removing anodising

I’ve always wondered about a similar thing (but never asked), i.e., do you need to do anything to preserve the surface after stripping the anodizing, like polish or something?

Bare aluminum will oxidize in a matter of seconds when exposed to oxygen. Leaving a very thin layer of oxidization. Anodizing is essentially the same thing only with a much thicker layer and the ability to dye the honey cone shaped layer giving the aluminum the appearance of color. When sealed the color (dye) gets locked in those honey cone shaped formations.
No further treatment is necessary, it takes care of its self in oxygen. I would recommend that if you do polish aluminum that you a apply a coat of wax. That should help retain its luster longer and keep finger prints or water spots from showing up.

I’m looking into possibilities of modding a certain light to QTC twisty. But the light has anodized threads.
If the anodization is stripped off the threads, will the material loss make the threads work worse?

Have you a local machine shop that is equipped with a glass bead blast cabinet?

No chemicals involved, only a dust mask which we are already wearing

Have operator use recycled (extra fine) glass bead media… and important to use Low PSI on soft Al…

You can hand polish smooth machined areas if desired

Good luck!

Yes, you’re correct it would be hard to get ano completely out of knurling. You would still end up using chemicals to finish cleaning…

I made a DIY blast cabinet out of plywood and plexyglass. My compressor is a little small in CFM, so takes awhile but eventually gets the job done

Post some photos when you are finished

@Agro I think the threads will work equally with or without ano. Although I’d be concerned about some chemicals could eat up Al making the threads fit loose

Watch the Al surface isn’t overly dissolving… and open a window

Yeah, agitation swirling around in the solution… the plate shops do that automated when stripping metal parts in tanks

isn;t any chemical process going to leave the metal uneven, dull, and splotchy at the ‘end’?


Removing anodizing is easy.

  • Get a jug of Greased Lightning from your local hardware store.
  • Pour some into a large yogurt container. No need to dilute.
  • disassemble your flashlight.
  • insert the aluminum flashlight parts so they are completely immersed in the Greased Lightning. I like to stand the parts up. I use a long nosed pliers to position the parts.
  • let the parts sit. Depending on how fresh your Greased Lightning is it may take anywhere from one to twelve hours. Check it periodically.
  • once anodizing is removed, rinse the parts in water.

I have used drain cleaner (caustic soda) and it will remove it all even in the knurling. The mixture % will also be time related. Low % and it will take a long time.
I usually just keep adding caustic soda (mixing in, testing each time) until I see it slightly bubbling when the part is submerged. I wouldn’t go over board because your in a hurry though.
The reason most people prefer slow, low % is that the caustic soda is eating at the aluminum. If you leave it to long it will eat thru more than just the anodizing. Then it can cause fitment issue’s or mainly loose threads. The anodizing is like a tiny open top volcanic structure that is grown on the aluminum. Then when dipped in color (dye) it fills the volcano thru the top hole and then its dipped in a hot water bath or steam to seal the hole at the top of the volcano trapping the color inside. The color of anodizing is not the color of the actual aluminum its the color being traped in these tiny structures on the aluminum. The structures look more like a bee honeycomb than a volcano from what I have seen, I just thought the volcano would be easier to picture.
When removing anodizing your basically trying to break down the honeycomb, eating the structure away to release the dye. So moving and agitating does help. Slightly warm water seems to help for me also, hitting with a tooth brush to help release the dye helps also.
Once the anodizing is removed the aluminum will look dull depending on how long and the strength of the bath. Steel wool and some kind of metal polish will get it back to a luster. The knurling is a little time consuming.
During manufacture this growth of anodizing has to be figured in the machining process or matting parts will be too tight after anodizing. So its machined with more tolerence than normal, so remember that removing the anodizing takes it back to this over tolerenced machined state. Which is fine unless you leave it in the bath too long and its more than necessary. That’s why its inportant to use just the right amount of time soaking to remove the anodizing and no more than that. Otherwise its a easy process. :slight_smile:
And please be careful, its not as bad as a acid but in the eyes it could be very dangerous. You can read up on the dangers of caustic soda to help be safe.

That turned out very nice!

maybe i need to try it out using lights with damaged anodizing

  • Sodium Hydroxide: Also known as caustic soda or lye (NaOH), it is the most common method for stripping anodized coating. The concentration of caustic soda is generally 2-10% of 50% liquid caustic soda by volume in water. Depending on the bath concentration and temperature, the anodic coating should strip in a few seconds to a few minutes.
  • Potassium Hydroxide: Also known as caustic potash (KOH), this solution acts as a strong base (alkali) and reacts well with acids. It’s commonly found in drain cleaners, along with sodium hydroxide and sulfuric acid. It’s likely that, when applied together, this caustic etch solution will result in a matte appearance on the component.
  • Acid Etching: This process involves a mixture of chromic acid (CrO3) and phosphoric acid (‎H3PO4). The end result will probably look the way it did before the aluminum was anodized, as this chromic phosphoric acid solution is proven to not affect the aluminum surfaces or cause further pitting.
  • Deoxidizing: To strip the aluminum surface, you can also use a strong de-oxidizer. The aluminum anodized coating is actually a thick oxide layer, and to de-anodize would mean to get rid of this top layer of finishing. Here’s one way to remove the anodic finish from a knife. It also serves as a good guide on how to remove anodized color from aluminum. — Old Lumens uses this method

Looks really good MoreHiCRILumens! That scratch on the head would’ve bugged me too.

So is it now gray, or is it somewhat shiny?

You can also only de-anodize certain areas such as just a ring or just the knurling or just the head. You can even de-anodize your name or a logo using stick on vinyl,
I use a vinyl cutting machine and inkscape to create designs, although it takes me awhile to figure it out. Once its cut you just stick it on the part your removing anodizing from pressing it down real good and dip a cotton ball or cotton rag in the caustic soda solution. keep the area your de-anodizing wet until its de-anodized then rinse off. Pull the vinyl off and your done. It helps to have a stronger solution when just wetting versus dipping and dont forget to wear gloves. :wink:

Whenever I use Lye I keep some vinegar around to put on my skin in case of contact. It neutralizes the caustic soda very quickly, and if used fast enough it can definitely stop or seriously reduce a burn.

Wow, that’s much shinier than what I thought it was! Looks very close to the original Convoy clear (silver) S2+:

The silver (clear) S2+ has a coating on it to keep it shiny. I see that the silver is only available with a metal switch now, the silicone switch version seems to be sold out. Glad I got mine when I did.

That is a superb collection of lit silicone switch S2s.

I’ve just ‘discovered’ Convoys and I love the lit switch (have blue in an orange S21 B35AM and an orange light in a 12 mode S219b sw35 non biscotti Cyan S2+ Behind the metal switch, which works but isn’t amazing).

I’ve been trying to find the silicone switch on anything other than the grey or black and am disappointed if the clear/silver no longer comes with it.

If anyone can point me in the direction of a colored S2+ with silicone switch, I’d appreciate it. (Or anyone in Europe prepared to sell me one?)