Making aluminum different colors

I'm screwing around with some electronics, and I want to do something interesting with the aluminum enclosure. Specifically, I want it purple and I'd like to engrave through it down to the base metal. The engraving is not a problem, I have a hookup there.

First choice would be purple anodizing, but the local anodizing shop doesn't do purple as a normal color so I can't piggyback on a larger job and they're talking about a $100 minimum charge. Has anyone tried any DIY anodizing?

Powdercoating is a distant second choice, but I don't have any tools for that either. I can tell you that if I used the kitchen oven for powdercoating you would never hear from me again - Margie has her patios, but my wife works in heavy highway construction.

Paint is possible, but just kinda blah...unless I learn to shoot metallic. Hmm.

Any thoughts from the hive?

I have a complete kit I got just before the telescope guy (Ron Newman) stopped selling kits.  Sadly his Yahoo list went to hell too.  I belive there's purple in the kit let me see if i can dig up the cost and i'd sell it for what i got in it.

http://www.uponone.com/howtos/1.pdf

I googled this a bit and I learned something today! I had no clue that anodizing just built up a shell of harder oxidation than aluminum usually forms around the aluminum and you dyed that layer whatever color you preferred. Interesting.

I know, I didn't expect that either. But apparently you can't just skip the anodizing step and go straight to the dye.

Correct. the oxide layer is porous and for the color to last it real needs the fixer step to close up the pores some people cheap out and just boil parts but the color will fade....like bell bottom jeans.

Looks like it's something you can do with an isolation transformer and some chemicals. Should be cakewalk for you.

In reply to Keith Tanner :

Caswell offers anodizing kits and dyes, and purple is most definitely an option. If you have the power supply (or can borrow one) the bottle of dye is 15 bucks for 2oz which will make 2 gallons of fluid. Then all you need is a bucket, sulfuric acid, distilled water and a cathode. I bet you could do it for less than 100 bucks.

A friend of mine has done a receiver in purple and anodizes on a semi regular basis. Supposedly all you need to do is use a hydrometer to make sure the solution is still viable as it keeps for a long time when you put an airtight lid on it. Came out really nice.

My understanding is that some colors are normal, others are hard, and others are impossible. I think purple is normal. I'd try a different guy if the DIY stuff is not working out.

I did this in high school without any electrolysis, aluminum will naturally anodize in air (only a thin layer). so what you do is strip the aluminum part with oven cleaner, then have a pot of your chosen dye mixed up with warm water. leave the part in there for 15 minutes then bring it to a rolling boil for 30 minutes. this will produce a dull and thin anodize finish. darker colors work better and PS dont use a pot you use to cook in lol.

tuna55 said:

My understanding is that some colors are normal, others are hard, and others are impossible. I think purple is normal. I'd try a different guy if the DIY stuff is not working out.

Different guy is unfortunately not an option because there's only one in town. Purple is fairly normal, but not a color they regularly offer. Red, black, blue IIRC. We have parts that are anodized purple but IIRC the anodizers are in Wisconsin where the machine shop is so I can't piggyback on an order.

I do have access to a fairly burly DC power supply (Mastech HY3030E, good for 30A of zappy fun) so the DIY anodize is a possibility. I was hoping someone here has tried it and can give feedback on how well it worked.

44dwarf, thanks for the link. Looks like one of the better writeups I've seen.

In reply to Keith Tanner :

You may want to try any gunsmiths in your area. Alot of times they can run a small batch. It's popular for Aluminum gun parts.

echoechoecho said:

I did this in high school without any electrolysis, aluminum will naturally anodize in air (only a thin layer). so what you do is strip the aluminum part with oven cleaner, then have a pot of your chosen dye mixed up with warm water. leave the part in there for 15 minutes then bring it to a rolling boil for 30 minutes. this will produce a dull and thin anodize finish. darker colors work better and PS dont use a pot you use to cook in lol.

I did this with some RC car parts years ago.  I think I used Rit clothes dye and ruined one of mom’s good pots.

Well if you can dye aluminum without a power supply, I'd have to guess you could get away with less than 30 amp 12vdc.

Papabear said:

In reply to Keith Tanner :

You may want to try any gunsmiths in your area. Alot of times they can run a small batch. It's popular for Aluminum gun parts.

Purple? One of our suppliers does gun stuff primarily, but all his stuff is tacticool matte black. It's a good idea, though, I'll sniff around.

In reply to Keith Tanner :

May be you have to get the dye. But here locally I've seen some crazy color combos. Red's and Blue's, Gold and Silver. Gunsmiths also alot of time do Cerakote that you can get in Purple also. And normally they run much smaller batch's than a powder coater.

I know our local powdercoat place does Cerakote. I'm not sure it would be much different than paint, aesthetically - although probably easier for engraving through it.

This is good stuff.

Not a practical option, but an interesting and very relevant curiosity: Did you ever notice that the mufflers on Pagani cars are purple? Probably anodized, right? No, they're heat-treated(!) a perfectly uniform purple with a mask applied in the shape of their logo.

I have some friends who are into knifemaking as a hobby. They work a lot with titanium, which will change colors along a spectrum from yellow to blue if you heat it to specific temperatures. I've seen them get some nice shades of purple that way. Would that work for aluminum as well?

That would be cool, but unfortunately that's titanium oxide IIRC. Only a few metals do that trick.

So, blue and red are more common dyes for anodizing than purple. Last I knew, red and blue mixed together make purple.

If I worked at an anodizing shop, that would probably be a legit option. But when you're running a business, doing a special run of dye for one small part is a PITA and gets charged accordingly.

Just ship it to me, I'll powdercoat it for you. You buy the powder, $15 or so.

So what did you do?

Go for it Keith!  I was able to figure out anodizing in high school (ca. 1998) with a book I got from the library.  a 12v battery charger, pool acid, and RIT dye were the most important components.  

tuna55 said:

So what did you do?

I went on vacation.