Blackening Aluminum

One of the Simple Green formulas is supposed to darken aluminum. Some of the pics I've seen look black. Not sure how long it lasts though.
 
The purple degreasers will darken aluminum also if used full strength & left on too long. Found this out by accident. It says on the bottle not to use on aluminum but hey, who reads labels? :D

Still not a deep black, just a very dark gray like the alumnum blackener & its not very durable.
 
Buffalo21 said:
Wide tip Sharpie??....................
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I use black and blue Sharpies on parts I'm milling to keep tabs on dimensions, hole location, etc. Works great for that purpose, but usually after handling a few times, there's more on my hands than on the part. For this application, it needs to be more permanent than that.
 
Probably more involved than you want to get but nothing is as bulletproof as powder coat.
 
C-Bag said:
Probably more involved than you want to get but nothing is as bulletproof as powder coat.
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Yep. Best way for sure, but a little over the top for this application. Paint is sounding better and better.
 
Just read a well-written article in "The Home Shop Machinist" (Jan/Feb 2021 issue) about anodizing aluminum without using a sulfuric acid solution. The process described uses sodium bisulfate (NaHSO4) available at pool supply stores. Various colors were achieved using RIT dye from the grocery store. He did not dye anything black, but the colors looked good. He used a 1 ampere battery charger for small parts and a 4 ampere charger for larger parts. With some experience with power supplies, various regulated DC supplies would work. And no, I have not done any aluminum anodizing. Just passing the info along.
 
As mentioned before there are 3 types of anodizing and 2 classes commonly. What's happening is the outer layer (we're talking .0001-.003) is being converted to an aluminum oxide crystalline structure. Most home anodizing solutions are decorative and provide good elemental resistance without surface distortion. Hard anodizing is a little more involved and require a means to control the solution temperature and a few other variables; it usually has a color phase from dull grey (thinnest layer) to gold to brown to black (thickest) and a somewhat flat or rough finish.

For your application powder coat is probably the more user friendly surface finish and with the introduction of polymer suspended ceramaics provide a durable hard finish with minimal dimensional change.
 
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Alter Machine said:
As mentioned before there are 3 types of anodizing and 2 classes commonly. What's happening is the outer layer (we're talking .0001-.003) is being converted to an aluminum oxide crystalline structure. Most home anodizing solutions are decorative and provide good elemental resistance without surface distortion. Hard anodizing is a little more involved and require a means to control the solution temperature and a few other variables; it usually has a color phase from dull grey (thinnest layer) to gold to brown to black (thickest) and a somewhat flat or rough finish.

For your application powder coat is probably the more user friendly surface finish and with the introduction of polymer suspended ceramaics provide a durable hard finish with minimal dimensional change.
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I tend to agree the optimal choice is powder coating. Now it comes down to the issue of sufficiency: Is powder coating overkill? Or, conversely, is paint inadequate? I have a headache.
 
tjb said:
I tend to agree the optimal choice is powder coating. Now it comes down to the issue of sufficiency: Is powder coating overkill? Or, conversely, is paint inadequate? I have a headache.
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All these processes are not as simple as getting out the rattle can. I on average powder coat between 21 to 60 pieces a week so it works out for me, but it is a PIA because there are factors like the weather, humidity and wind that complicate whether I will even be able to do a run. But there’s no way I’d go through it for just one part.
 
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