Removing the anodized layer on aluminum..??

[Randy Digby]

I currently drag diamond engrave gold, yellow and silver anodized plates and then apply aluminum oxide to blacken the text for readability. I understand that when lasering anodized aluminum that you are really bleaching the anodized layer out and the aluminum is not exposed. Is it possible to take the anodized layer completely off and how much power would you think that would take (probably more than my 30W)? If it is possible to completely remove the anodized layer, would the exposed aluminum react with the oxide solution and oxidize black as in scratch engraving? Anyone been there - done that?

[Rodne Gold]

You wont get to bare metal with the lasers , there is always a residue left and albeit you will get reaction to the oxidiser , it will be "patchy" or inconsistent

[Dave Johnson29]

If it is possible to completely remove the anodized layer


You can try Lye (Sodium Hydroxide) but be VERY careful mixing it. It will eat flesh and destroy eyes in a heartbeat. Read mixing instructions carefully as it is VERY important how you add which to what.

Use about a 10% solution in water. What you will finish up with is bare aluminum that will react just like, well, er, bare aluminum. :)

[Brian Robison]

You can mask with a laser mask and then sand blast before oxidizing. Takes a little longer but not too bad.
Works with brass too.

[Randy Digby]

Thanks for the feedback. You all answered my basic question..it ain't going to happen with a laser and normal raster engraving.
Thanks gang,

[Michael Hunter]

I do quite a lot of aluminium and have several different settings as some needs very small text (~1mm high) whilst other bits get big bold engravings.
On one occasion I accidentally used the high power "fine detail" setting for a bold piece and it ***appeared*** to take off all the anodised film completely, leaving shiny bare metal. I say "appeared" as the piece was then scrap and I did not pursue it further.

So it might be worth trying on a scrap plate (my settings were 25% power, 75% speed on a 60W laser).

No doubt Rodne will be proved right and when you WANT to remove the layer it won't come off cleanly, but still worth a go.

[Randy Digby]

Good info Mike. Can't wait to get the machine. Had a few delays in it's arrival but should have it up and running in a few days. I have to get dark lettering on gold and yellow anodized and don't want the hassle of Cermark (sp) because of the quantity I have to deal with. I'm trying to use info from this forum to decrease my learning curve. Lots of good stuff here.
Thanks,

[Brian Robison]

When you say quantities, do you mean a lot or just a couple?

[Randy Digby]

They are 1" x 3" x 1/16" plates with one to three lines of text and we may do from 1 to 100 in an order, each with different text.

[Mike Null]

Regardless of how much power or how many times you burn it the laser will not get you uniformly to bare metal.

I agree that it looks like bare metal but there is still a coating there.

I have used the laser/sandblasting combination and it is reliable but takes time.

[James Rambo]

Why not try gold Alumamark sheet?
Does it have to be 1/16 " Alumamark from Johnson Plastics is only 0.020".

[Randy Digby]

Has to be 1/16". I think I've got a solution that will work. Being able to oxidize the aluminum would have been my first choice, but I think I can darken the text sufficiently in a couple of other ways.

[Rodne Gold]

Well there is a nother solution , mask the plate with masking tape or paper based application tape , laser so that you remove the tape and leach the colour and then spray with black car paint or high heat engine block paint. The paint will / should penetrate the porous anodising and be as permanent a mark as your oxidised scratch engraving. Not sure whether seepage under the tape mask would be a problem but if you dont douse the thing in paint , it shouldnt be.

[Bill Cunningham]

For plates, I use black enameled Aluminum. It lasers to bright silver on black..
You can also get Enameled Aluminum in many other colours as well.. If you 'need' black on silver, you can invert it, and 'leave' the black text.. But I also find Alumamark both gold and silver work quite well.. Your lasered plates will look quite different than the diamond scratch ones anyway, no point in trying to duplicate the old way.. Clear coated aluminum can be lasered, and oxidized if thats the way you really have to go..