Anodizing Aluminum at Home DIYS

[Hermit Scott]

Since everything on the internet is true, what I have read so far about anodizing at home must be pretty easy.
I have a tub inside a cooler, because anodizing works best around 65 to 70 degrees Fahrenheit, and the process causes heat. So I will put ice in the cooler and the tub sits in the ice.
The bar running in the middle that all the parts are hanging on is the anode and the positive battery charger cable hooks to that. Wikipedia says that's why it's called anodizing because the parts being anodized are the anode.
The two long plates along the sides are the cathode that the negative battery charger cable is hooked to. They say it's best to have as much surface area on your cathode as you do on the anode.
I have harvested 3 large sized mason jars of battery acid from two old batteries that came with my boat. I was concerned that it lost it's acidic properties because it sat so long, but I spilled some on my sandal wearing foot, it turns out it's still acidic.
All the metal that will be submersed in the electrolyte is 6061 aluminum. I have read you can use stainless for the anode, but it's way harder to cut to size so I went with aluminum.

I bought RIT clothes dye to color it. I really would like to leave it aluminum colored but if I can dye it, it means the surface structure has become porous and indeed my experiment worked.

All these parts are to a triple clutch I made for 1/4" lines. I had bronze bushings pressed into the cam arms but it seems to be a bad thing to have any other type of metal touching your to be anodized parts, so I took them out for the anodizing. I also had a solution of aluminum brightener so I cleaned my parts with that and rinsed them in water before putting them in.

It's all set up for tomorrow, it's 3 am and this will take 2 or 3 hours to complete. So I will post the results when I get around to doing this tomorrow.

 

[Dan H]

I've been thinking of doing the exact same thing. It looks like a great science experiment and I look forward to seeing your results.

 

[Zaphro]

I've used a similar method for removing rust from metal with excellent results.
http://www.acephalous.net/Jeep5.htm

 

[Bill1565]

Please, please move it outside.

 

[lyra7]

Looking forward to seeing the results. The variety of colors with aluminum is amazing. Now, how about the mast?

 

[Hermit Scott]

I used 60 ounces of battery electrolyte. I dumped two batteries out into a bucket settled out the sediment, then transferred into mason jars. Let it settle again and then poured into the inner bucket. I used almost 2 gallons of purified water to raise the level up above my parts.
I intended to use as little water as possible because I am shooting from the hip here. I put 5 lbs. of ice in the outer cooler and closed the lid. It has a little room to vent because of the wires going in.
I turned on the battery charger to the 2 amp setting. Bubbles immediately started to form on the cathode, 6061 aluminum plates on the sides of the tub. I changed the battery charger to 10 amps. But the meter still reads 2 amps.
I started at 16:30 Texas time.
I am giving exact measurements because if it works I want us to have a reproducible process.
So...we're off and running.

 

[Hermit Scott]

30 minutes into this now. There was a lot of foaming on top of the electrolyte. I added more purified water(1/2 gallon) and as much ice to the container as it would hold. I got my thermometer, but it starts at 130F. I really wanted to know the temperature.

 

[Dan H]

I've used a similar method for removing rust from metal with excellent results.

So did I on a big 4 jaw chuck for my old lathe. I wasn't able to get the amps up so it was slow long process. I think I need to use larger power supply, most likely connecting a battery in parallel to the charger.
Eager to see how this turns out.
Be careful.

 

[Bill Roosa]

Getting the current up

The reaction is a voltaic cell and only operates at a set voltage no matter how much voltage you put across it. To increase the amps you need to increase the size of the reacting surfaces.

 

[Dan H]

That's what I thought also Bill. The chuck is a 16" diameter chuck and I had two 2" x 8" plates for cathodes. I think what happened to me was the charger is restricted electronically, somehow. I switched it to 10 amps and is just putted along at 2 amps. Does the surface area of the anode and cathode need to be matched?

 

[Hermit Scott]

I took the parts out rinsed them and put them in dye mixed to double concentration on the stove in a SS pot. I don't know if it worked. There was plenty of bubbling though, so something happened. There were black flecks all over the parts and there is a white foamy substance on the top of the electrolyte.
I am dying them black so if that black is something cosmetic it may be covered anyway.
I put 3 more parts in that go to a deck organizer They were sanded and not polished. I think I may have contaminated the others by polishing them with a wheel I used on steel. I'll know that's it if these come out with out black flecks.

 

[Hermit Scott]

I think I know what I did wrong. I had copper tubes attached to the cathode. When I added more water the level went above the copper so it was in the solution. I pulled them up out of the water. I will see how this batch goes.

 

[Hermit Scott]

The black flecks are actually pits in the metal. Sections of the parts are anodized and sections aren't. The yellow streaks are the anodized sections. I have no idea why there are pits in these parts. I need to get new sulfuric acid and do these over. Experiment failed.

 

[sinnettc]

Interesting dicusssion/project. Did you add the dye to the sufuric acid mix? a bit of surfing suggests the dye part happens during the hot water bath after the sulfuric acid part.

 

[jibes138]

Maybe embedded iron

If there is any iron present it will react in the solution and cause pits and turn black. I used to shotpeen an aluminum part and the first time I anodized it the entire part turned black and corroded. We implemented a chemical process for removing the iron prior to anodize. in your case stay away from buffing wheels with iron and might be best to use scotchbrite or other fresh material to clean the surfaces. Anodize is non-conductive so you can easily check it, but how wil you know it is thick enough?

 

[Hermit Scott]

sinnettc-it looks like you can dye them either way.

jibes-Since the parts aren't being used for a cylinder liner or some ultra precise part, anything on the outside will be better than nothing.

I really need to do some practice runs. I ruined those parts. That clutch was a lot of work. The first few times are practice anyway when making something I haven't done before.

 

[Snotter]

I really need to do some practice runs. I ruined those parts. That clutch was a lot of work. The first few times are practice anyway when making something I haven't done before.

That is too bad you ruined the parts. The clutch looked awesome. I am following this thread with great interest and appreciate you taking the time to share what you are learning with us all.

 

[Hermit Scott]

That is too bad you ruined the parts. The clutch looked awesome. I am following this thread with great interest and appreciate you taking the time to share what you are learning with us all.

Thanks for taking an interest in my experiment. I was so sure it would work I didn't even check with a test piece.
I'm sick of working in the shop. I am going to work on the boat at the coast now.

Jibes do you know what the process was to remove the iron? It should be some kind of chemical bath. The iron is microscopic.

I am 100% positive that the edge with these tapped holes was not touched at all with a sanding disc or buffer, just sand paper. The big plate for the deck organizer was buffed. But it seems the sides of the big plates that were closest to the anode were the ones that got it the worst. All the little darker grey spots are significant pits. I am going to find an anodizing shop and pick someone's brain before I go any further. I do want to start out with new sulfuric acid so I know the exact concentrations.

 

[Ross]

I think that sodium hydroxide removes rust from steel plate. But it also reacts strongly with aluminum. maybe try phosphoric acid.

 

[jibes138]

Iron Decontamination

It was back in the 1980's but I'll look it up tomorrow and get back to you if you can wait that long. I'll check out the anodize spec also so you can know the concentration, voltages, ec.