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Removing Anodizing From Aluminum Quickly and Easily.

Picture of Removing Anodizing From Aluminum Quickly and Easily.
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I dislike the color of many anodized parts and tools, and I love the look of bare aluminum. Fortunately, it's easy to remove the anodized coating from most things.

I first heard about this here, but I found their instructions lacking.

The pictures below show what we want -- and what we have.
 
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Step 1: Materials.

Picture of Materials.
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You need:

1. Some Greased Lightning Cleaner.
2. A plastic dish of some kind.
3. A brush.
4. Something with a coating that you just can't stand. I had a new folding knife which was a particularly nasty shade of olive drab.

Step 2: Go!

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If necessary, disassemble your knife/tool/object. You don't want to expose anything but the aluminum to the cleaner, if you can help it.

Remove the spray cap of your Greased Lightning.

Put your parts in your dish.

Pour some Greased Lightning in there!

Step 3: Scrub time.

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Scrub the parts with your brush.

Constantly agitate the solution.

Depending on the thickness of the anodizing, it may take a little while. My knife was HAIII -- which means that it has a thick layer of anodizing. It took about 15 minutes to get it totally clean.

Step 4: Admire Your Clean and Beautiful Parts.

Picture of Admire Your Clean and Beautiful Parts.
Remove your parts from the solution using a tweezers or hook. Run it under cold water until there are no more suds. Pat dry with a towel or paper towel.

Look at your clean, non-ugly parts. Great!

Oh bother. Now you have to put the thing back together.

Step 5: The Final Finish

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After reassembly (obviously only applicable if you first disassembled your object), check that everything works.

I think this thing is dead sexy in white. And after almost a year of carrying, it still looks great.

Hello, I am a chemist that works in a metal finishing shop and we anodize parts for aerospace and the military. I'd like to shed some light on this process but I would pose some questions and information first.
1) why would you want to take the anodize off? Anodizing protects aluminum from corrosion. Without the coating, aluminum will corrode over time (white splotchy appearance) and will ruin the whole purpose of the item being used. If you don't like the color, why don't you buy a knife with the color you want? or without color? You can get anodized Items without a color and have them still be protected.
2) Bare aluminum will protect itself from the environment by forming a very thin layer of aluminum oxide (which is the same component of an anodized surface) but that will hardly protect itself from corrosion.
3) Stripping the anodize will also cause the material to change dimensions. When you anodize a part, the bare part will be a little smaller dimensionally before it gets anodized. The manufacturer does this on purpose because they know that anodizing will increase the thickness of the part evenly on all surfaces. Removing the anodizing changes its dimensions by making it smaller and then you will get other problems like..
4) The sheath not fitting correctly and the hardware attaching the knife to the sheath not fitting correctly. The manufacturer designs the part with a very high tolerance (like within 0.0002") to make sure everything fits correctly. If the hardware attaching the knife is too loose (because you stripped the anodize) your knife blade might fall off when using it. Also, the sheath might not fit correctly and will cause the knife blade to be exposed to the environment which will cause the knife blade to corrode. All of these are bad.
5) From your pictures and notes you said it was "HAIII" which means it was Type III anodized or "hard anodized." Hard anodizing produces a harder more abrasion resistant coating than Type II anodizing ("regular" anodizing) but from looking at your pictures, the original sheath doesn't look hard anodized. Hard anodized coating will come out very dark. Depending on the alloy it will be dark brown or dark grey. Another issue is that hard anodizing produces smaller pores (look it up) that makes it very difficult to accept a dye color. Most of the parts we do here that are hard anodized will only accept a black color. Any other color makes it look weird. If the knife manufacturer said the sheath is "hard anodized" they are either lying or the coating is so thin, that its abrasion resistance will be the same as regular type II anodizing.

That out of the way, if you still want to remove the anodize, the best way is to use a drain cleaner of some sort. Drain cleaners have sodium hydroxide (caustic soda) and/or potassium hydroxide. **CAUTION! THEY ARE VERY NASTY AND CAUSE BURNS!!** Be EXTREMELY careful when handling these chemicals. When immersed, the part will bubble vigorously. You probably won't need to scrub if the drain cleaner is strong enough, plus that could cause the chemical to splash and you don't want that.
Once all the color is gone, if you just wanted to get rid of the color, you're done. Just wash off with PLENTY of water and dry it. If you want to remove all of the anodize layer, youre going to have to get a continuity meter/tester.
The aluminum oxide of the anodized layer is an insulator. This means it does not conduct electricity. A continuity meter checks if there is an electrical current flowing through objects. Attach the part you're checking to something conductive like steel or copper or maybe a piece of aluminum foil (make sure they are both touching). With the continuity meter clipped to the other metal, touch the tip of the meter to the part. If the light turns on, there is current flowing to the part and all the anodizing has been removed. If not, there is still coating on it and you have to strip it more.
You CANNOT re-anodize a part unless all the coating has been stripped off. You might be able to get the bare aluminum look (as opposed to the white above) if you polish the part again but usually it won't become bright and shiny again. Of course, you can always send it to a metal finishing shop and let the pros do it :)

