What is meant by anodising? How is it done?

(N/A) Anodising is an electrolytic process used to increase the thickness of the natural oxide layer on the surface of metal parts,typically aluminium.
During this process,a clean aluminium article is made the anode and is electrolysed with dilute sulphuric acid.
The oxygen gas evolved at the anode reacts with the aluminium to form a thicker,protective aluminium oxide layer,which makes the metal resistant to corrosion.