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topic 22035

Need a replacement process for etching aluminum



A discussion started in 2002 and continuing through 2018 so far.
Adding your Q. / A. or Comment will restore it to the Current Topics page

2002

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


2003

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.

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


2003

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


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


2003

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 hydrofluoric acid.



2003

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
outdated


affil. link
"Artists Anodizing Aluminum: The Sulfuric Acid Process"
by David LaPlantz
from Abe Books
or
info on Amazon

A. Hi Peter. There are many different ways to etch and color a logo. But one of the most attractive is two-tone anodizing. The logo can be black or any color you like. An advantage is that everything then is the same material & finish so there are no concerns about adhesion or chipping or some chemical removing the logo. Please take a look at --

Thread 48706, "Two-Color Anodizing" for some very pretty examples.

Luck & Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



2003

affil. link
Cabosil
(fumed silica)

Q. We have an aluminum etching process where our operators mix Hydrochloric acid (37%) and cabosil =>
to form a paste. The paste is then brushed over the surface of the aluminum. The paste stays in contact with the aluminum for 8 minutes and then is rinsed off with water. The process is performed in a booth and the operators are required to wear full face air supplied respirators and acid suits. Is there a safer alternative for etching aluminum, that will give a similar degree of etching? Another chemical we can use rather than HCl? Our pieces we work on vary in size from small brackets to large (up to 16') panels of aluminum.

Thanks in advance for your assistance.

Todd Wegenast
- Melbourne, Florida, USA


2003

A. Hi Todd,
Some shops would use an immersion in a caustic tank rather than an acid etching slurry. I don't, however, know if it is practical to dip your parts, and you might have to de-smut them after etching.

Unfortunately the word "etch" is problematic. Some people say they want to "etch" aluminum when they want to bring out the grain structure for metallographical examination; others say they want to "etch" it when they want to give aluminum a matte appearance similar to a bead blasted finish; they say they want to "etch" it when they want to engrave lettering into aluminum or make printed wiring boards; some say they want to "etch" aluminum when they want to completely remove the aluminum in areas to make shaped parts, similar to water-jet cutting, etc.

So, I need to ask why are you "etching" the aluminum; in different words, what are you actually doing to it, or achieving in 'etching' it? Thanks.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



2004

Q. We are trying to find an alternative to etching this way as well. The finish we are getting is too dull. In order to get a shiny finish we have had to switch to stainless steel. Is there any way to get an etched look without the white chalky residue?

Laura Burkholder
Nameplate and domed labels - Arlington Hts, Illinois, USA


2004

A. Caustic soda (sodium hydroxide) is commonly used in the industry for etching aluminum. As indicated by Mr Ted Mooney, the parts will have to be desmutted/deoxidized. Dependent upon the concentration, temperature, bath age, and metal loading, the etch rate of caustic on aluminum will be affected, but it is normally quite slow and the depth of etch is fairly shallow. The end use, or post process, i.e. chromate conversion, bonding, paint, will determine the type of topography you will need to create on the part/s. Alternate acidic etchants based on ferric or cupric chloride can be used. In the chemical machining industry the etchant most widely used is ferric chloride. The same basic parameters of concentration, temperature, metal loading, etc. will also influence etch rate. Please note however, that the etch rate of ferric versus caustic is many times higher and tests to determine the etch rate for a specific set of parameters should be determined. As with caustic, ferric etching will cause a smut to form on the parts which will have to be removed. A very effective desmut and bright dip solution can be made as follows:

D.I. water - 95% b.v.
Concentrated nitric acid - 2.5% b.v.
Concentrated hydrochloric acid - 1.5% b.v.
Concentrated Hydrofluoric acid - 1.0% b.v.

Temperature - ambient
Dwell time - ~ 1 minute
Please note! Please read MSDS's for all acids, paying careful attention to handling, protective gear, storage, and disposal instructions. These acids are nasty but very effective at performing the desmutting and bright dip step of the process.

Ferric chloride is very effective on stainless steel as well. It will require a higher concentration and longer dwell time. The smut that is formed is very tenacious but can be readily removed using a modified version of the acid desmut chemistry as described above. A 1% - 2% addition of hydrogen peroxide needs to be made to the acids. Compensate for this addition by reducing the water concentration accordingly.

Wade Rohland
- Ramona, California, USA


affil. link
Calcium Gluconate
for HF acid burns

2006

!! Just a word of caution, Hydrofluoric acid (HF) is very dangerous. It is unlike other acids, in that, after exposure, not only is the immediate first aid important but also monitoring of Calcium levels in the blood. Fluoride ions penetrate through the skin and bind up calcium forming an insoluble salt. An exposure of a 50% solution over an 8" x 8" area can be deadly! Keep Calcium Gluconate =>
on hand and by all means read the MSDS!

James Brock
- Newport News, Virginia


2006

thumbs up sign Thanks for the very important note, James. The dangers of HF are in a whole different category than most other acids.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



affil. link
Ferric Chloride

2004

info 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


February 26, 2008 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

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?

muthusamy v [last name deleted for privacy by Editor]
manager - Chennai, Tamil Nadu, India

----
Ed. note: We appended your inquiry to this thread so you can see that the aluminum certainly will be affected, Muthusamy :-(


February 26, 2011

Q. I tried etching aluminum with ferric chloride and even a small amount bubbles up and steam/smoke comes off the metal. I got the ferric at Radio shack. I am using 5150 aluminum. Am I doing something wrong or is this typical for the process. What are the gases that are emitted? Are they dangerous?

Tracey Johnson
- Bloomington, Minnesota, USA


2006

info Quick cover in NaOH, then etch with HCl.

Jake W [last name deleted for privacy by Editor]
- Frankfurt, New Mexico


? You might be right, Jake, but I do not understand what you are saying: "quick cover with NaOH"

Thanks & Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



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
- Korea


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 Rubber Gloves [affil. link to product info on Amazon]

sudhir pitale
- 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.

Larry Starks
Tampa, Florida

----
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, and other clues to help readers find the article when referencing it because your web link will usually break in a very short time whereas this site has been trying to be a permanent reference for 30+ years.


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

thumbs up signSo 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

thumbsdownI 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.

Manfred Welling
- 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.

thumbsdownBe VERY wary of Hydrofluoric Acid it is real bad stuff. For 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.

Ger Wit
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.
Good luck.

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


November 19, 2016

affil. link
Calcium Gluconate
for HF acid burns

thumbsdown 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 it 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%. I don full PPE and rely on engineering controls such as equipment design and ventilation. In 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 [with the extreme urgency of] 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 Aluminum

November 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.

Thomas Utley
Restorer - Tucson, Arizona, USA


A. Readers, you can search the site for related topics or see the following closely related topics:

Thread 1953, "Paint/color filling etched metals"
Thread 14847, "Safe acid etching of aluminum"
Thread 40756, "Laser etching of anodized aluminum"
Thread 45834, "How to print patterns onto Anodized Aluminum"

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

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