Sorry for the long response but I like to educate :)

jackowens2 months ago

I too prefer the clean aluminum look, I never new something like this existed. Thanks for the tutorial!

erik.savoie.32 months ago
I don't thing you removing the anodized surface. It looks like your just scrubbing the dye out of the anodized surface, as anodized aluminum has large amounts of microscopic pores and that's what enables it to be dyed so readily. The aluminum oxide(anodized surface) is harder than most steels (that's why its used in most grinding wheels and sand paper), albeit very thin, and scrubbing with cleaner and a brush would not scratch through it.
UncleB16 months ago

Dan,

Just got a quick question for you. From what I could see in the picture, the brush didn't leave any scratch marks while removing the anodizing, but I still want to ask, did it scratch it at all? I'm working on something that I don't want scratches on. Hence why I don't want to use sandpaper.

Thanks.

daniel_reetz (author)  UncleB16 months ago
One thing you can consider, is using a plastic brush, which will definitely be softer than any metal or anodized finish. I got a pack of plastic bristle brushes from Harbor Freight for a couple bucks. In my case it definitely didn't scratch it all, but to be honest, I barely needed the brush. I'm still using this knife-- it's in my pocket right now and the scratches on it are fro sloppiness, not from removing the anodizing color. Good luck with your project, please let me know how it turns out
Will do. I was thinking of trying sandblasting first to be honest. I love the speckled finish afterwards. Either way, ill post pics when it's done.
TomJ28 months ago

Very helpful article and thread. Thanks a lot.

Tigertouf1 year ago

Hi Daniel,

I'm really happy to have found this instructable. Although I do have a question:
Once the dye is fully removed, can I just dye the aluminum another color?

I'm currently debating of deanodizing the alloy parts of an RC car chassis and change it to a different color. Could I just follow your procedure and dye it with clothing dye?

swander1 year ago

Tried liquid plumber, couldn't get Lye at grocery store at 8PM on a Sunday. Soaked my 1965 headlight bezels in the stuff straight and it didnt do squat. I soaked for another hour and the anodizing is finally starting to feather off with sandpaper. Fast, I wouldn't say that. Easily? Not with Liquid plumber and it did contain Sodium Hydroxide. So maybe I got some weak sauce...Ill soak overnight. Even a sanding flapper wheel on a die grinder didnt just wipe this stuff off!

