Oxidizing Aluminum

[Brian Robison]

Any one ever do this?
I have a bottle of Aluminox from JDS but I have no instructions. I looked at the world wide web until I reached the end of it with no luck.
HELP!!!!!:(

[Dave Jones]

I've never done it. All I know is what I've read. That it is applied to freshly cut mechanical engraving to darken the raw metal.

[Brian Robison]

Thanks Dave,
Just hoping it will work with the laser too. Looks like as long as it's exposed aluminum it would work but I see no reference to laser engraving, only mechanical.

[Dave Fifield]

As far as I can tell, oxidized aluminum is more commonly known as anodized aluminum. In its pure form, it's kind of white-ish/grey-ish boring looking surface. Normally it's then dyed to whatever color you want, then it looks great.

You can laser engrave the surface of anodized aluminum. The CO2 laser does two things. One, it burns out the dye in the aluminum oxide layer, and two, it takes off a couple of thousandths of an inch of the anodized layer. If the anodizing isn't very thick, you can actually remove it completely down to the bare shiny metal. Thus, the finished look is either kind of white-ish/grey-ish, or shiny aluminum (which looks fantastic!).

HTH,

[Jeanette Brewer]

Thanks Dave,
Just hoping it will work with the laser too.

Brian,

One of the beauties of the laser mark on metal is that it will not oxidize over time. The flip side of that is that you can't oxidize it the way you can mechanical engraving.

I'll have to leave the "why does it work that way?" to the chemistry experts. I just know that's the way it is.

[Brian Robison]

Well, that's not what I wanted to hear!:eek:

[Dave Jones]

Yeah, my understanding is that material is not for use with a laser. If you want a black mark on clear aluminum, use CerMark. If you want a grayish white mark on black or colored anodized aluminum you need nothing but the laser.

[Brian Robison]

It's not anodized and I'd need more power than 25 watts to do Aluminum. Had I known that when I bought it I would have gotten a more powerful laser.

[Eric Allen]

Brian, can you sacrifice a part to testing? I have a possible solution, but I haven't done it on Al. Ah yes, and how big is the part?

[Brian Robison]

The part is small, 4 inches long 1/2" diameter.
I'm hoping to fix the parts I've used for testing so
far by touching up the paint. Paint looks bad anyhow.
It a military part so it's that olive drab flat paint.

[Eric Allen]

Wish I had some extra AL laying around to play with, I'd like to try this process on it. There is an etching process, and you can use different compounds to pull it off, in steel for certain but AL I don't know the end result. The worst possible outcome is the removal of the paint, so if you want to take the chance: Try mixing up a small bowl of hot water with salt. Using salt you should do this outside, there is a small chlorine risk, though you'd probably get more standing by a swimming pool. You can use sodium carb, or bicarbonate, but I don't remember which, the salt I know works. Mix in as much salt as the water will take in. Take either a 9volt battery or charger/power supply and hook up the positive to the item to etch, the negative to a small piece of copper (like 12gauge wire) and set it near, but not touching the piece, and hook up the negative. If you use an adapter, sometimes it's good to put a load in line like a little computer fan or something to keep the load regulated. Anyway, this process will etch steel, stainless, and I think brass, so it could be worth a shot. If the leads are on backwards it's more likely to remove the paint if I remember right.
It's a cheap, easy test, and if it works, it should alter the area that you used the laser to remove the paint from. This only takes around 5 minutes or so on steel and you can remove the parts and put them back in with no ill effects. Oh, just so I'm clear, that power supply MUST be DC output. And best of all, no indexing:D

[Mike Null]

Brian

To oxidize aluminum you must remove the surface to get to the raw aluminum. Regardless of the power of your laser it will not do the job.

I have used a mask and sandblasted both aluminum and brass then oxidized. You can also used something as simple as a pantograph to mark the numbers or you can make a stencil and paint on the numbers.

[Stephen Beckham]

Can I request that you video your attempt if you try Eric's suggestion.

I like the sound of it and bet it would make a great video...

