Electrolytic Etching of Aluminum

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 takes one hour
-then go directly to the etching bath which contains:

250 gm/l of Fe2Cl3 (ferric chloride ⇦ this on eBay or Amazon [affil links] ) acidified with 15 ml hydrochloric acid (HCl)
[-] electrode will be lead
[+] electrode will be your aluminium
Go to work, and happy good production.

A. In my opinion one millimeter is too much. More so if you don't have experience with 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.

"The Surface
Treatment &
Finishing of
Aluminium and
Its Alloys"
by Wernick, Pinner
& Sheasby

(note: this book is two volumes)

on eBay or

AbeBooks

or Amazon

(affil links)

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 very 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 situation to the discussion I think the readers will have more specific things to say. Thanks.

Regards,

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.

A. Hi Aniket. I think Raafat's and Don's replies are applicable because, although everything is relative, I don't think a plate of under half a meter square is "big", :-)
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 has not been answered yet? Thanks!

Regards,