A discussion started in 2002 but continuing through 20182002
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
? Hi Robert, hi Haiderali: In many instances caustic etching is more effective & appropriate than acid etching.
But before going down that path, can you please provide some context so that we can understand exactly what "etch" means to you? -- aluminum can be etched to reveal its structure for metallographics; or to provide a matte anti-fingerprinting look; it can be etched in patterns for lithographic/printmaking applications or for nameplates; it can be etched/dissolved all the way through to make shaped/hollow components. Different etchants and techniques will be preferred depending on the application. Thanks.
Ted Mooney, P.E.
Pine Beach, New Jersey
We need "Aloha" now more than ever
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: Readers -- Please note the several "thumbs down" entries below about the extreme hazards of using 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 HCl.Jake 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
Ed. note: Thanks David. But readers, please avoid brands and sources (why?)
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 note the several "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, but the article, "Using a Safer Mordant Intaglio Etching on Aluminum and Zinc", 2003, by Semenoff & Flint can currently be found on the Internet Archive at https://web.archive.org/web/20110228093716/homepage.usask.ca/~nis715/salt.html
Readers: if possible, please try to include an article name, author, or other clues to find an article when referencing it because web links usually break in a 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 °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 an 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.
Pine Beach, New Jersey
We need "Aloha" now more than ever
November 19, 2016
Due to my experience and the comments here I had to post this.
Stay away from HF!! HF is deadly. Not because it's caustic. It's actually a mild acid and it does not aggressively eat through everything like some sources and theater say. Its dangerous because it's a contact poison. You can badly damage nerves and or die of organ failure through relatively small exposure. The fluorine disassociates with the hydrogen for the calcium and magnesium your body needs to function. With HF the burn isn't what kills you and the death isn't short and sweet. Don't breathe it in, don't touch it, really it's best to just stay away from it altogether unless you really know what you're doing and have the equipment to handle it. BTW, exposures are treated with calcium gluconate in various forms designed for the different exposure types. The concept is that the fluorine ions will bond with the calgluc instead of what's in your body. You shouldn't have HF without also having calcium gluconate.
I service equipment designed around HF. Work with large quantity of %60. Don full PPE and rely on engineering controls such as equipment design and ventilation. If working with this stuff you really have to consider ventilation. If you catch a big whiff of it you need to seek immediate medical attention. In fact, if you or your business are working with it then you should really contact the nearest medical facility to communicate with them that you're working with it and make sure they are equipped with the knowledge and gear to react in an emergency. An HF exposure should be treated like a snakebite.
I take an annual safety refresher. The most recent they showed a youtube video that demonstrated the effects of HF on flesh. It is a good video because it quashes the flesh eating idea that some new HF users may have.
Stay safe people.J Brown
Glass and materials - Buffalo, New York, USA
Deep Chemical Etching in AluminumNovember 14, 2018 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. Hi all. I restore old machine tools like lathes and milling machines. This hobby often involves recreating etched machine nameplates. Etching depth for me varies from around 0.010" to 0.025" for ease of color infill afterward. Any shallower and it's tough to avoid scratching the color.
I have a reliable process worked out for recreating the artwork and heat-transferring laser toner masks to the metal. I've had really great results in brass using ferric chloride. It provides fine detail, very little undercut with the part facing down in the tank, and basically no fuss etch depth proportional to time and temperature.
Aluminum, however, is turning out to be a real challenge for me. Ferric chloride goes exothermic very quickly and melts the toner mask before I can get good depth. I've tried the oft-mentioned combination of hydrochloric acid and hydrogen peroxide, but it, too, generates too much heat for the depth I need. My mixture is approximately 4 parts drugstore hydrogen peroxide (3% concentration) to 1 part hydrochloride acid (85% concentration). Note: Online references suggest 2 parts peroxide to 1 part muriatic acid. My proportions reflect the fact that my acid is lab-grade acid at 85%, not muriatic pool shock at 35% from the home center.
I've had some good results in aluminum electro-etching in saturated saltwater, but the results vary widely. Small plates (1-2 in^2) etch relatively quickly but larger plates (20 in^2) only crawl with little to show after several hours of bubble generation. I connect the part being etched to the positive supply. I use a scrap of the same aluminum material as the workpiece on the negative lead. My power source is a 6 VDC automotive style battery charger that delivers up to about 8A. I suspect I'm limited by surface area vs. current flow but I confess I'm no chemist, just a mechanical engineer who skated through chemistry class on the way to the machine shop.
Is there a more reliable approach to etching fine details in aluminum for a hobbyist like me? Is my power supply the culprit? Does the aluminum allow matter (using 6061)?
Thanks for any advice you can offer for home/hobby use.
Restorer - Tucson, Arizona, USA
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