Sodium hydroxide is also know as Lye, which is used to make soap and is also used in things like oven cleaner and other heavy duty cleaners. You can buy pure lye in flake form, used for clearing drains, at most hardware stores. Mixed with water, it will strip anodizing.
MrSquirrel2 years ago
Hey, sorry I forgot to report back. The Multi-Purpose did not remove the anodizing, but it did change the surface texture of the metal.
MrSquirrel2 years ago
I know this post is old, but I have one question. Can I use Multi-Purpose Greased Lightning, or do I have to use the Auto and Shop that you used?
daniel_reetz (author)  MrSquirrel2 years ago
I don't know - but please report back if the Multi-Purpose works for you.
tsyed12 years ago
Hello guys ... I know it is a very old post but may be someone can reply ... I hope daniel_reetz is still around :-)
As you might already heard about anodize coating on the back aluminium of black iPhone 5 is susceptible to scratches. I've already dropped it once and got nasty marks on the corners. I'm thinking about removing this black anodized coating myself. What is the best method to do that, considering that I can't dip it in something? It has to be removed neatly and completely. Another thing I wonder is would I get a nice silver aluminium (like MacBooks) or some greyish silver aluminium?
daniel_reetz (author)  tsyed12 years ago
That's a very interesting idea, but I have no good idea on how to do it. Even the mild solution I mention here is a bit corrosive, so you definitely don't want any going inside the phone. Perhaps applying it with a slighly dampened Q-tip could control the fluid enough to make it work. I can tell you this, it will take time. Good luck!
Thanks for replying daniel. Couple of more questions :-)
Would a mild solution have any effect on plastic parts?
You said "it will take time", are we talking about minutes or hours?
Your knife appears white after the treatment not silver, like aluminium, why?
One comment below said "I think what you really did was remove the dye, not the anodizing". Does that mean my phone's back might not actually become silver?
shenrie12 years ago
...or you could just use paint remover...I accidentally discovered this today D:
I just soaked grease covered anodized parts in Lestoil to remove the grease and tar. It started foaming after 10-15 minutes and after 30min it had removed the red anodized color. I'm not sure if it is just leaching the color or stripping the anodized layer. Does anyone have any idea how/why a cleaner like Lestoil would have this reaction? It seems weird that a grease cleaner safe enough for laundry and mopping would have the power to do this.
junits154 years ago
oven cleaner works well also, but its really nasty stuff
oven cleaner is terrible. a few years back on a news program here in sydney a lady got some on her skin and it literally ate away at her flesh. she had a good 2 inch deep crater in her calf muscle. it was terrible
spyderbyte4 years ago
I have heard that both drain cleaner such as Draino and oven cleaner will remove the anodizing on aluminum. I am re-finishing the aluminum trim on my antique automobile and have been told that once you have removed the anodizing the aluminum can be polished and then protected with a clear spray plastic sealer. I've seen the finished product and was impressed. Does anyone know what to use for the plastic sealer to maintain the polished look?
deega5 years ago
No need to scrub.  Just get some drain cleaner (sodium hydroxide), the granule type, and mix with water to whatever strength you desire.  Dip the anodized part into the solution for about 15 seconds and rinse with fresh water.
Great 'ible! I would have never thought that something like this was possible until i saw this. +4.5!
I think what you really did was remove the dye, not the anodizing. The anodizing is actually aluminum oxide - which if you look it up, is one of the various abrasives used in sandpaper etc - e.g. "it's hard". I don't think a simple cleaner removed it... of course I'm surprised it removed the dye, so I don't know for sure ;-D Anyway, it WAS an ugly color!
daniel_reetz (author)  sr1sws6 years ago
Actually, you'd be surprised -- you can remove aluminum oxide with pretty much any caustic. Most people use oven cleaner, which contains sodium hydroxide (lye). Just like you, I doubted that it would work -- so before I spent the money on Greased Lightning I called my dad (he's a chemist) and he assured me that any base should eventually destroy it. I can ask him for the reaction and post it here if you're interested. Might be a nice addition to the instructable.
Actually, reading the link you included, this process oxidizes the aluminum, which softens the anodizing. You need to sand and polish the aluminum to get rid of the white Aluminum Oxide.
daniel_reetz (author)  plasticbiker6 years ago
The first step in the commercial production of aluminum is the separation of aluminum oxide from the iron oxide in bauxite. This is accomplished by dissolving the aluminum oxide in a concentrated sodium hydroxide solution.

From my dad, a chemist:

"Aluminium oxide reacts with a solution of sodium hydroxide to yield a solution of sodium tetrahydroxoaluminate. Al203+2NaOH+3H2O --->2NAlOH4 "

The whiteness of this surface is due to the bead blasting that they did pre-anodizing.
daniel_reetz (author)  daniel_reetz6 years ago
Ah, Google is my friend. Here's the reaction with sodium hydroxide. I'll check the MSDS for Greased Lightning and figure out the active ingredient.
daniel_reetz (author)  daniel_reetz6 years ago
The MSDS (material safety data sheets) for Greased Lightning indicate that the active ingredient is sodium hydroxide. There's also a "proprietary surfactant" which probably increases the speed and efficacy of the reaction between the aluminum oxide and sodium hydroxide.

Sweet.
dchall86 years ago
I wonder if ammonia would do it...maybe take longer.
Scott_Tx6 years ago
You should note that the surface anodizing hardens the surface of the aluminum. Scratch prevention and all that. But aluminum is self anodizing on exposure to air so it'll eventually turn gray and take on light surface hardening again.
daniel_reetz (author)  Scott_Tx6 years ago
Good point. I did leave out the fact that it will self-anodize a little, and that this process definitely reduces the scratch-resistance of the surface. However, one good thing is that if you scratch the surface, the underlying material is now the same color. Hence scratches are much less obvious.
misformiche6 years ago
agreed. dead sexy... roar.