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topic 2076

Removing anodizing from aluminum

A discussion started in 1998 but continuing through 2018


Q. From time to time I have wanted to remove anodizing from aluminum parts. While I'm not certain what the precise nature of the surface treatments are, they're usually not hard anodized. I'm curious if there are any relatively simple ways, using readily available chemicals that can remove the treatments. While sanding and polishing do the job, it can be a very long job.

rob howard

"Surface Treatment & Finishing of Aluminium and Its Alloys"
by Wernick, Pinner & Sheasby
from Abe Books
info on Amazon


A. There are 2 ways to accomplish the removal of the anodic coating from aluminum depending on the surface you want to end up with --

A NaOH (caustic) etch solution will remove the coating but will etch the surface leaving a diffuse (matte) appearance.

The chromic acid/phosphoric acid solution used in the Acid Dissolution Test ASTM B137 [link by ed. to spec at TechStreet] will remove the anodic coating without affecting the underlying surface. The composition of that bath is 80 grams of chromic acid in 3.5 liters of water, add 140 ml of 85% phosphoric acid, add water to make 4 liters. The bath is operated at 190 - 200 °F. Immerse the part for 15 minutes and then rinse well in water.

Lee C. Branch
Richmond, Virginia


A. Would not a deoxidizer like 50% nitric do the job?

Bob Morrison
Ormond Beach, Florida


When aluminum alloys are etched (in caustic soda), the copper and other alloying materials are not dissolved/removed -- which will leave the surface grey or black. Nitric acid is often used as a de-smutter (sometimes called "de-oxidizer") to remove the remaining traces of copper after the aluminum has been etched. Different desmutting chemistry may be required depending on the other materials in the aluminum alloy in question.

January 2014

Hi Bob. To my knowledge, no, nitric acid cannot remove anodizing.

As a semantic issue, although this step is often called "de-oxidize" it seems that it would be better for us to call it "de-smut" because 50% nitric acid is a very powerful oxidizing agent -- it's certainly not a de-oxidizer.


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


A. Doesn't anybody know that good old oven cleaner has just enough acid to remove most anodizing without pitting or discoloring the aluminum surface? It works, try it.

Ken Perrella
- Utah


Actually, that is not so. Oven cleaner is very caustic, and will remove anodize; but I have found it difficult to control, and makes for a really ugly resulting finish. Completely undecorative.

Tom Pullizzi
Falls Township, Pennsylvania


A. I used oven cleaner on my oxidized frame on my GSXR and it didn't remove it. I sprayed it on and let it sit for 15 minutes and it did absolutely nothing. Sanding has been the only thing that will work.

DAVE L [last name deleted for privacy by Editor]
- BRISTOL, Rhode Island, U.S.



Oven cleaner DOES work quite well. But Anodizing is the second hardest substance known to man, its going to take longer than 15 minutes! I recommend at least 45 minutes, after that you will actually see the anodizing fall off. And depending on the aluminum underneath, it sometimes does leave a horrid finish. But for a Motorcycle, since I am assuming you were polishing the frame on the GSXR... the resulting finish would NOT matter because the plan is to sand, cut and polish. I am sorry you spent the whole weekend sanding off the Anodizing, if you had given the oven cleaner another half an hour, you could have saved some elbow grease.

Steve Callen
- Walton, Kentucky, USA

To minimize your searching efforts and to offer multiple viewpoints, we've combined some threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.

Which anodize stripper will not etch aluminum?

2001 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I have some highly polished anodized fittings that a client wants stripped, and a new decorative anodized colour re applied. What is the best acid/alkali solution to use so as not to etch the alloy in any way? In what ratio should the stripping solution be mixed?

Kind regards,

Steve Power
- Nelson, New Zealand


A. Although caustic soda is a popular stripping agent, it does not meet your requirement of not etching the base material. Rather, what you will want is the chromic-phosphoric mixture described by Lee Branch above. Good luck.

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


A. We have had some success using a mixture of phosphoric acid (35 mL/L), chromium trioxide (20 g/L) and water to strip Type I (chromic acid), Type II (sulfuric acid) and Type III (sulfuric acid/oxalic acid) anodize coatings from aluminum. The solution is heated to 100 °C and usually takes less than 15 minutes to strip the anodize. Unfortunately, it smuts the base aluminum, to varying degrees, when it has been anodized in Chromic Acid.

Teddy McCracken
- Blacksburg, Virginia, USA


Q. We use the chromic- phosphoric acid solution for anodizing & Alodine coating stripping. But I search throughout and can not find any method to analyze the components of tank solution. Could anybody give any information or help?

hong huming
- xiamen china

2001 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I am seeking a way to strip the anodic "Anodized" layer from previously anodized aluminum. I will re-anodize these parts after they are stripped. Any help would be greatly appreciated.

