Removing Anodizing From Aluminum Quickly and Easily.

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.

Step 1: Materials.

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!

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.

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.

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

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.

Comments

[Ahusick]

What else can be used other than Greased Lightning, like ZEP Industrial Cleaner/Degreaser?

Any others proved to be equally adequate?

[daniel_reetz]

It's been a while since I have used this method - it's likely that other "purple" cleaners will work. The key is that they contain a detergent and a small amount of sodium hydroxide (see my previous comments). Sometimes, you can get the info on ingredients from the SDS (Safety Data Sheet) or MSDS (Material Safety Data Sheet).

[Ahusick]

Thanks Daniel,
Am having trouble finding Greased Lightning, plenty of other similar products.
Some that I know would work because they contain Sodium or Potassium Hydroxide. However they go so far as to say Do Not Use on Aluminum. If exposure is limited to say 10 minutes then washed off, I'm thinking it'll be OK.
I need to un-anodize four center caps off my aluminum/alloy wheels so that I can polish them to a mirror finish.
The SDA or MSDS sheets might mention the Hydroxide but neither so on to state the concentration or percentage concentration.

[erik.savoie.3]

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.

[ChaimD1]

Correct Erik. All that this process with Greased Lightening does is remove the dye from the piece. It is still anodized, but the natural Aluminum color is what you 're left with.

[GmoTheChemist]

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 :)

[WayneC72]

GmoTheChemist,

I am looking for a way to remove the black and grayish coloring on some aluminum cookware that I simmered in plain hot water for a while to remove old dried food. Now I have another problem with trying to remove the black/gray areas (just in some areas of the thing aluminum pieces of cookware). Would a drain cleaner be appropriate or not. I don't want to end up with a rough surface after cleaning the black off.

Thanks.

[KenL22]

Useful info, but sometimes it is necessary to get to the SOFTER aluminum below the anodizing. For example the mounting rings for a rifle's scopes can sometimes slide back due to the force of the ammo being fired repeatedly. If the anodizing is removed and then the rings are remounted to the rail they are less likely to slide back over time causing the scope to no longer be zeroed in. Small area of aluminum oxidization right at the connection may actually help to hold it better. Aluminum oxide Al2O3 is insoluble in water, fairly hard and useful stuff once it forms around the joint, not as attractive or good as the if you could Anodize it but good enough.

[SyedN2]

Hey GmoTheChemist , Thx for the comment really help full, I am looking to de anodize a part to gold plate it , any more tips , like how long to keep in drain cleaner?

etc

regards

syed

[GmoTheChemist]

Hy SyedN2, unfortunately, aluminum is the hardest metal to plate on because of it's tendency to oxidize with the air (see point #2 above). To strip off the anodize, use the procedure above and you'll have to do the continuity test to make sure you removed all of the anodize. Time in the solution depends on how thick the anodize coating is. There is no real set time, it just all depends.

To replate, there will have to be some additional steps involved. The best method is to take it to a decorative plating shop and have them do it. They have the expertise to do it right the first time. Proper steps would be to clean/degrease the surface, deoxidize the surface using an acid step (50% nitric acid BE CAREFUL) and then the key part is you have to use whats called a "zincate" step. The zincate coats the aluminum with zinc hydroxide which protects the aluminum from the air so when it goes into the next tank, the plating will actually stick. After the zincate step it either needs a copper strike (thin copper plating layer) or an electroless nickel strike (thin nickel layer) you can plate the gold on top of the nickel.

I assume you wanted to try one of those home gold plating kits. I can assure you that they probably won't include the copper strike/electroless nickel strike or the zincate step. You can ask them if the kit can plate over aluminum but I would doubt it would actually stick. I would just take it to a plating shop.

Cheers,

GmoTheChemist

[SyedN2]

GmoTheChemist -

Yeah I see that now , I think I this would be a bit out of my league.

Was actually looking to gold plate my iPhone , why did thees things have to be made out of aluminum ! :P

I guess the crazy prices they charge for plating phones makes a bit more sense now.

I used to think it was a straight forward process.

You have been a grate help for me in understating some things I had no Idea about.

Thanks a lot! :)

Regards,

syed

[GmoTheChemist]

You could have it re-anodized in a gold color...It would still look pretty cool! We have a gold color here at our shop. I'm sure you could find one close to where you are located. :)

[RickRoll]

Hello, I wish to buy a knife that is cheaper than its other versions because it is coated with a rainbow finish, would anodizing the blade remove this finish? And also is there a coating that I can buy in order to give it a finish of my own i.e. black? Thank you

[NormanH2]

Should I read that the anodizing off the frame and rims

[NormanH2]

Kind of figuring this out I build motorized bicycles and I stripped the emerald eyes off my bicycle frame and rims wet sanded and polished my aluminum looks like Chrome and the wax seems to protect it pretty well from what I read you saying that mind frame and rims will deteriorate

[TomL19]

[jackowens]

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

[UncleB1]

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]

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

[UncleB1]

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.