Final answer:
Alodine is used on aluminum to increase corrosion resistance and to create a porous oxide layer that can be dyed for coloration. The anodizing process builds up an oxide film that can be sealed for additional protection.
Step-by-step explanation:
The desired effects of using Alodine on aluminum alloy include enhancing the material's corrosion resistance and creating a porous surface that can absorb dyes for coloration. The process of anodizing, by etching the aluminum with sodium hydroxide and then using it as an anode in dilute sulfuric acid electrolysis, allows for the buildup of an oxide film. This oxide layer can be further treated to become non-porous, providing additional protection against corrosion and wear.