Craig Calhoun
- Houston, Texas


A. Dear Sir,

To etch the anodised layer from the aluminium, you can use a mixture of 50-100 grams phosphoric acid (85%) and 30 grams chromic acid in one liter water. Five to 30 minutes, then thoroughly rinse afterwards. First try a dummy before you put your sample in. Another one: a mixture of 50 - 100 grams phosphoric acid (85%) and 50 grams sodium bichromate in one liter water; Same time. These mixtures don't attack the underlying Al, but the surface may become dull. Watch out for the phosphoric acid.

Martin Saille
- Ghent, Belgium


A. Martin neglected to mention that the chrome/phosphoric mixture should be heated to 175 °F. I have not used the other mixture, so I'm not sure as to the parameters.

Marc Green
Marc Green
anodizer - Boise, Idaho

Pure Lye


A. Craig,

I don't know how helpful this will be but from personal experience, if you're looking for a simple stripper, a caustic soda such as Red Devil lye has worked for me. WARNING! Lye will dissolve aluminum so if you're going to give it a try, keep a close watch on the parts as they're stripping. Be sure to COMPLETELY rinse all parts in Distilled or DI water after stripping. Also keep in mind that this will etch the surface of the aluminum and you may need to clean the part (with a weak solution of Nitric acid) prior to anodizing. This is just from personal experience. I can't say weather it will work for you but it has worked for me in the past.

Hope I was of some assistance.

P.S. You may want to test this procedure on scrap before you try it on anything important.

Erik Knifer
- Great Bend, Pennsylvania

August 21, 2009

A. Use oven cleaner. It works wonders ... fast!

Jared Beck
- Pearland, Texas

How to strip anodizing from automobile trim?




- Hubbard, Ohio


Q. I am restoring a 1963 Chevrolet 2 door hardtop Impala. I have been able to clean and shine all of the chrome and steel, but am unable to clean the anodizing from the aluminum trim. I have buffed some of the trim, also have tried to clean and shine, but it will not come back to a good shine. Does anyone know how to remove the anodizing from the aluminum trim? I would be grateful for any suggestions.

R. Gerald Scales
hobbyist - Bowdon, Georgia


A. Whereas it is somewhat practical to strip copper-nickel-chromium from automobile parts and then polish and replate, it is NOT, repeat not practical to strip the anodizing. The anodic oxide is 1/2 into the metal and 1/2 on top of the metal. When you strip it you lose the polished finish. Now you can re-polish to a shine, and bring down a 10 to 11 step anodize process cycle and re-anodize. I have never heard of a job shop that will take in this kind of work.

To strip the anodic film, dip in 6 oz/gal Sodium Hydroxide for about 3 to 5 minutes,rinse in cold water, then remove the smut in 30% NItric Acid, rinse in cold water. Good Luck ! Take two aspirin and call me in the morning.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina


A. Hello,

The cheapest and in your case probably the best solution would be to use sodium hydroxide (aka caustic soda) solution. Its fairly inexpensive right now for the raw product (prices tend to dip and spike every few years, right now they are coming down from a 150-200% price spike).

Use this in a concentration of 5-7% of solution and see how it works. Be watchful of the process though, leaving parts in unattended will destroy them. Most parts such as car trim should probably strip completely down within 2-3 minutes. Heat this solution to 150F+ and you'll be fine. Use a polypropylene tank to keep it in as that has a heating max of 200F, where the cheaper plastic will start to flex and warp around 140F. Use a clean, room temp rinse tank to clean this off the parts, and get ready to buff and finish them off.

If you think things are taking a bit too long, bump the concentration by 1% at a time, anything over 10% is probably going to be nothing more than overkill and you'll just end up a lot of undissolved product at the bottom of your tank.

Good Luck,

Matthew Stiltner
plating company - Toledo, Ohio


Q. I am an amateur motorcycle enthusiast in need of some advice/insight. I recently purchased an 89 gsxr-750. The swing arm has already been stretched 6 inches and chromed. I would like to polish the frame of the bike, but I do not know what to do to get that annoying anodized coating off. Also would you recommend wet sanding the frame after stripping the anodized coating? I started working on a 6 inch section of the frame where the fairing will be covering just in case I botched it. At least this way I can cover it up. Any advice would be greatly appreciated.

