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  #1  
Old 05-30-2007, 06:09 PM
SPRINGFIELD SPRINGFIELD is offline
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Black Patina for Aluminum

Iv'e made some aluminum castings and now I would like to use some chemical to turn the aluminum black. What I would like to do is turn the aluminum castings black and than polish the high spots. Kind of looking for the effect that they get with silver jewelry.
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  #2  
Old 05-30-2007, 07:44 PM
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fritchie fritchie is offline
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Re: Black Patina for Aluminum

I think what you will have to do is oxidize (anodize) the aluminum in a solution that contains some black or very dark, permanent dye, and then polish away the areas you want. No aluminum compound is dark in color, unlike copper, iron, or other metals. I'm sure there is much discussion of anodizing aluminum on the Internet, but I can't give specific references. I think this is quite common in jewelry, though, for example.
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Old 05-30-2007, 09:18 PM
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allenring allenring is offline
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anodizing is the answer

Aluminum is the only metal that can be dyed. That means that the grain structure of the metal will absorb a dye to a depth of about three thousands of an inch. This ability is what makes anodizing, clear, black, blue, etc so effective. When you want to polish to bare metal, get ready to remove some metal.

You can purchase cold anodizing pens and dyes fairly cheaply but they are not very effective. To get a good black finish like a piece of stereo equipment you need to go through the anodizing process. That involves dipping the metal in sulfuric acid to open up the pores and remove the oxide. Then the metal is dipped in the dye solution with a current running through it. The electric current is what caused the metal to absorb the dye.

This is not something that could be done at home to say the least. Check your area, their should be plenty of metal platers, companies that rechrome bumpers, replete silver pieces and anodize aluminum. The only problem you may have is the fact that this stuff is so environmentally nasty that California may have chased them out of your area. My plater had to move south to the boonies to stay in business.

Your a machinist so you know that aluminum will oxidize once you remove the protective finish. I have bead blasted aluminum, real sexy matte finish, but the material is so active that a thumb print instantly oxidizes it to a nasty gray color. I just spray it with lacquer to seal it, works great.
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  #4  
Old 05-30-2007, 09:26 PM
SPRINGFIELD SPRINGFIELD is offline
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Re: Black Patina for Aluminum

Quote:
Originally Posted by fritchie
No aluminum compound is dark in color, unlike copper, iron, or other metals. I'm sure there is much discussion of anodizing aluminum on the Internet, but I can't give specific references. I think this is quite common in jewelry, though, for example.
That's interesting and thanks. I guess therefore there is no chemical reaction between aluminum and anything that will produce a black surface. Therefore I will have to color the aluminum and not rely on some chemical reaction to get the black color. Since I plan to lacquer the finished aluminum someother way of coloring the aluminum would be ok. I just thought a patina might be more permanent.
Has anyone tried cooking on some Asphaltum and does anyone know where I can get some? I saw it talked about in a book.
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  #5  
Old 05-30-2007, 09:43 PM
SPRINGFIELD SPRINGFIELD is offline
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Re: Black Patina for Aluminum

Thanks allenring
The castings come out of the mold with a little black on them which I buff off with a fine wire brush. It leaves a nice silvery finish but I'm sure it would look better with a slightly darker black color in the details. So my plan is to get something to color the aluminum black. buff off the extra black, and than as you suggest right away laquer it. I was wondering is there any kind of laquer that you might suggest, I plan on having some of them outdoors. Thanks again for all the information.
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  #6  
Old 05-30-2007, 10:12 PM
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Re: Black Patina for Aluminum

Just got tougher. Their is no form of lacquer that will hold up in an exterior environment. Virtually any type of aluminum for exterior use is clear anodized. You need to switch to a clear coat automotive finish. You could start with a black automotive paint for the highlights and then clear coat it. Your problem will be that the metal needs to be primed first so that the car paint will stick. That puts you back to getting the piece clear anodized before you paint it.