Either instructional or for submitting to the Darwin Awards :D

[Brian Robison]

Thanks for the input. I did a test last night on the oxidizing. Scratched with a chisel the aluminum oxidized, lasered it didn't. If it was a few parts I'd try something but it's 3500 parts. :(

[Mike Null]

Brian

What about finding somebody with a pad printer. They would probably do it for $.10 each or less.

[Brian Robison]

I think they wanted something engraved into the paint.
It's not been an easy job, I've had to go back to the customer too many times. I tried masking and painting last night with out success.

[Eric Allen]

Can I request that you video your attempt if you try Eric's suggestion.

I like the sound of it and bet it would make a great video...

Either instructional or for submitting to the Darwin Awards :D

I'll make you a copy if I ever get around to trying Al. No danger of it making the Darwin Awards unless someone tries to use some insane amount of current or straight A/C (useless for the process, gotta be one way), but then, those books DO exist for a reason:D I really feel compelled to try Al now, just to see if it would make a difference in the surface. It does amazing things with other metals. The nice thing is, if you ramp up the current and add more prods, you can batch process a bunch, so it would be perfect for an application like this if it aluminum will add oxide through the process. I'm not sure, since Al by it's very nature forms a protective oxide within minutes of being exposed. Neat stuff:) Oh, if you hook the terminals up backwards from what I said and make a piece of rusty steel your primary target, you will be AMAZED at how well it removes rust. I found where someone used Arm & Hammer Super Washing Soda (not baking soda), I think that's the right chemical I was thinking of instead of salt, same instructions otherwise, except probably better to use iron bar/square stock in that process instead of copper. It's better than salt as an electrolyte in a couple of ways, and not as dangerous as other electrolytes. I have a little love affair with electrolysis, if you hadn't noticed:)

[Brian Robison]

I've used the process to clean parts. Kinda worked but it damaged my 12v trickle charger.

[Eric Allen]

Yeah, that's where the load comes in. Batteries you don't usually have much issue with, but any kind of charger is going to be stressed without a load in line. The process will take what it can. If you put an 80% load in line with the circuit, ideally the draw will be limited to that load. I'm going to use a 2A/6v source for my Al test, might squeeze it in tonight if I can find some scrap around to paint and test. Ideally with one cathode and one anode it would be 2.4-3V. I suddenly really want to know this answer for myself as well:) I'll paint completely, laser it away, then get sparky and see what happens. What font and what size numbers? I'll try and make it as true to life as possible, and I promise not to win the Darwin Award so you get to see the outcome before the next book:D

[Eric Allen]

Here's something that may help. I had to paint this Al to do the test. I used black Rust-Oleum satin paint, and even running overpower, it didn't completely penetrate to the Al in most spaces. On my machine, 100s, 30p, and 600 dpi would probably have made an almost perfect white contrast without cutting all the way through the paint. Maybe if you use that particular paint over the items first, then lase? Might just do the trick.

[Brian Robison]

Update,
I looked at my sample part this morning and the lasering turned black. It just took several days to oxidize. Interesting.

[Eric Allen]

That's interesting. Seems like the oxides are usually a kind of white/gray. That's what I think is under my paint, pretty sure it must have created something like a thin anodized layer, mine is white. I can see the surface imperfections under the layer, but it's more heavily capped than just normally exposed Al. We need a chemist for the board:)

[Richard Rumancik]

. . . I did a test last night on the oxidizing. Scratched with a chisel the aluminum oxidized, lasered it didn't. . . .

You have non-anodized aluminum under paint. After lasering, the oxidant would not touch the exposed zones but you said that after a few days it turned black. Correct? So the reaction seemed to be very slow. If you could speed up the reaction maybe it would be viable? Maybe increase the temperature a bit? Of course, it would have to be such that the paint itself was not damaged. An increase in temperature will normally increase the rate of a chemical reaction, but I don't know if it will still be fast enough to be practicable.

Can you test for conductivity of the lasered area with an ohmmeter? I'm curious if the exposed area is a conductor or insulator. Anodize is an insulator. If the laser-exposed surface is conductive, there is a greater chance of being able to affect it chemically or electrolytically. (You need to just lightly touch two exposed characters with the probes and see what you get. Try in a few places.)