Jamie Dalmida
Hobbyist - Boynton Beach, Florida, United States


A. I've used oven cleaner to remove anodizing on different bicycle components. A pair of Sugino cranks and a pair of DA hubs. The oven cleaner (Zipp professional) took it off of the cranks in a few minutes. it took a lot longer and more 0000 steel wool [linked by editor to product info at Rockler] to get it off of the hubs. I don't know if the coating on the hubs was thicker or if they had used some kind of sealant, but there was no mistaking the difference in time it took.

John McComb
- Oakland, California

September 16, 2008

A. Use a phosphoric acid bath at about 20 precent phosphoric acid to 80 precent water (1 gal. of acid to 4 gal. of water ratio) heat liquid to 190 degrees. Then submerge part depending on size for 1 to 3 minutes.

I'm an anodizing line operator.

Justin Ridenbaugh
- Newark, Ohio

December 29, 2010

A. I have read many articles on this subject and one stated that they took all of the anodized aluminum on their antique car and dipped it in drain cleaner for about 15 minutes to remove the anodizing. After cleaning and polishing it was coated with a clear plastic spray paint. The pictures of the finished product looked great. I am about to do the same thing to my car trim and hope it works. I would try the acid bath someone talked about but not sure what and where to buy this.

David Bennett
- Nashville, Tennessee USA

January 6, 2012

A. I read a bunch of these forums and found that the only thing that worked for me was Greased Lightning and elbow grease with a sander. Only after that can you really polish anything. I've included some photos on my Honda CX 500 build blog of my process here:

Matt Heckroth
- Denver, Colorado, USA

March 10, 2012

Q. I have a brass-tone anodized finished shower frame. I want to strip it and have a plain aluminum frame. What would you suggest?

Ira Boren
- Los Angeles, California

January 2014

A. Hi Ira. The caustic soda or oven cleaner should work, but just removing the anodizing doesn't necessarily mean it will be attractive, and it's a big job with hazardous chemicals, with little reward. Good luck.


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

January 3, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I have an Aluminum shallow cup 50 grams. It is already in anodised condition. I have to remove the anodized layer. Please give me a proper process. How to remove hard anodising from aluminum material.

gosai jaydip
heat engineering works - Surat, gujrat, India.

January 22, 2014

A. You can use 70 gpl caustic solution at 60 °C to strip the anodic film. Be careful, as the reaction is exothermic, creating fumes. Then you have to rinse in water and then neutralize the part in 200 gpl sulphuric acid or nitric acid solution, and then rinse in water well.

Timur Ulucak
- Istanbul, Turkiye

June 24, 2015

Q. I have to remove a Type 2 anodize coating off one side of the aluminum but leave the other edge coated with anodize. I can't put the entire part into an immersion tank because I can't strip all the anodize off. Would wiping oven cleaner on this edge with a rag be my best method?

Tom Beine
- Broomall, Pennsylvania

A. Hi Tom. Oven Cleaner is usually considered an amateur rather than a professional approach because it was neither made for that purpose nor do you know what is in it -- which leaves you with a lot of 'splanin' to do to your customers about how your quality control system works, and to your employees and the regulators about how your safety program works.

Depending on the particular parts, an alternate and perhaps preferable approach would be to mask the components either for one-side anodizing or for one-side stripping. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

REACH-compatible removal of anodizing

August 12, 2015

Q. Stripping of anodic coatings is done by either pickling solutions (acidic or alkaline) or with chromic/phosphoric acid solution. The latter having no influence on part tolerances.
In Europe,the REACH legislation will prohibit the use of chromic acid as of 2017.
My question therefore: does anybody know whether there are non hexavalent chrome containing solutions that work the same as the chromic/phosphoric acid stripping solution. i.e. no influence on tolerances?
Or is work being done to find such an alternative stripping solution?

Arnold Langeveld
Fokker Aerostructures - Papendrecht, Netherlands

simultaneous August 17, 2015

A. Hi Arnold,

I have been involved with the Chromium Trioxide Authorization Consortium (CTAC), which has applied for authorization for the use of chromium trioxide in Aerospace. If you visit the ECHA website you can see that it is up for public consultation at the moment. You can check that this use scenario is covered (I am pretty sure it is). Alternatively you can check with your CTAC representative (Fokker were at least originally part of CTAC) to look a the detailed dossier to check that the use scenario is covered.

If the authorization is granted we are hoping to have up to 12 years more to find replacement technologies. The sunset date of September 2017 looms large, but hopefully we will have a little breathing room to find replacement technologies after the sunset date has passed, otherwise I think EU based Aerospace will be crippled.

