Step 4: Anodising your part
The way I did it was by only inserting half the piece, and every ten minutes or so rotating it, so it ended up coating evenly enough.
Any part that touches the bottom or sides of the container also will not be anodized.
Run it. Let your piece sit in the bath for an hour or more.
- Bubbles will form. This is normal, and it is the formation of Oxygen gam at the Anode that makes the process work.
- Your solution may heat up as well. This isn't desirable as it will cause different speed plating, and so different size 'pores.' The only way I can see to offset this is to only run it for shorter periods at a time, and have a big container that will hold coolness for longer. I never noticed this as a problem, but if you are doing it commercially it might be.
If you remove the part from the bath and clean off the bubbles you will see that the object has gone matte. This is because the surface is now pitted with tiny little holes in a layer of the darker Aluminium oxide. When the layer is only thin, this can be scratched off with anything metal. When it is thicker it still can, you just don't notice it so much!
Finally remove the part from the bath, and rub it with some toilet paper to remove the lemon juice.