Etching Enclosures - or things I didn't know about FeCl

[frequencycentral]

Ok, so 6 months ago I bought 500ml of 60% FeCl off Ebay and learned to etch, with the help of Slade's excellent tutorial:

http://dl.dropbox.com/u/3565959/%5BTutorial%5D%20Making%20a%20Multicolor%20Etching.pdf

......and tips from the man himself. I used the FeCl as is - undiluted, and found that I needed the enclosure immersed for 30 minutes to get a good etch. Didn't seem to be a 'big reaction' taking place, a little bubbling, no heat to speak of. It's gone well so far, done some really nice etches:



So, I exhausted my FeCl, I decided to order 5L of 40% FeCL from Rapid in the UK:

http://www.rapidonline.com/Tools-Fasteners-Production-Equipment/PCB-Equipment/Etching/Ferric-chloride-solution/61309/kw/ferric+chloride

Now, this stuff is 40% as opposed to the 60% I was using, so in my innocence I figured it's a weaker solution so it'll need more time. WRONG!! I gave it 30 minutes, and got a really shallow etch, but worst of all, the FeCl had started to eat the toner! Feck! The enclosure was badly pitted in the areas 'protected' by toner. WTF?

That was yesterday. Spoke to Etch Master Slade. He said to try diluting the FeCl, so I did. Two parts FeCl to one part H₂0 (ie water). Stuck my enclosure in the 'weakened, diluted' (yeah right) etchant. WTF!! Heat, bubbles! HEAT!! Seriously hot heat. Seriously BIG bubbling reaction. I'm a fkg alchemist already.  So I think 'no way is this enclosure staying immersed for 30 minutes, I'll give it 20'. So 20 minutes late I pull the box, rinse it and clean it off - seriously deeeeeeeeep etch, and still a little pitting of the areas 'protected' bt the toner. But usable once prepped with wet and dry.

So what's going on here? I'm not a chemist, I'm a keyboard player (point and laugh) / wanna be guitarist / pedal whore. In my world diluting something means it's not as strong. But my FeCl tells me that diluted it's more reactive. I don't understand. FeCl is obviously different to orange squash in more ways than one.

Anyway, I'm getting there, it's just a case of setting myself new parameters for my new etchant. Next time I'll try 10 minutes, hopefully that will give me a decently deep etch but no pitting of the toner covered areas. Live and learn. I can get my process right by trial and error. But I want to understand.

[defaced]

Two possibilities I can think of:

1) The first FeCl you got was junk

2) You're getting more oxidizing out of the "weaker" solution because the pH is being messed with. 

When etching, work the other way.  Don't let it sit for 10 minutes when you can just check it every two minutes five times and get the same result.  In alot of my metal etching experience, metallography, every batch of etchant has to be watched to "learn" exactly how it's going to react because the procedure that works with one batch of etchant may not work with a new etchant.  To do this we polish a sample, pep the etchant, and then watch the same like a hawk to make sure it doesn't burn (over etch) by checking it's etching progress periodically.  If it burns, you get to stand at a polishing wheel for another 10 minutes re-prepping the sample.  Not fun. 

[deadastronaut]

hmmmm..thats definately weird!...

ive never used the liquid (bottle) gear.. i have only ever used the bags of orange balls ferric chloride..
and i definately have to up the strength to get a deeper etch...with a little warm water...then it will fizz...
it takes ages if its not strong enough with that stuff!..

if it is strong it takes around 20-30 minutes to get a real good etch...

but yeah maybe the first lot was dead!..i'm no chemist either!...

[defaced]

Just a thought, are you using the same batch of boxes?  Specifics to the alloy composition can effect how it reacts. 

[phector2004]

I could be wrong, but I think in the case of aluminum it's the HCl byproduct of FeCl3 in water doing most of the etching... And with more water, you're getting more HCl.

Too lazy to calculate how many moles of each would be in an x% solution but I think the chemistry is 1FeCl3 + 3 H2O <--> 1 Fe(OH)3 + 3 HCl... and then there's all that acid-base chem with the Ka's and stuff that I can't stand. I'll let you figure it out on your own 

[ACS]

Ah, now that's interesting indeed.  I wonder if it's the same HCl eating the toner, or if that's the FeCl itself?  If, find the optimal concentration for the FeCl in water to get the most etch / least toner eating...

Very interested here, as those little microdots where the toner's been eaten are really bugging me...

[phector2004]

Actually, I think I'm completely wrong about the HCl...

Must have been a bad batch the first time 

[deadastronaut]

i always use nail varnish over the toner on any unetched areas just to be sure...voil'a no pitting...

better to have a nice box, than a load of holes......

[jbgron]

I've found that different enclosures have different etching times.  I use 42% FeCI and it takes 20-30 mins for a good deep etch on a ProsKit 125B enclosure but only 15-20 mins on a 4-Site 125B.  Learned that the hard way of course

[R.G.]

N.B.
The actual material in die cast enclosures is not pure aluminum. It's usually some alloy, and may well have a significant and varying amount of zinc in it. Different manufacturers, different runs with different ingots from different sources...

You get the idea.

You also begin to understand why consistency is more valuable to a manuafacturer than a fraction of magically-good results.

[gtudoran]

Ok ... i will try to make a little light here (i didn't read the whole thread but i hope i don't repeat).