At the moment I am not aware of a stripping solution that works like chromic/phosphoric, with no loss of dimension and no attack of base material. The only thing I have been looking at is caustic based and this is nowhere near an ideal solution, the danger of attack of the base material is too great for my liking. Hopefully someone out there has the solution to your problem, but I am not hopeful at this stage.

Brian Terry
Aerospace - Yeovil, Somerset, UK

August 19, 2015

I answered this one a few days ago, may have gotten lost in the shuffle while Ted was sipping drinks with umbrellas in them on some beach.

Yes, there is a non hex-chrome anodizing stripper available, at least here in the states. It's sulfuric acid based, and has similar operating parameters as the chrome/phos strippers. We're only in the testing phase of this product, and have not put into production as of yet, but it does work quite least on a small scale.

I do not know how the shipping stuff would work from North America to the Netherlands. Ted generally discourages product links in the forum. So if I can get your email address via Ted, I could give you product and contact info.

Marc Green
Marc Green
anodizer - Boise, Idaho

August 2015

Thanks Brian. Thanks Marc, I sent you Arnold's e-mail address; please contact him privately with your sourcing info.

But, Marc! I most certainly WAS NOT sipping girlie drinks on some beach! I was washing down fried bologna sandwiches with draft beer at Robert's Western World in Nashville -- arguably the very best bar in the whole world, especially when Eileen Rose is So Lonesome She Could Cry and Rich Gilbert is shredding Ghostriders ...

You DO see why I couldn't hurry home, right?


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

March 12, 2016

Q. Where do I put the stripping tank for cleaning the Color anodize profile in Aluminum anodizing plant -- before the caustic tank or after the caustic tank? How to manage low Aluminum content in stripping tank.

Manauwar Azam
- Kuwait Salmiya

June 10, 2016 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear All,
How can you strip your anodized re-works (6063-6463 series)?
Do you use normal weak NaOH (60-65 gr/lt NaOH at 50-60 °C) or chromic-phosphoric acid mix? Which is better? We use the first but want to try second. Is there a use for the second one?

alaattin tuna
- sakarya,turkey

June 23, 2016

A. Hi Alaattin,
A Sodium hydroxide solution will indeed strip off the anodising from the aluminium parts.
But, with Aluminium being amphoteric, i.e., it reacts with acid and alkali, the sodium hydroxide will carry on dissolving the aluminium under the anodic layer once that has gone. This will be a fast and violent reaction at the temperature and concentration you have stated.
Therefore you will have no control over the amount of metal that is removed. It would not take long to completely dissolve the components.
So the chromic acid and phosphoric acid solution is the best option. This solution will only remove the anodic layer. It takes about 30 to 45 minutes to remove the anodic layer and there is no violent reaction during the process. The aluminium underneath will be unaffected by the acidic solution. The concentration should be phosphoric acid at 35 ml/l, and chromic acid at 20 g/l, heated to boiling, It will not work even if only a few degrees cooler than that. But it does work well when performed as described.
Good Luck

Mark Lees
- Fog encircled rock in the irish sea

January 9, 2017

Q. I found Marc Green mentioned a non hex-chrome anodizing stripper which also will not attack the base material. Can I get more information on it?

Actually I also have a additive formula of de-oxidizer (or De-smut) with contains HNO3 and H3PO4. If I place my sample with ~10-12µm Al2O3 thickness can the de-oxidizer remove the anodized layer with a prolonged time without attacking Al base? The solution contains 250 cc/L 65% HNO3 and 500 cc/L 85% H3PO4.

Andrew Wong
- Hong Kong

January 15, 2017

A. My ears must have been ringing. It's Sunday, so I'm not at work. I'll try to remember to get the name of the stuff tomorrow. We have used it with success, but not extensively enough to be able to completely recommend it. But it does work. Due to the nature of my customers, changing an existing process can be quite a challenge.

That being said, the manufacturer is not a supporting advertiser on this site, so I'm not sure if I'll be able to post the product name.

Marc Green
Marc Green
anodizer - Boise, Idaho

Ed. note: Please post it Marc, it's no problem! We don't want to interfere with learning, just to discourage spam and avoid opinions which lead to heat rather than light: "Iridite is better than Alodine" (or vice versa), "Atotech is better than Enthone" (or v/v), and to discourage those people who aren't really looking for camaraderie or offering help, but just constantly prowling the site for topics where they feel justified trying to advertise their products for free :-)

As my always insightful partner Tom observed at the dawn of the internet: "The Price/Demand curve for Internet Advertising: Infinite demand at zero cost / zero demand at infinitesimal cost" -- Thomas J. Pullizzi, 1995 :-)

Less Damaging Stripper for Anodizing Racks?

