Blackening Aluminum

[tjb]

Anybody have experience blackening aluminum? I'm working on a project that will have a part that needs to be black (or close to it). The part will be made out of 6061T6 aluminum; it will be about 2-1/2" long, 3/8" diameter round stock, knurled on one end, bored and tapped on the other. I could paint it, but it will be handled fairly regularly, so I'm wondering if blackening would be better.

I've never tried to blacken aluminum, but I know there is a product made for that purpose. Does it darken enough to be considered 'black'? Does it hold up well, or is fading an issue? Anything else I need to consider?

Thanks for any advice.

Regards,
Terry

 

[Flyinfool]

Anodizing is the most comon prosess to color aluminum. It is a durable finish. the color fastness is solely dependent on the dye that you use, some dyes fade really bad others seem to hold up pretty well. A quality paint will hold its color better than most color anodizing.

 

[tjb]

Anodizing is the most comon prosess to color aluminum. It is a durable finish. the color fastness is solely dependent on the dye that you use, some dyes fade really bad others seem to hold up pretty well. A quality paint will hold its color better than most color anodizing.

Thanks. Had not thought about anodizing, and I've never done it before. I'll study that. Any recommendations for products to use or others to avoid?

Regards

 

[graham-xrf]

There are complete how-to's on YouTube.
Essentially you use diluted battery acid, although in theory, any electrolyte capable of working against aluminium can work.
You can practice using beer can ring pull tabs. Small DC wall-wart power supplies can be convenient, but if you have a electronics hobbyist power supply with current control, is better.

Aluminium is so extremely reactive that when fresh cut, it forms an oxide in fractions of a second. This layer is so thin it is completely transparent. Even quite thick layers remain transparent, until they crack up into white powder.. With both electrodes made of aluminium, connect the power will build up oxide on one side, and cut through the oxide and wear away the aluminuim on the other. You end up making a sulfate, and hydrogen I think).

Depending on the chemicals and currents used, you can make two classes of anodized coating. "Hard" anodizing, and "decorative" anodizing. The latter is quite tough anyway, and would be the type you dye. After the dye is on, there are processes to "seal" it.

There are just tons of YT videos on how to do this. Best advice - do not just go for the first one you see. Look at at least four. You will get an idea of the "better" ones quite quickly.

--> LINK

 

[tjb]

There are complete how-to's on YouTube.
Essentially you use diluted battery acid, although in theory, any electrolyte capable of working against aluminium can work.
You can practice using beer can ring pull tabs. Small DC wall-wart power supplies can be convenient, but if you have a electronics hobbyist power supply with current control, is better.

Aluminium is so extremely reactive that when fresh cut, it forms an oxide in fractions of a second. This layer is so thin it is completely transparent. Even quite thick layers remain transparent, until they crack up into white powder.. With both electrodes made of aluminium, connect the power will build up oxide on one side, and cut through the oxide and wear away the aluminuim on the other. You end up making a sulfate, and hydrogen I think).

Depending on the chemicals and currents used, you can make two classes of anodized coating. "Hard" anodizing, and "decorative" anodizing. The latter is quite tough anyway, and would be the type you dye. After the dye is on, there are processes to "seal" it.

There are just tons of YT videos on how to do this. Best advice - do not just go for the first one you see. Look at at least four. You will get an idea of the "better" ones quite quickly.

--> LINK

Thanks for the advice. I just finished looking at two YT videos. I'll need to do more studying, but my knee-jerk is anodizing is going to be exactly the finish I need for this part.

Thanks for answering.

Regards

 

[Buffalo21]

Wide tip Sharpie??....................

 

[darkzero]

If you need it to be really black, anodize, cerakote, or paint.

For "blackening", there's a product by Birchwood Casey called Aluminum Black. Use it just as you would cold blue. But in my experience the stuff doesn't work that good, always gave me a dark gray instead of a deep black & it wears off easy. I don't recommend the stuff but you could give it a try, maybe you'll have better results than me? It's like $7 for a little 3 oz bottle.

As graham mentioned above about the different types of anodizing, standard "decorative" black anodizing will give you a glossy black. Black HAII & HAIII (hard anodized) will usually be a flat black. I'm not sure if anodizing types have evolved & are different these days.

I have no experience anodizing aluminum myself, only titanium, but when I was interested in DIY solutions it seem a bit dangerous & toxic to be doing in my home garage. Again, maybe things have changed these days? IIRC the hard anodizing can't easily been done at home. Also if you try to go to an anodizer, they'll have a minmum set up charge so it won't make sense cost wise if it's only a few parts or less.

Also check out https://caswellplating.com/ They have anodizing kits & may have their own aluminum blackening solution. Their products are great, never been disappointed in any of the stuff I have purchased from them.

 

[tjb]

If you need it to be really black, anodize, cerakote, or paint.

For "blackening", there's a product by Birchwood Casey called Aluminum Black. Use it just as you would cold blue. But in my experience the stuff doesn't work that good, always gave me a dark gray instead of a deep black & it wears off easy. I don't recommend the stuff but you could give it a try, maybe you'll have better results than me? It's like $7 for a little 3 oz bottle.

As graham mentioned above about the different types of anodizing, standard "decorative" black anodizing will give you a glossy black. Black HAII & HAIII (hard anodized) will usually be a flat black. I'm not sure if anodizing types have evolved & are different these days.

I have no experience anodizing aluminum myself, only titanium, but when I was interested in DIY solutions it seem a bit dangerous & toxic to be doing in my home garage. Again, maybe things have changed these days? IIRC the hard anodizing can't easily been done at home. Also if you try to go to an anodizer, they'll have a minmum set up charge so it won't make sense cost wise if it's only a few parts or less.

Also check out https://caswellplating.com/ They have anodizing kits & may have their own aluminum blackening solution. Their products are great, never been disappointed in any of the stuff I have purchased from them.

Thanks, Will.

I saw the Birchwood Casey product. It's actually the reason I made the original post. I've done a little bluing on steel with less than stellar results, so I'm not too confident I'll be satisfied with a similar product on aluminum. Flat black is the look I'm after on this part, so I'll look into the Black Hall & Hall.

This will not be a high-maintenance application. It will be a knob, so it will be handled some. I'm a little concerned that paint may decompose over time. Sounds like that may be an issue with Aluminum Black as well. And the potential for gray instead of black is a definite deal breaker. We'll see.

Regards

 

[darkzero]

I've had good results with cold bluing steels with Caswell's stuff & Brownell's. But that Aluminum Black I could never get anything better than a dark gray. The Aluminum Black actually works better on brass, haha (same company has a blackener for brass too).

Even if Caswell has an aluminum blackener still I doubt it would hold up well on something like a knob that will be handled often.

Not sure if you are part of any gun or knife forums. Sometimes there are guys that offer cerakote services. Another option is powder coat. But like anodizing, there may be a minimum set up charge if you go to a professional service.

 

[RJSakowski]

I tried the Birchwood Casey Aluminum Black and was not satisfied with the results. It may be OK to touch up small scratches but fails a a general blackening. Not much better than a sharpie and it rubs off.