Or try this, use spray cans of Rustolium, great stuff and made to go over bare or rusted metal. I think they also have a clear coat but I'm not sure.
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  #7  
Old 05-30-2007, 10:36 PM
Harryman Harryman is offline
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Re: Black Patina for Aluminum

If you want a black that will imitate a patina, use Sprayon #204 spray graphite. You'll find it at industrial supply houses. Spray on and scuff off with Scotchbrite or steel wool etc. That'll leave you black in the recessed areas with nice gradation to bright unlike paint which is all on or all off. It works great on any metal by the way and is solvent based so besides killing brain cells, it dries in about 15 seconds.

You might try wax for a finish but it'll try to take some of the graphite with it.

Any clear coat won't weather well.

Bare aluminum will oxidize/anodize to a light grey if exposed to the elements. Same color as anodized aluminum without dye. You can anodize AL yourself with a battery charger and sulfuric if you're feeling brave, it's pretty easy.
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  #8  
Old 05-30-2007, 11:16 PM
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Ries Ries is offline
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Re: Black Patina for Aluminum

If you are in Burbank, you are just a few miles from probably the biggest, and best, anodizer in the world.

George Industries- they have invented more processes to do with anodizing than almost anyone. They do all the maglite flashlights, and invented camoflage anodizing, Marbles, Fades, and all kinds of other stuff nobody can do.

Of course, they arent cheap. But they could certainly anodize your aluminum black, with a clear coat over it. And that would stay that color, outside.

http://www.valmont.com/asp/coatings/.../finishes1.asp

There are still a few other anodizers around LA- not ALL the aerospace industry is gone.
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  #9  
Old 05-30-2007, 11:31 PM
SPRINGFIELD SPRINGFIELD is offline
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Re: Black Patina for Aluminum

Thanks alenring.fritchie and Harryman I sure am glad I posted this question. You guys sure gave me a lot of good advice and things to think about. Right now I'm thinking the grafhite spray and than rustolium clear.
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  #10  
Old 05-31-2007, 09:11 AM
Harryman Harryman is offline
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Re: Black Patina for Aluminum

Just make sure you use "Sprayon" brand, others don't work as well.
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  #11  
Old 05-31-2007, 01:58 PM
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Lunarburn Lunarburn is offline
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Re: Black Patina for Aluminum

https://www.birchwoodcasey.com/store/antiquing.html#oxd

ALUMA BLACKŪ A14 BRUSH-ON
A handy brush-on blackener for all aluminum alloys. Use undiluted to blacken entire parts or as a touch-up for black anodizing that has been re-machined or damaged. Ideal for engravings.
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  #12  
Old 05-31-2007, 03:34 PM
SPRINGFIELD SPRINGFIELD is offline
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Re: Black Patina for Aluminum

Quote:
Originally Posted by Lunarburn
https://www.birchwoodcasey.com/store/antiquing.html#oxd

ALUMA BLACKŪ A14 BRUSH-ON
A handy brush-on blackener for all aluminum alloys. Use undiluted to blacken entire parts or as a touch-up for black anodizing that has been re-machined or damaged. Ideal for engravings.
Thanks Lunarburn, that is just the thing I'm looking for. I especially like the part about ideal for engravings. Perfect.
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  #13  
Old 06-01-2007, 10:51 AM
SPRINGFIELD SPRINGFIELD is offline
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Re: Black Patina for Aluminum

I just found a exterior laquer designed for metal sculpture.
www.permalac.com
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  #14  
Old 06-01-2007, 12:56 PM
Arrow Arrow is offline
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Re: Black Patina for Aluminum

http://cgi.ebay.com/Aluminum-Anodizi...QQcmdZViewItem


I can not attest to the quality of this kit. But the process is pretty simple...That is if you can cautious handle sulfuric acid.
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  #15  
Old 06-01-2007, 01:19 PM
anatomist1 anatomist1 is offline
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Re: Black Patina for Aluminum

They say that permalac lasts 10 years outside. Sounds doubtful to me, but there is no doubt it is way tougher than normal lacquer. I had to blast some off of a steel base to correct a mistake. It had only been drying on there for about 40 minutes and it took forever to get off - maybe 5 to 10 times more blasting than removing fire scale or normal lacquer. It's also less drippy and more resistant to blemishes when you apply it. It has a sort of yellowish hue, as opposed to regular lacquer, which seems blueish.

