The finishing.com Hotline: Serious Education ... plus the most fun you can have in metal finishing. Ted Mooney, Webmaster
Q. I have been trying to etch 6061-T6 aluminum with sulphuric acid, straight and with water, and had no fuming no etching, no heat. Also tried nitric acid, full strength and diluted and no results.Any suggestions on how to etch numbers in smooth aluminum plate?Robert G [last name deleted for privacy by Editor]
welding - Cheshire, Connecticut
Q. I have tried my best to etch the aluminium sheet but failed. I also used nitric acid, sulphuric and hydrochloric acid. I shall be grateful to you for your kind advice and suggestions.
Thanks,Haiderali L [last name deleted for privacy by Editor]
- Karachi, Pakistan
Ed. note -- Robert, Haiderali: Can you please provide context so that we can understand what "etch" means to you? Aluminum can be etched as an aid to revealing its metallographic structure; aluminum surfaces can be etched to provide a matte anti-fingerprinting look; it can be etched in patterns for lithographic/printmaking applications; it can be etched and dissolved all the way through to make shaped components, etc. Different etchants and techniques will be preferred depending on the application.
A. Acid anodizes aluminum (forms aluminum oxide adsorbed on the surface). It is often faster to etch aluminum using caustic soda (NaOH). At least based on my experience.Aubert E [last name deleted for privacy by Editor]
- Chandler, Arizona
A. 10% Nitric acid, 1% Hydrofluoric acid, and 89% Distilled water should do it :)Angel V [last name deleted for privacy by Editor]
- Las Cruces, New Mexico
Ed. note: Please see the "thumbs down" entries below about the use of hydrofluoric acid.
A. I'm using ferric chloride (FeCl3) to etch aluminum right now with pretty good results. I got it from a PCB etching kit from Radio Shack.Mike N [last name deleted for privacy by Editor]
- Auburn, New Hampshire
A. Quick cover in NaOH, then etch with HClJake W [last name deleted for privacy by Editor]
- Frankfurt, New Mexico
RFQ: I would like to etch a small logo onto an aluminium part that has been anodized (yellow color). The etched logo could be gray or black/ other. Any leads? I live in the San Francisco Bay area.Peter K
aluminum sporting goods - Menlo Park, California, USA
February 26, 2008
Q. Dear sir, I want to etch a PCB made of 1.5 mm aluminium base and 35 mic copper clad.
In case if I use ferric chloride, the aluminium will not get affected?
manager - Chennai, Tamil Nadu, India
March 6, 2008
A. 50% caustic soda solution with water will do a very good etching for aluminum. the free caustic soda conc. should be 10 oz/gal.Oscar Fernandez
- Modesto, California
March 30, 2008
A. Try Spiderspit. This is a guy in Texas that has a product that is specific for etching aluminum. I just did a search and couldn't find it but I know it is called Spiderspit.david dahle
- Farmington, Connecticut
May 27, 2008
Q. I want to know how to etch aluminum for PCBs. I've tried to do it with CuCl2, but failed. I have to get 75-mic fine pattern. Please show me how to etch aluminum.JK.Sung
April 20, 2009
A. For etching on Aluminium try these formulations --
1) Distilled water 380 ml, +HNO3 10 ml, +HCl 6 ml, +HF 4 ml.
(Caution-except distilled water all the rest of the chemicals are corrosive acids. Always add acids to water and not water to acid.
2) Distilled water 200 ml, +ferric chloride 10 gms., +hydrochloric acid (HCl) 100 mls
3) Phosphoric acid---80%
Acetic acid -- 5%
Nitric acid -- 5%
Distilled water -- 10%
4)Copper sulphate-- 10 gm (CuSO4)
Sodium chloride ---5 gm
Distilled water -- 100 ml.
Take care while handling. use rubber protective gloves [linked by editor to product info at Amazon]
- Amravati, maharastra state, India
Ed. note: Please see the "thumbs down" entries below about the use of hydrofluoric acid.
May 5, 2009
A. I haven't tried the approach explained in
homepage.usask.ca/~nis715/salt.html but I read the article in detail, and it should work as explained:
The solution used there is:
CuSO4 (copper sulfate -- bluestone) 1 kilogram
NaCl (sodium chloride -- table salt) 250 grams
NaHSO4 (sodium bisulfate -- Sani Flush ) 25 grams
H20 (water) - depending on bath strength 10-20 liters
This can be compounded dry and water added to use. It contains far fewer dangerous components than other mixes I have seen. Advice is given for replenishing the solution, and disposal is bio-friendly and safe for drains.
