Need a replacement process for etching aluminum

? 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,

A. Acid anodizes aluminum (forms aluminum oxide adsorbed on the surface). It is often faster to etch aluminum using caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] (NaOH). At least based on my experience.

A. 10% Nitric acid, 1% Hydrofluoric acid, and 89% Distilled water should do it :)

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Ed. note: Readers -- Please note the several "thumbs down" entries below about the extreme hazards of hydrofluoric acid.

"Artists Anodizing Aluminum:
The Sulfuric Acid Process"
by David LaPlantz

on AbeBooks

or eBay or

Amazon

(affil links)

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 --

Luck & Regards,

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.

A. caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] (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.

Hydrofluoric acid burns

Never use HF anywhere unless trained!
If you do, you MUST have the antidote gel on hand for instant use!

Calcium Gluconate
for HF acid burns

on eBay or

Amazon

(affil links)

!! 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!

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

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?

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?

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

Thanks & Regards,

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 ⇦ this on eBay or Amazon [affil links] -- 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 gloves ⇦ this on eBay or Amazon [affil links]

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Ed. note: Please note the several "thumbs down" entries below about the use of hydrofluoric acid.

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 sulphate ⇦ this on eBay or Amazon [affil links] -- bluestone) 1 kilogram
NaCl (sodium chloride -- table salt) 250 grams
NaHSO₄ (sodium bisulphate -- 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.

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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.

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.

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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/

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.

I have read through this website and have seen that some printmakers use hydrofluoric acid (HF) and sulfuric 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 sulfuric (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 ⇦liquid caustic soda in bulk on Amazon [affil link] ditto.

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 ⇦in bulk on eBay or Amazon [affil links] 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. 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!

A. Hi, Ger.

caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] 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,

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

Luck & Regards,