For indoors, the simplest thing that sounds like it might do what you want is dyed wax. You apply it with mild heat, then buff as you want. Heavy buffing will push the black into the crevices, then you could add a clear layer and buff lightly. It's a nice finish that is much less plasticky and more organic-looking than clear coats. Sculptnouveau sells a black wax, as well as permalac.
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  #16  
Old 06-01-2007, 07:18 PM
SPRINGFIELD SPRINGFIELD is offline
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Re: Black Patina for Aluminum

Thanks Arrow and anatomist you guys have given me a lot to check into. Today out of desperation I got some Henerys roofing compound , thined it out with some mineral spirits and thru in a little black concrete color. I tried it without the concrete color but it had sort of a brown hue to it. Anyway it looks pritty decent. Tomorrow I'm going to try some linseed oil and black cement color. Don't know if the laquer will stick to it though when I'm done.

I'm hoping to sell some of my small castings and cost of materials is a big factor. Kind of like the wax idea I'll have to try it.

Last edited by SPRINGFIELD : 06-01-2007 at 07:21 PM. Reason: more words
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  #17  
Old 06-01-2007, 08:14 PM
anatomist1 anatomist1 is offline
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Re: Black Patina for Aluminum

I've only done one piece with linseed oil, but it can make a nice light to dark brown finish. The method I used was to apply it in tandem with a propane torch. Heating it to around its melting point will produce a light brown tint. Burning it will produce dark brown, but also vaporize most of it. If you keep applying and keep burning, you could eventually get a piece that is solid dark brown. I did some burned and some melted for an indoor piece and put nothing over it. It looked pretty good, but it stayed sticky for a long time.

You might be able to dye wax yourself. The fancy stuff you buy from a patina place is basically the same as floor wax in paste form. You might want to go to a hardware store and buy a tin of Johnson's or Triwax and scoop out some chunks and melt them and mix dye in, then keep some clear for a final coat. That plus a hairdryer and some chip brushes and you'll have an extremely cheap, easy, low-toxicity finish for indoor pieces. I would put wax on everything myself, except some of my pieces have too many small, delicate details and are essentially unbuffable.
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  #18  
Old 06-10-2007, 08:23 AM
PTsideshow PTsideshow is offline
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Re: Black Patina for Aluminum

He a link for home anodizing
Here is the site for all questions on coloring metal
They have a section for the artist/hobbyist and for production shops. It takes a day or two to get a response after registering.
The archives of questions asked and answered is mind boggling.
And a side note if you have seen the new colored sockets that Harbor fright is selling they are transparent colored lacquered with a clear coat also the dark colored sockets are the same.
This is the same as on the open and box wrenches they are selling. Enclosed are a couple of pictures of abusing the said sockets to settle the question on another site that you can anodize metals other than aluminum! You can not anodize anything other than aluminum.
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Old 06-10-2007, 01:32 PM
Arrow Arrow is offline
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Re: Black Patina for Aluminum

Titanium can be anodized.

http://www.popsci.com/popsci/how20/3...cbccdrcrd.html

"With a battery and a can of soda, you can anodize the surface of titanium to create colors that will last forever"
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Old 06-10-2007, 03:47 PM
PTsideshow PTsideshow is offline
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Re: Black Patina for Aluminum

that isn't anodizing in the strict usage of the terms used in the industry. It is colored with an electro plating process. As with most things now the terms are used fast and lose. The sockets are lacquered, from removing the so called anodizing with a solvent and it was on steel.
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Old 06-10-2007, 09:49 PM
cooljamesx1 cooljamesx1 is offline
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Re: Black Patina for Aluminum

Quote:
Originally Posted by allenring
Your problem will be that the metal needs to be primed first so that the car paint will stick. That puts you back to getting the piece clear anodized before you paint it.
no need to anodize before painting. just get yourself a can of serwin-williams self-etching primer. it etches it's self into the aluminum, stuff is awesome. used it to paint my boat.
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