May 19, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I am looking for an alternative parts, racks and clips stripper. Have been using Etch and it's just eating the metal more than we would like. Was told about a proprietary rack stripper (AN775 by Stone Chemical).
Does anyone have any experience with them? Does anyone have other ideas or solutions? any input would be greatly appreciated.

James Dunne
Coatings - Kalispell Montana USA
  ^- Privately contact this inquirer -^

May 2017

A. Hi James, even such authoritative tomes as the previously-mentioned 1200+ page Wernick, Penner, & Sheasby tell us to either use titanium or titanium-clad racks, or suffer the wear & maintenance of caustic stripping of aluminum :-(

But we appended your inquiry to a thread which addresses a chromic-phosphoric anodize stripper which is non-etching. Whether it does a good job on rack stripping hasn't been discussed on this site yet, but maybe now it will be :-)

I am not an anodizer, but my suspicion is that consumption of raw aluminum rack components by the caustic is a smaller issue than their consumption by the anodizing process, such that improved rack strippers may address the round off error rather than the heart of the problem; even if the stripping removed no aluminum, the next anodizing cycle consumes raw aluminum to build the anodic film which you then remove, and "rinse and repeat". Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

May 23, 2017

A. Chrome/phosphoric strip will minimize the loss of aluminum but may be an environmental issue. This can also be accomplished by removing the racks from the caustic strip as soon as they are bare. Of course that takes some babysitting. Leaving them too long or forgetting them in the caustic will result significant loss.

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.
supporting advertiser
International Hard Anodizing Association - Wadsworth, Ohio

luke engineering banner

May 25, 2017

Well, it only took me 4 1/2 months (sorry guys, I spaced this off), but the product I was referring to earlier is Stripper 5275, from SIC Technologies (

It's a non-chrome stripper. I played around a bit with it on a small scale, and it does work as advertised. That being said, we decided not to facilitate it (limited space for an additional tank and ventilation), so my experience with it is limited. I do not know how long the bath will last. It seemed to take a long time to remove the anodizing, however with increased heat and concentration, the time shortened up. We never spent enough time to optimize the process.

It was pretty viscous, and had a sweet smell, I would guess it was a phosphoric/sulfuric acid based chemistry.

Marc Green
Marc Green
anodizer - Boise, Idaho

May 30, 2017

A. We used caustic-based formula for stripping anodizing racks for 3-4 years; later we gave it up. But we did not try either phosphoric/sulfuric acid or chrome/phosphoric based formula because of environmental issues.

At first we viewed stripping with a hand grinding machine (pneumatic) suspiciously. But we saw it as easier, faster, and faultless. So, we have used this method for 2 years now ... if I were you I would at least try this method, I advise everyone.


alaattin tuna
- TURKEY, sakarya

December 23, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Please let me know the method to clean the surface of aluminium sheet of thickness of 0.28 mm [0.011 inch].
Here cleaning means removing dirt or oil or grease or ink and as well the top layer which is anodized.


Parthi sethu

December 2017

A. Hi Parthi. We appended your inquiry to a thread which offers at least 4 methods: oven cleaner, caustic, chromic-phosphoric acid, or sanding. Please introduce yourself and your situation so people can advise you which is most appropriate, least dangerous for you, and most environmentally friendly. Telling us that the sheet is this thin is of some help, thanks, but it doesn't tell us whether you are a hobbyist with one old piece of dirty aluminum, or a process planner with acres of aluminum sheet to strip the anodize from every day, and the bestr stripping method also depends on what you intend to do with the aluminum next -- re-anodize it, paint it, clearcoat it, etc. :-)

Good luck, and Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

March 7, 2018

A. To remove anodized coating from automobile parts, build some troughs using 10 inch pvc pipe about 8 feet long. Cut an open slot about 90 inches long, and about 8 inches wide out of one side put a drain in the end, also close off both ends with a cap.
Using a 5 gallon bucket of water, add about 8 ounces of caustic soda slowly while stirring.
Pour this solution into your trough, then place your parts inside. After a few minutes it will look like it is boiling as it removes the coating. Most parts need about 20-30 minutes, but some take longer. KEEP A CLOSE WATCH ON THEM, IF LEFT TOO LONG IT WILL EAT INTO THE PARTS.
When finished, remove parts, rinse quickly with water, then brush off immediately, this will remove the black coating. Then buff to a new looking finish. Drain liquid into bucket, and re-use at any time. More acid^caustic will be needed if used several times. I DO THIS ALL THE TIME -- IT WORKS PERFECT.

Dean Lawson
- Mooresburg Tn. usa

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