Anodising

[Janger]

Working on Anodising aluminium. After ruining many pieces I finally have some good results.

A few key learned details.
The electrical connection has to be solid. Make a jig or a threaded connection. Al wire is too brittle to connect firmly enough.

Use battery acid. People on the net claim other concoctions work. Not for me. Hard to find in Calgary. I bought mine in Montana. I can't confirm but I was told Gregs distributor has it here in town.

Make sure the dye is hot (60C+) before you put the part in. Don't let the part dry out before the dye bath. I just used liquid RIT fabric dye.

Good videos on the net on this topic.

Try to get the amperage correct. Buy big resistors and do the ohms law math.

 

[Kris Jensen]

Wow nice job!!

 

[PeterT]

Holy crap. You're a god. we need to talk!
(would like to seem more of your skunkworks: power supply, cleaning procedure, heated bath setup, typical times for parts like that)
When you say acid, do you mean solid chemicals to mix your own, or its already in liquid form?

 

[Janger]

Holy crap. You're a god. we need to talk!
(would like to seem more of your skunkworks: power supply, cleaning procedure, heated bath setup, typical times for parts like that)
When you say acid, do you mean solid chemicals to mix your own, or its already in liquid form?

Ok I'll put together some photos...

@Jwest7788 Next group event. A tour of a few shops. I could show anodising.... I'd like to see @Alexander cnc lathe and @Kris Jensen new plasma cnc....

 

[Janger]

ok a bunch of photos.

Andoising is making a layer of porous oxide on the outside of part. The pore space can then accept dye for coloring. It's fussy. Read my post above for the main gotchas I experienced.

Some commentary on the photos.

Threading the part and a Aluminium welding rod for a high quality electrical connection.

Try to make the part as shiny and clean as possible. Buff it. Sand it. Wash it in soap and water. Wear gloves when handling the part.

Cleaning the part by dipping in a somewhat strong solution of NaOH (lye) for a few minutes. I put 50g of lye into about 400ml of water. The powdered lye came from my spouse who makes soap. The next shot shows vigorous bubbling. Take it out, and rinse it thoroughly in distilled water. I use a trigger sprayer recycled from some cleaner.

The acid solution is diluted sulphuric acid from a battery top up package. Picture down at the end. Put acid into the water, not the other way around. Ratio is 1:4 acid to water. Use distilled water. Everywhere use distilled water. Be careful, wear gloves, and eye protection.

You can see my exhaust fan and the acid bath sitting under it. The acid has a strong odour and I imagine it's toxic. The exhaust fan really helps.

Make a wooden jig to grip the welding rod. Makes it really easy to attach the wires to the part and the cathode. Part takes the positive wire. Cathode (negative) is a big piece of aluminium with more welding Al rod wrapped around the bottom of the container.

The rule of thumb for current is 12A per square foot of material for one hour. Below you can see my resistor bank for limiting the current. After it's been in for an hour I typically remove the resistors and give it 10-15 finishing minutes at full blast. It seems to help. The part has a subtle yellowish cast if the anodising worked.

Power supply is a 24V 6A brute from B &E Electronics here in town. Active Electronics has similar gear. You don't need this much power. Current is typically well under an amp for little parts like this. I wanted a big one for another project.

 

[Janger]

More...
Power supply close up, and box of battery acid.

Ok and here's the high tech dye pot, using a double boiling approach. Get the dye good and hot 60C or more. I'm using a $4 pot from value village, none of the food pots here.... and Distilled water with RIT brand fabric dye (Michael's craft place, or fabric stores, or Walmart in USA). Purple this time. The part turned out quite pink. Distilled water reduces water spots. The water in the pot is also distilled. Heat up the dye while you're anodising. Then rinse the acid off the part with distilled water and head to the stove. Put the part in the hot dye. Wait. 10 15 20 minutes.... It sometimes takes a while for the dye to take, other times it's instant. Colour dependent? Once you are happy with the colour, then lock the dye in by putting the part in the boiling water. Wait. 10, 20 minutes? Steam works too so I just put the lid on and let it cook for a while.

Here is a close up and some results to look at. You can see any imperfections, scratches, unevenness tends to really show up. The better the surface the nicer the results. If you're really keen to do this, go watch some you tube videos, there's lots of good ones, then reread all this. I had about 8-10 attempts before I got all the details right and it started to work for me. Persevere! Enjoy!

