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Anodising Aluminium - my setup that seems to have worked.

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raynerd:
I have recently been making a pen for my dad for Christmas and someone mentioned that I need to anodise it before I give it to him otherwise the surface will scratch too easily and be too soft. I haven`t ever looked into this and dipped my toe in the water for the first time yesterday with some success and then I did it again today, learning from my mistakes and improving my method. I`ve not looked into the Chemistry properly yet but since this is an electrolysis in 20% sulphuric acid, your basically breaking up acidified water into Hydrogen and Oxygen and since the aluminium is attached to the +ve anode where the oxygen is attracted to, I can only presume you are forcing oxidation of the surface of the aluminium. The cathode (-ve) is made from lead and allows the Hydrogen to form at the other side.

So the setup was very simple, a beaker, 1.5M Sulphuric Acid, power supply 12v maximum 4A, some wires and a lump of lead. I took pictures at each stage but just a little interesting bit to kick us off! The final oxide layer has pores in it until it is heat sealed. These pores allow you to add a stain into the pores and colour the aluminium with an organic dye. I tried this yesterday and stained my aluminium blue but I had a thought today, what if the stain dyed non-anodised aluminium and then my proof of anodising is lost!   

My scrap piece of ally, decent finish on one side not great on the other. Just a scrap from the metal bin.


Dipped in the dye for 5 minutes and removed


Success the dye washes off! This is fantastic, I now know that if my dye does stick at the end then I have anodized the piece (or at least done something interesting to it!)


This is the electrolysis cell – 12V, -ve connected to the lead and the acid in the beaker


Here it is bubbling away – you can`t see the bubbles on the picture but trust me, is was going!


With 12V running through it it starts to act like a heater and the water rises. This isn`t good because the final stage to “set” or harden the oxide is heating it at the end. We don`t want to heat it now or the layer won`t form properly. I simply sat the cell in a washing bowl of iced cold water to keep the acid cool.


After 45 minutes the aluminum piece was removed. It certainly feels different, it feels smoother and a touch cloudy on the surface maybe. I tried scratching it with a sharp edge and it did not scratch yet the bit unanodised at the top did.


The moment of truth, if I can stain this now and it wouldn`t before than I`ve clearly done something to it and presumably anodized it. This is an organic dye but I believe the cloth dyes you can pick up at Wilkinsons or Hobbyshops are excellent for this:


And then finally dipped into hot water to seal:


Not as blue as yesterday as the dye solution I made up wasn`t as strong but it has definitely taken it and looks really nice in the light. Clearly you don`t have to stain it, the point is it can be done but it also proves that I must have anaodised it to allow the stain to hold:


And then off to make a brew – it is cold outside!!


chris

Powder Keg:
Thanks for sharing Chris. That looks like fun! I might have to try it.

Rob.Wilson:
Hi Chris

Very interesting ,,,great job  :thumbup: :clap: :clap: :clap: :clap:,,would a computer power supply work ?  do you think it would be  possible to turn same PS into a variable one ?

Regards Rob

tinkerer:
Wow! Thanks for this, I had no idea that was all there was to anodizing. Do you think a marine 12v battery charger will be good enough for this? Where did you get the acid?

Can't wait to see the pen when finished.

Brass_Machine:
Hey Chris...

Making this a how to and moving there. I am going to have to give this a try.

Eric

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