Electrolytic Etching, For What A Dremel Can't Do 242
Dustin writes "A lot of people modify computer cases, often requiring them to cut intricate custom designs in
sheet metal. For most, there is the Dremel tool. But
sometimes, that just isn't good enough. Possibly due to an insanely complex design, or
unsteady hands, a Dremel just might not cut it (pun honestly wasn't intended). JimBob, a member at OverhauledPC.com, has a much better way. Using
readily available salt water and electricity, his technique is much easier than trying
to cut patterns with a rotary tool."
Coral Cache, just in case... (Score:4, Informative)
Here's the Cache Link [nyud.net] if it's needed.
Mirrordot Link (Score:1, Informative)
mirror (Score:5, Informative)
To summarize... (Score:5, Informative)
You take two plates of metal and hold them parallel (not with your hands, they're going to be electrified!) underwater. Electrify the plates and the positive ions in the water will collect at the negative terminal and the negative ions will collect at the positive terminal. By adding some salt to the water however, you can encourage a chemical reaction to happen at a given electrode. By covering the metal with paint or duct tape, you insulate it from this effect. So what they're doing is, essentially, painting around the hole they want to cut, leaving the hole itself barren, then submerging it in saltwater and electrifying it, causing the exposed metal to oxidize and be eaten away.
It's roughly the opposite of electroplating, which is the procedure which this technique is likened to in the article. Instead of trying to accumulate more on a given electrode you're trying to reduce the amount of matter present there.
methane gas???? (Score:2, Informative)
Can also be done in a much simpler... (Score:5, Informative)
FeCl3 is cheap, relatively safe (don't eat it kids!), and easy to handle. It stains like a bitch though, and will attack most metals so be careful with spills.
I used to do that with nitric acid (Score:4, Informative)
Re:Salt + Electricity... (Score:2, Informative)
Unfortunately, I was unable to load the article - so I can't comment on the procedure involved. But if you haven't studied electrochemistry to at least a small extent to know whats going on (and I know people with B.S. in chemistry I wouldn't trust with understanding reactions in this catagory), its best you DO NOT try this. The procedure listed may be completely harmless, I can't say without having access to reading the procedure. But if you are someone (like most slashdotters) who doesn't hesitate at "improvising", stick to the dremel.
Re:To summarize... (Score:5, Informative)
By adding some salt to the water however, you can encourage a chemical reaction to happen at a given electrode.
No, the salt is to reduce the electrical resistance of the water and create a greater current flow. Pure water actually has a high amount of electrical resistance. Oxygen will collect at the positive electrode, and hydrogen will collect at the negative (the article author is a bit confused and thinks this is methane).
You're correct about the rest of your summary though.
Re:Can also be done in a much simpler... (Score:2, Informative)
Something as simple as a magic marker can be used, but it will probably look like ass. A better idea is to use a photo-resist kit. With this you spray the metal surface with a chemical that will protect it from the FeCl_3. The kicker is that light will eat away this protection. So you print your design onto an overhead transparency or something, place that atop the metal, and affix it to a window for a while.
Using these kits is a great way to make high quality designs, and it easy to transfer the design to the metal surface. The drawback is a limit in size and perhaps cost
Computer chip manufacturors use essentially the same technique, except their designs are so small that the wavelength of visible light is too wide! So they moved towards UV and now are starting to have a lot of problems trying to shrink farther.
I went to radio shack's site to look up some info on PCB etching kits and, seriously, far too many of the search hits were for HP computers and photo-printers. So sad...
Easy design masking (Score:3, Informative)
Easily done. Head to Techniks [techniks.com] or some other similar place and get some Press 'n Peel PCB transfer film.
Draw what you want to etch as a negative and then iron it onto your metal. Dip the whole thing in the acid bath and wait a bit. Steel wool to clean off the resist and that should do it.
If you're really cheap, toner is a decent resist. [fullnet.com] No different than making a homebrew PCB.
Re:Can also be done in a much simpler... (Score:3, Informative)
1) Press-n-peel blue [southcom.com.au], which is a sheet of material that will stick to a surface only where it's printed. It's hard for me to find it where i live, so what i use is...
2) Laser printer and satin ("photo") paper. Laser printer toner is 100% waterproof and melts when heated; you print you design, mirrored, onto a satin paper sheet, then iron it over the metal (previously cleaned and degreased with alcohol), and carefully peel it, soaking it wet if needed. If done right the toner sticks to the metal, making a perfect etch mask.
I do this all the time and it works great; just google for more info on the procedure.
Both work great for PCBs. If you need to etch a piece of metal, you do the same and paint the sides of your metal block (a waterproof marker works just fine). You clean it well with water to remove the etchant and isopropyl alcohol to remove toner/ink, and voila!
A link dug from the hurlage (Score:2, Informative)
http://gravert.club.fr/galvetch/contfram.htm
Re:What about what a Dremel CAN do? (Score:1, Informative)
I doubt we would sold a tenth as many without those little plastic toys suckering people in. Thanks, Dremel!
