The anodization of aluminium objects is a process that gives to the same not only a more agreeable aspect, but also a greater hardness and resistance.

For a good anodization, it is opportune to prepare previously the pieces to be anodized dipping them in a bath lukewarm water with caustic soda. 
By means of this bath the pieces become opaque, being the opacity a function of the time. Then wash abundantly, without touching them with your hands.

Prepare separately a plastic container and fill up it with a liter of electrolyte for batteries (sulfuric acid with distilled water), using gloves and goggles.

Dip in the solution a lead piece (cathode), and connect it to the negative pole of a 12 V battery. The piece to be anodized (anode) should instead be connected to the positive pole. Both pieces must be suspended by means of aluminum threads.

As soon as begun the process, it will be possible to observe in the solution the flow of the ions.
After half an hour the process will be finished, and it will be possible to remove the piece from the bath.

To this point, if you want, you can proceed to its dye, generally in black.
Once dry, in order to close the pores, you can submit the piece to a hot bath or vapor, with distilled water.

The images show the aspect of the objects in the three different phases of the process.