Regarding this i will give you an example: HCl and H2SO4 (high concentration) can be stored in metal containers - the acid is so corosive that corrodes immediate and the metal cover with a thick layer of oxide, wich don't react with acid.

So this fact is also true for FeCl 60% and 40% - for all guys who corrode using 60% or 40%, try to add some water in it and you will see that a much faster corrodation process is taking place.

I hope i was helping.

Best regards,
Gabriel Tudoran
Analog Sound

[Pigyboy]

A few variations I have adapted using Slades tutorial involve using standard thickness glossy paper instead of photopaper. After I make the heat transfer I soak the box with the paper on it in water for about 5 minutes then I carefully roll the paper away from only the areas I want to etch and leave the rest to protect against the acid. You can see a film of paper sometimes still covering the metal you want to etch after you have rolled away to bulk of the paper so I take a piece of the blue masking tape(regular white masking tape seems so have too strong of glue) and lightly tack it over the paper remains I want to remove and it usually leaves a nice crisp line where the lettering is. Then I tape it up and paint the edges with fingernail enamel.  I use all of my old FC acid that doesn't seem strong enough to make boards with anymore. I have a plastic tube I pour it in and then heat it up in a microwave for about a minute and then lightly dip and jiggle the box around in the acid. Every few minutes I pull it up and very easily with a soft toothbrush brush away the metal the acid has eaten away. Try not to rub too hard as you may remove the toner. Using the old acid I am getting etches like those pictured in about 5-7 minutes. I did use fresh acid once but the box got so hot so fast I could barely touch it.

I did both of these etches yesterday

So Rick, try using glossy paper instead of photo paper and be diligent about only removing the paper where you want the etch and leave as much as you can to protect the box with this done I think the strength of the acid will only affect the length of time needed to make the etch and not be able to get through to unwanted areas of the box.
Hope this helps a little.
Cheers,
Chris

[Perrow]

FeCl is obviously different to orange squash in more ways than one.

This was sooooo close to making it into my signature, it would've hadn't the fundraiser thread come up.

[JKowalski]

FeCl has always given me an outrageous reaction with aluminum. I only use my storage of used FeCl to etch aluminum from now on. It's a decent reaction pace.

I think the toner is being destroyed by the heat of the reaction, not the FeCl directly. To reduce the heat of my reaction and keep track of the etching process I usually dunk it for a few minutes, pull it out & rinse, dunk again, etc.

[Galego]

Another thing to take into account is the amount of aluminum your graphic leaves exposed. The more aluminum is in contact with the FeCl, more the solution will heat and the reaction will be much faster/violent.

[dcjim]

I'm about to try enclosure etching with sodium persulphate which is my preferred chemical for PCB making over ferric chloride. Will it work? It certainly did with a 5 mm copper plate. I left it in for about 2 hours and got 2-3 mmm deep grooves. But that was for something else. This is for pedal enclosures. The box is aluminium.

Suck and see I guess!

[frequencycentral]

Yeah, suck it and see indeed! Thanks for all the tips and advice gentlemen. Today I tried a test etch. Did a toner transfer onto the backplate of an old enclosure. Thought I'd try masking off areas and testing different ratios and timings. I think I got it right with 50/50 of my FeCl to water. Not a violent reaction, just a little heat, no crazy Jekyll and Hyde bubbling. I soaked and agitated for 20 minutes, rinsed it and cleaned it up. Looks good, may benefit from a few extra minutes, 25 in total maybe. Most importantly, no pitting of the toner masked areas. I'm happy, but gonna do a few more tests on my lab rat before I destroy another £10 enclosure.

[deadastronaut]

i think this guy got his mixture just right...

http://www.youtube.com/watch?v=UqkeemU7fyk

[bluesman1218]

i think this guy got his mixture just right...

http://www.youtube.com/watch?v=UqkeemU7fyk

Hey, wasn't that DougH's organ, from the Dumpster Dive thread, playing the background music?

[Govmnt_Lacky]

A few variations I have adapted using Slades tutorial involve using standard thickness glossy paper instead of photopaper. After I make the heat transfer I soak the box with the paper on it in water for about 5 minutes then I carefully roll the paper away from only the areas I want to etch and leave the rest to protect against the acid. You can see a film of paper sometimes still covering the metal you want to etch after you have rolled away to bulk of the paper so I take a piece of the blue masking tape(regular white masking tape seems so have too strong of glue) and lightly tack it over the paper remains I want to remove and it usually leaves a nice crisp line where the lettering is. Then I tape it up and paint the edges with fingernail enamel.  I use all of my old FC acid that doesn't seem strong enough to make boards with anymore. I have a plastic tube I pour it in and then heat it up in a microwave for about a minute and then lightly dip and jiggle the box around in the acid. Every few minutes I pull it up and very easily with a soft toothbrush brush away the metal the acid has eaten away. Try not to rub too hard as you may remove the toner. Using the old acid I am getting etches like those pictured in about 5-7 minutes. I did use fresh acid once but the box got so hot so fast I could barely touch it.

I did both of these etches yesterday

So Rick, try using glossy paper instead of photo paper and be diligent about only removing the paper where you want the etch and leave as much as you can to protect the box with this done I think the strength of the acid will only affect the length of time needed to make the etch and not be able to get through to unwanted areas of the box.
Hope this helps a little.
Cheers,
Chris

Chris,

These are BEAUTIFUL     

I still want to know your process for getting that spit-shine on the boxes