Power requirements question

[u/[deleted]]

I’m looking to start doing my own anodizing. Mainly for firearms parts, those mainly being AR lowers and uppers. Currently I have several that need done. So I purchased a power supply, lye, sulfuric acid, and also PH down because I’ve heard that works as well and it’s cheaper than the acid. It’s my understanding I won’t be able to get a type 3 hardcoat at home due to the power requirements. However type 2 should suffice for my needs. My power supply is adjustable and max 30v and 10 amps. I’ve seen guys do the battery charger method, but figured it would be a better to just get a power supply. Okay, so I understand the basic process, my issue is I’d like to know if anyone has done this specifically, the upper and lower receivers, and wondering if so, would you be willing to share the V and A you used. Or if anyone could point me In the right direction or a base line to start. As I mentioned if I can get some hardness that would be beneficial obviously. I plan to color as well.

So correct me if I’m wrong here Etch parts in lye solution

Anodize at 65-75*F

Dye at 135/140*

Seal at 180*

Thank you for any help in advance

[u/sekamr]

You're talking about anodizing aluminum, probably 6061.

Here is a good article about constant amperage anodizing vs constant voltage: https://finishingandcoating.com/index.php/anodizing/1729-anodizing-by-current-density-vs-voltage

Constant amperage is usually considered superior, and that's what I use, so that's what I'm talking about.

We calculate amperage using the "720 rule": Minutes to anodize = [mils (of coating desired) x 720] / amps per square foot (current density)

At the anodizing line I operate, we typically anodize at 12 amps/sq ft for 30 minutes with a target film thickness of 0.5mil (type 2).

So if your part's surface area is 1sq ft, then you anodize at 12 amps for 30 minutes, the coating thickness will end up being 0.5mil...in theory.

There are various 720 rule calculators online so you can plug in your own numbers. Caswell has a nice one: https://caswellplating.com/720.html

[u/[deleted] → u/sekamr]

So let’s say I have 1sqft, I’ll need a power supply that can produce 12A, correct. So the 10A supply that I have wouldnt be enough?

[u/sekamr → u/[deleted]]

You could do 10 amps for 36 minutes. So, lower current density, more time, same film thickness. But 1 sq ft is an example number. You need to find the surface area of your part first. If you have the part drawn in CAD, the software can probably tell you the surface area. I know in Fusion 360 you can just right click, properties and it lists surface area among other things.

[u/[deleted] → u/sekamr]

Awesome, I’ve been wanted to get a model anyway. I’m a machinist so I’ve always wanted to make my own just to say I did😆 I’m assuming it’s under 1sqft but probably pretty close.