Which of the following is a desired effect of Alodine on an aluminum alloy?

• A. A completely smooth painting surface
• B. Increased corrosion resistance
• C. Removal of all surface oxides
• D. Decreased adhesion of paint

Answer: (B)

Alodine is a chromate conversion coating used on aluminum alloys. It chemically converts the surface oxide into a thin protective aluminum chromate film. This layer provides increased resistance to corrosion by acting as a barrier to moisture and aggressive ions. It also helps paint adhere better because the coating creates a reactive, slightly textured surface with micro-porosities that primers can bond to. It doesn’t remove oxides, and it doesn’t produce a completely smooth surface; rather, it forms a protective layer and primes the surface for bonding. So the desired effect is increased corrosion resistance.