The process takes advantage of the electronegativities of copper and aluminum (or zinc) to create a replacement reaction which removes the aluminum. All of the materials can be obtained easily and cheaply.
Ed. note -- Unfortunately, the referenced URL no longer exists.
Readers: when possible, please try to include an article name, author, or other clues to find an article when referencing it because web links often break within a very short time.
August 30, 2009
A. I had the privilege of studying printmaking at the University of Saskatchewan (some 10 years ago, 4-yr BFA) while Nik Semenoff (author of above recipe) was the artist in residence there. While I studied mostly in waterless lithography and serigraphy, I have printed at least a half dozen editions using the aluminum etching technique described above. I can verify that it works exceptionally well! Nik's email address is included in the above paper (not sure if it's still valid), but if you experience problems I would encourage you to contact him. The man is a genius.Jon Anderson
- Saskatoon, Saskatchewan, Canada
Ed. note: Thanks for the author's name, Jon, with which we have been able to find his new website/blog at www.ndiprintmaking.ca/
April 25, 2010
So pleased to find Larry Stark's recipe in plain English! I lost my recipe. It works well to agitate the etch lightly with a feather while the aluminum is in the etch.Shirley Strano
- Eumundi Queensland Australia
August 13, 2009
Q. I've tried the copper sulfate aluminum etch recipes. While these baths do etch the aluminum, the copper plates onto the board in its place. Any suggestions on how to keep this from happening?
The copper either plates onto the board or it clumps and falls to the bottom of the tank making a mess. The copper can be removed with nitric acid but salt and/or HCl seem to etch unevenly along the grain of the aluminum. The phosphoric/acetic/nitric blends seem to work much better but are more dangerous, being concentrated acid with little water.Ken Serenyi
- Greeley, Colorado
May 3, 2010
I have read through this website and have seen that some printmakers use hydrofluoric acid (HF) and sulphuric acid (H2SO4 as part of the mordant brew to etch Al, Zn and Cu plates. DO NOT ON ANY ACCOUNT EVER USE HF which is so corrosive that it will dissolve GLASS. And there really isn't any need to use the extremely dangerous sulphuric (far more dangerous than other common mineral acids) either - there are plenty of other options.
A. Copper sulphate/salt are useful for safe etching and ferric chloride is also fine and not that dangerous. Be sensible when handling chemicals and you'll be all right. But for heaven's sake steer well clear of HF, which can do untold damage in the hands of a non-chemist.
Careful when using ferric chloride to etch Al - it might explode in your face, so do tests outdoors to start with. Excellent for spit biting! Caustic soda ditto.
- Edgware, Middlesex, United Kingdom
September 13, 2013
A. While some of the more powerful acids, (Hydrofluoric), will etch Aluminum, a solution of Household Lye, (Sodium Hydroxide), diluted with distilled water will provide a much safer etch. A side benefit is that it will not etch most other common metals, Copper etc. A solution of hot approximately 100 Degree C. solution will remove all aluminum oxide very quickly. We used that solution when preparing aluminum electronic enclosures prior to Heliarc, TIG welding of the corners. It can be rinsed with plain cold water or a very mild vinegar solution. Water is best. That solution will burn you of course so wear good rubber gloves and eye protection. Respirators are usually not necessary if the etching area is well ventilated. You will know when it is not vented enough as the fumes will irritate your nose before it becomes dangerous.
Be VERY wary of Hydrofluoric Acid it is real bad stuff. Fir example if you burn the end of your finger your must immediately inject a Saline solution at 1/8 inch intervals all around the circumference of your finger 3/4 of an inch towards your hand. Otherwise the Acid just keeps burning away your flesh until your salty body fluids neutralize the acid. Bad Bad Acid!David Chisholm
- St. Louis, Missouri, USA
October 30, 2011
Q. Is it possible to make a aluminium nameplate by etching with caustic soda?
Applying the text with a laserprinter.
hobbyist - Holland
November 1, 2011
A. Hi, Ger.
Caustic soda will certainly etch aluminum nameplates. In fact, it is widely used to completely dissolve aluminum. But I would suggest getting some experience in using it to etch aluminum with other maskants or silk screening, to acquire a good feel for reaction rates, quantities, reaction products, etc., before trying to use laserprinted text as an etch resist.
Ted Mooney, P.E. RET
Pine Beach, New Jersey