Re:Can also be done in a much simpler... (Score:3, Informative)
I have forgotten a lot of chemistry over the years. I thought Ferric Chloride works as an etchant for copper because the chlorine prefers copper to iron so it is happy to trade an iron atom for copper. But why would it trade an iron atom for another iron atom? Now in a solution, there will be free chlorine and iron ions floating about so the chlorine may etch the steel but I would not expect it to do as well as a compound that combined chlorine with something less desirable than iron. Maybe FeCL3 would rather combine with another Fe to produce two molecules of FeCL2. That would make sense. Some people do use ferric chloride on steel and stainless steel but reportedly it quickly builds up an oxide layer on steel [dfoggknives.com] that must be sanded off before it will continue etching. In stainless steel, the ferric chloride attacks the chromium (chromium chloride is very soluable in water) so it neutralizes the "stainless" in "stainless steel" making it more vulnerable.
I also wonder why you suggest FeCL3 is safer. Is this because there is no need for an electric current (and the free oxygen and hydrogen it produces?) which produce an explosive gas mixture and may also combine with components of steel to make other compounds.
Re:To summarize... (Score:2, Informative)
Chlorine gas is poisonous. Fortunately it's heavier than air so it shouldn't fill the room or anything. Sodium hydroxide is caustic.
MJC
Re:Acid? (Score:3, Informative)
Resists: You need something that is resistant to the acid, but can be applied neatly, and removed neatly afterwords. It needs to adhere well to the metal surface, yet be resistant to the acid and to water, and any by-product produced. Also, it needs to be resistant to exfoliation - as you start to etch, it's no good if your resist falls off around the cut. Oh, and it needs to be cheap and easily available.
Rates: Acid is slow. Or, rather, acid's that you would want to use for this purpose are slow. Anything that can eat through steel or aluminum at a decent rate is not something you want to handle. (Consider: What do you store it in, and what do you do the reaction in? Both are doable - but not strightforward). So you're left with acids that don't eat the metal very fast.
Edges: With an electrical current, you can ensure that the direction of cutting is more or less perpindicular to the surface of the metal (that's why it's two large plates, for example). With an acid, that's not the case. They will tend to etch out round indentations under the edges of the resist - giving you razor sharp edges to your cut out. Which would need filed down afterwords, and means there is a minium thickess of cut, proprtional to the thickness of the sheet.
My back of envelope sums suggest that the miniumum width of cut by acid etch is roughly equal to the thickness of the material, assuming an infitessimally small start. For 1.2 mm sheet metal, that's a 1.2 mm width - easily doable with a Dremel.
It would also take around 3-4 months, I think.
Acids are good at etching a surface layer. I would use an acid if I wanted a matt surface - for example, to etch details onto sheet metal. A combination of cut outs and etching would work very well in giving a unique appearence to a panel.
Re:"much easier", where's the fun in that? (Score:2, Informative)
Re:Wait a minute. (Score:3, Informative)
And chlorine isn't good for the metal either. If you are interested in preserving the mechanical properties (especially the surface properties), using chlorine in an electrolytic metal removal process is a bad idea (in general, any electrolytical metal removal process will contaminate the remaining surface). Many bad types of corrosion are started with just a little bit of chlorine. Do a google search for chloride stress corrosion cracking [google.com] for one of the very worst types of corrosion known.
Anyone interested in using electrolytic metal removal for any project that is under high temperature and stress (a case mod *probably* won't qualify) should definately not use the NaCl procedure. In fact, if you ever want to do a project under high temperature and stress you need to carefully monitor the exposure of chlorine, oxygen, hydrogen, and sulfur ions (to name a few) as well as things like the pH to ensure that your piping doesn't fail.
Re:To summarize... (Score:3, Informative)
Salt = Bad (Score:3, Informative)
Use baking soda or sodium hydroxide instead. Either electrolyte will give off substantially less-dangerous byproducts.
p
Not H2+O2- H2+BLEACH! (Score:2, Informative)
The 40% solution mentioned in the article probably limits the strength.
Keep it off of your 501's or we will know you can't use a Dremel tool.
From: Electrochlor.com [electrichlor.com]
1.2 Reactions
The principle reactions occurring in the electrolytic cell that produces sodium hypochlorite are quite simple, as shown in the following:
Oxidation of the chloride ion occurs at the anode:
2Cl- -> 2Cl2 + 2e-
Followed by a rapid hydrolysis of the chlorine:
Cl2 + H2O -> HOCl + HCl
Reduction of the sodium ion occurs at the cathode:
Na+ + e- -> Na
Followed by a rapid reaction of the sodium with water:
Na+ + H2O -> 1/2H2 + NaOH
The acids (HCl and HOCL) produced at the anode react with the base (NaOH) produced at the cathode:
HCl + NaOH -> NaCl + H2O and,
HOCl + NaOH -> NaOCl + H2O
The net reaction of electrolysis is:
NaCl + H2Oe- -> NaOCl + H2
The amount of hypochlorite produced is related directly to the amount of direct electrical current passed through the cell.
Easier to read on web site. I had to hack in '->'s.