Anodising.

[th62]

A bit of anodising done today. One side was mirror polished, the other garnet blasted. I skipped the etching process to see if I could retain the shine, or at least some shine, no go. Nevertheless, it does provide a good finish for parts made of aluminium that don't need to be polished. My anodising setup is pretty basic: 10 litre plastic tub. Diluted sulfuric acid. Aluminium cathodes, aluminium wire and 10 amp battery charger. Before doing anymore I'll upgrade to lead cathodes, an ammeter and some titanium wire. I can also try a thinner anodise coating, if nothing else, it will give a lighter grey colour.

For the shiny parts, I investigated bright dipping, but the process is far to toxic and dangerous for me, and there are very few places that do it commercially, due to that.. So ,I'll give electro polishing a go instead. Not sure if oxidising is a problem after this procedure, information is a little sketchy in this area.

[DIYer]

Thanks th62! We've added your Anodizing Setup to our Metalworking category,
as well as to your builder page: th62's Homemade Tools. Your receipt:

Anodizing Setup by th62

tags: anodizing

[meyer77]

A few questions, if you don't mind. I have read to use lye to clean the parts but when I tried the aluminum turned black. Is that because of the alloy?
I did get a quart of desmut solution a while back but have not had a chance to use it yet.
Did you have any trouble with the battery charger shutting down, because it wasn't charging a battery?

[th62]

I've never heard of using lye. Using a caustic solution is not necessary, just make sure you clean the aluminium in acetone and soap and water several times before dunking in the anodising bath. The cleaning is the most important process. Do not touch with bare hands! My battery charger has a power supply mode so switching off and on isn't a problem. You can modify a battery charger to stop it switching, I did that years ago with a small one I wanted to use as a transformer, google it.

[greenie]

DO NOT use Lye, or as it's called elsewhere - Caustic Soda, if you leave the ally part in the Lye mix it, will start to dissolve/eat the ally away.

[th62]

No, that is incorrect. Caustic soda is normally used to prepare the aluminium surface for anodising. That is the normal process; however, as I said it is not necessary.

Lye, baking soda and caustic soda are all caustic, but lye and caustic soda are very aggressive. Use baking soda preferably, but briefly, if you wish to use it. I skip this process.

Google is your friend, there are a plethora of sites on DIY anodising. Caswell, has a site, they also sell kits and have a 'how to' page...

[greenie]

I will have to agree, to disagree, with your above statements.

If you check up on what LYE and Caustic Soda are made of, you will find that they are the exact same item, only difference is what they are called in different countries.

They both are Sodium Hydroxide, and one use of Caustic Soda is in the production of Aluminium, now if you make up a brew of Sodium Hydroxide and drop in a piece of Aluminium, leave it in the solution for 24 hrs, remove it and visually check the the item, you will soon see that a lot of the surface has been eaten away by the chemical reaction of the Sodium Hydroxide.

If you make the brew in a 2 gallon plastic bucket, tip the whole container full of flakes into the water and stir it until the Crystals dissolve, then drop said item into the brew. Please do a test before answering this and if anybody cares to repeat this very simple exercise, then please do and let everybody know what has eventuated. :-)


https://en.wikipedia.org/wiki/Sodium_hydroxide

[meyer77]

That is the problem with the internet, everybody has a different method.
From what I have read different alloys will react differently. Mine turned black real quick (less than 5 minutes). I did buy a quart of "desmut" concentrate but have not used it yet. I am not set up to do any anodising yet.

[Frank S]

One of the major factors in how certain chemicals effect different things is the concentration and dilution ratios
Caustic soda at 10% concentrate when combined with bitumen injected into the ground becomes a soil stabilizer for building construction
Higher concentrations of caustic soda can cause an adverse reaction out gassing into the concrete.
The same holds true when using it as a catalyst or activator in the anodizing process too little yields poor results too much leads to possibly destroying what you are wanting to protect.

[th62]

I would suggest you read my post again, I just said they are all caustic. Now 24 hours, you gotta be kidding, when anodising, if you use a caustic solution, you dunk the ally in the solution for a couple of minutes. 24hours, I'm surprised there was anything left!

I would suggest before you do any more work read up on it!