Anodising is a process used to improve the appearance and durability of aluminium articles. Which of the following statements best explains the principle behind anodising?
Aluminium is made the anode and oxidised to form a thicker protective oxide layer.
Anodising is an electrolytic process carried out in a dilute acid bath in which the aluminium article is made the anode. When a current is passed, oxygen produced at the anode reacts with the surface aluminium to form a thick, hard and adherent layer of aluminium oxide.
This artificially produced oxide layer is much thicker than the natural one and protects the metal from further corrosion, while also providing a surface that can be dyed for a better appearance. Aluminium is not being coated with zinc, not being made the cathode, and not being dipped in alkali to make it more reactive; the whole point is to make it less reactive by growing a protective oxide.
Hence, the answer is Aluminium is made the anode and oxidised to form a thicker protective oxide layer.
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