 

[PeterT]

Thanks for taking the time to assemble the pics & share details. Wow, mad scientist stuff. Really interesting & demonstrates what a detailed process anodizing is. No wonder it costs.
Do you find that certain aluminum alloys anodize better or worse than others? (I heard 6061 is good but I think 7075 was worse).
So what are the parts?

 

[Janger]

The parts are 6061 tubing just for this experiment. I had some Al scrap which I can't seem to anodize. It might not be 6061 as it is hell to weld too.

It is a detailed process but do-able. When I make real Al parts I'm good to try to Anodize them. I'd like to try anodising a cast part and see if that works.

What do people charge to do this? Any past experience or knowledge?

 

[PeterT]

I'm dating myself back at least 15 years but I inquired about parts with roughly the same surface area as your rings. Seem to recall they were 4-$5-ish each if it was a color they happened to be doing & low parts count. The price went down with larger parts count batches. A lot of places impose a minimum or 'setup' charge in the $50-100 range, presumably for cleaning & prepping. Maybe best to just sent out a dummy quote to some local places. I've heard of people outsource to China, but that was usually in conjunction with also getting the parts made there. Results varied from really great & low shipping to the opposite.

 

[BradH]

Awesome stuff! Looks like good fun.

 

[Jwest7788]

@Janger This is all awesome. You really have some great colour figured out there. That red finish is worth paying for, learning the process is officially on my list, great job!

@Jwest7788 Next group event. A tour of a few shops. I could show anodising.... I'd like to see @Alexander cnc lathe and @Kris Jensen new plasma cnc....

Agreed, Touring town and seeing shops would be awesome. Maybe plan on a Saturday, start around 10:00 at a Tim's somewhere for coffee, get moving to shops and plan to grab lunch as a group?
I'm in, will open a separate thread and post a notice to see who's interested. If nothing else we should have a coffee shop meetup to see what everyone's been up to.

 

[Jwest7788]

Hey, Care to let me know when you plan on doing a batch of anodizing next? I have a single part that could look alot better black rather than plain ol' aluminum.

Let me know!

JW

 

[Janger]

Sure Josh! Although if you want to powder coat instead I've got a powdercoat gun setup in red and we could coat your part in less than an hour. See my new thread on powder coating.

 

[Bofobo]

I Just finished a throttle slide for my dirtbike, its steel and i dont know which would be better; anodize or powdercoat, its mostly concealed and im looking for rust protection over shinny factor. Suggestions?

 

[Jwest7788]

Try to get the amperage correct. Buy big resistors and do the ohms law math.

Hey, What was the amperage and voltage range you ended up settling into? I can find lots of charts online but curious as to your findings.

I Just finished a throttle slide for my dirtbike, its steel and i dont know which would be better; anodize or powdercoat, its mostly concealed and im looking for rust protection over shinny factor. Suggestions?

Nice, that looks awesome. If you ever have to remake it, I suspect that aluminum or Delrin might be better to avoid that issue in future.

Becuase it's a slide surface, I think powder coating would fail after awhile... Can you anodize steel?

Edit: Yup:

JW

 

[Janger]

I think a black oxide treatment might be best Mike. Simple. Durable. Or If you want to powder coat it we could do that at my shop.

Josh the anodizing voltage was 24V I don’t recall the current but I think it was 0.5A. quite low. Hence the resistors to limit it down. Less and slower worked better.

 

[Bofobo]

I watched a lot of videos yesterday and most anodizing was done with 6v batteries or car battery chargers. Its all in the amps, and lower around 1-2 amps does the trick.

I think a black oxide treatment might be best Mike. Simple. Durable. Or If you want to powder coat it we could do that at my shop.

how durable is the powder coat and how much volume will it add? The inside of the tube will be heavily worn over time but its mostly just a dry rust inhibitor im looking for as water and mud turn lubricants into a sticky paste and its not for a street bike which I could otherwise oil up to prevent slide - bar rusting or i would keep it unfinished. Made of steel because its what i had... could have cast an aluminum or brass one but i had this perfect piece from the group buy i brought to the cnc demo at Modern tool just begging so it became the rainy day project

 

[Dabbler]

another idea is to dip in to copper sulfate solution, which leaves a copper coating on the steel. It does protect from rust but has a green patina...

 

[Bofobo]

I thought about copper but remembering some nasty build ups ive seen on old pipes, i didnt think it would work out over the long run. I do however love the copper patina

 

[Janger]

Powder coat is like thick paint. Maybe 0.010”