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topic 53012

Electrolytic Etching of Aluminum Plates


A discussion started in 2009 but continuing through 2019

September 2, 2009

Q. I need to etch large numbers of aluminum plates with a depth of at least 1 mm, so I want to do it with an electrical method as there is no time for chemical etching.

Ahmed Samy
handcraft shop - Egypt


September 28, 2009

A. Dear Ahmed

Electro etching is the best for aluminium
1-fast
2-low cost
3-accurate

My advise to you is:
-make the design in silkscreen
-print it on aluminium after proper cleaning
-use epoxy ink in printing
-dry it; in EGYPT maybe it take one hour
-then go directly to etching bath

which contains 250 gm/l of Fe2Cl3 [ferric chloride] acidified with 15 ml hydrochloric acid [HCl]
[-] electrode will be lead
[+] electrode will be your aluminium
Go to work, and happy good production.

Raafat Albendary
plastics electroplating - Riyadh, Saudi Arabia


September 28, 2009

A. In my opinion one millimeter is too much. More so if you don't have experience with either etching or electro etching. There will be a lot of under etch (tolerances and boundary lines lost). Most surely the paint will not hold either. Also, the etched surface will be too rough, and I mean it. Unless you want surfaces that look like coarse sandpaper, think it over. It is difficult to make a suggestion without knowing your parts but, perhaps you should consider CNC machining. Aluminum is one of the easiest materials to machine. Fast, clean, environmentally friendly, precise and beautiful surface finishes.

Guillermo Marrufo
Monterrey, NL, Mexico



June 23, 2015

Q. What is the composition of the electrolyte? What happens during electrochemical etching of an aluminum? What is the composition of the etched area? Is it porous? Will it take dye in the following class 2 anodize?
Thanks.

david ho
- milford, Connecticut USA


"Surface Treatment & Finishing of Aluminium and Its Alloys"
by Wernick, Pinner & Sheasby
from Abe Books
or
info on Amazon

June 2015

A. Hi David. Raafat has described the composition of the etching solution. It is the anodized layer itself, with its billions of microscopic drill holes, not the etched surface, which absorbs dye.

A look through Wernick, Pinner, and Sheasby shows electrochemical etching to be a really broad subject spanning several chapters and many subchapters, involving everything from electrograining for printing, to electroetching of capacitor foil. But if you can please introduce the details of your own situation to the discussion I think the readers will have specific things to say. Thanks.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


November 9, 2015

A. I have been etching plates for printing using electrolysis. The electrolyte is usually the salt of the metal to be etched, i.e., copper sulphate for copper, zinc sulphate for zinc and either ferrous sulphate or ammonium chloride for mild steel. The advantage that electro-etching has over traditional acid etching is that it: does not produce harmful gasses, the etched line is clean does not undercut the ground that is used to protect the un-etched parts of the plate, and the electrolyte is self sustaining.

The "same salt electrolyte" idea does not work with aluminium. Although aluminium can be etched in copper sulphate or a saline sulphate mix without electrolysis, the resulting etch is crude and erratic.

I have used sodium chloride as an electrolyte and get a good etch from it but have been told there is a danger that using sodium chloride might produce chlorine gas. I have also been told that if the anode is aluminium, not inert like carbon, the preferred action would be to etch the metal and not produce chlorine gas. As the aim is to etch the aluminium it is the anode and I use copper as a cathode. The other disadvantage to using sodium chloride is that it is not self sustaining.

Don Braisby
Artist - U.K.



December 21, 2017

Q. I want to etch an aluminium plate of size 450 * 450 * 0.5 mm. What is the procedure for etching such a big plate?

aniket tambavekar
- mumbai. india


December 2017

A. Hi Aniket. I think Raafat's and Don's replies are applicable because I don't think a plate of under half a meter square is "big", although everything is relative :-)
Is this plate for printing, or what kind of etching are you looking for and why? What exactly do you mean by "what is the procedure" that you feel was not answered? Thanks.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



February 27, 2019

Q. How important is electrolyte temperature in the process of etching aluminum? Also, are there some general guidelines on current density based on exposed etch area in the solution?

Background: I make reproduction machinery tags for restorers around the world. Brass is a joy to etch, but aluminum is the devil due to its reactivity and exothermic nature, at least in the chemical etchants I've tried so far (ferric chloride, copper sulfate/sodium chloride, HCL/hydrogen peroxide).

I've made a few attempts at electrical etching in saltwater--the electro-etching seems to start out well enough using a Lambda DC power supply set to between 2-6VDC and current-limited to 5A; however, within a few minutes the electrolyte becomes cloudy and progress toward any kind of depth crawls to a stop).

To try and understand what might be missing, I just purchased the 1964 (single volume) edition of Wernick & Pinner's book on surface treatments of aluminum. It's definitely not in my usual "swim lane" as I'm a mechanical engineer rather than a chemist, so I'm hoping it's not so far over my head that I won't be able to gain some usable insights.

Kind regards,

Tom

Thomas Utley
Von Industrial, LLC - Tucson, Arizona, USA



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