride ready for use.
ClownW17 days ago

I have made a batch of Iron (III) using your protocal and it reduces to a chocolate brown and does not fall out of solution in crystal form..... I cant figure it out. I use rusty nails and the same ratio of di water to hcl... I reduce it slowly. More like evaporation. It just gets thick and then turns into a hard puck that looks like chocolate.

Any help would be great.

What is the advantage of ferric chloride over just hydrochloric acid (aka muriatic acid)?
Ferric chloride can leave really pretty stains on your clothes and counter ;)

I am not really sure you can call an advantage here. Stripping copper through chemical processes creates a resultant substance that you need to treat carefully, the spent copper-laden corrosive is fairly toxic and many states require you to take it to a approved haz-waste collection site. I think NR is doing the awesome thing of making everything from base materials, the holy grail of us 'structable nerds.

Back to advantages for a second though, I have read the cupric chloride etchant( I believe that is what you referencing) can be reinvigorated and thus it has a longer used life ounce for ounce. It still need to be treated with respect and caution.
To reinvigorate the solution you can simply add more Hydrogen Peroxide or you can use the air bubbler method, using an air stone at the end of the bubbler tubing helps reinvigorate the solution a bit quicker. If you insist on disposing the solution down the drain then at least precipitate the copper from the solution first by adding some iron to the solution, this will precipitate the copper in to it's solid form which can be disposed of separately.
dimeH stihl881 year ago
collect a bunch of machine shop turnings (swarf) and stuff into large, protein-supplement body-builders wide-mouthed plastic jug. Pour the toxic, spent-etchant into and onto the iron-turnings. Let sit overnight. Copper will precipitate out as grey, super-fine powder (copper hydroxide).

Pour top inch of reclaim-liquid into second iron-shavings jug as top inch of reclaim is foamy and toxic-looking. Under this foamyness is emerald green,
"de-coppered" iron (two) chloride. Pour this into empty jug. Stop decanting
this fraction when it begins to appear murky-grey. This, of course, is the copper
hydroxide becoming entrained.

Add 30Vol H202 to convert emerald-green Fe(2)Cl into our desirable (brown) Fe(3)Cl.

The reclaimed Fe3Cl is less-potent-an-etchant than the original store-bought Fe3Cl and tends to spontaneously convert back emerald-green Fe2Cl (not sure why?) but addition of additional beauty-supply store 30Vol H202 "re-energizes" things.

Household ammonia, cut 50/50 with tap water, "neutralizes" any spills and may
take fresh Fe3Cl stains out of carpets and clothing.

Weigh in with your thoughts on how to increase etchant-strength and "staying power" of reclaimed Fe3Cl.
The advantage I was talking of was that FeCl does a better job of etching.

That is it creates sharper edges and finer details. Was not making a moral judgment on value/environmental-friendliness/street-cred. It just works better at eating metal in a controlled manner.

CuCl is close to the results of FeCl on copper. But on some other metals it does not come close.
Ferric and also Cuperic Chloride do a much better job of etching detail than HCl + H2O2. Ferric also can be used on a range of different metals than copper.
oanderson2 years ago
Ha! It's interesting to see you here, after having subscribed to your youtube channel :) Good stuff
Orngrimm2 years ago
Maybe a stupid question...
It produces very unhealthy fumes if you evaporate it, right?
Is there a temperature-limit in evaporation i shouldnt cross (Decomposing stuff)?
Or is it even best to let it sit without raised temperature till it is evaporated?
Never realised Nurd Rage was on instructables too,have been a subscriber to him on youtube nearly 2 years now.
Happy to see him here :)