Answer
For cast aluminum patio furniture, use 180 or 220 on corrosion, then 320 or 400 before primer.
Why it happens
Cast aluminum needs oxidation removal and scuff sanding before primer or paint.
Recommended grit
Use 180 or 220 for corrosion spots, then 320 or 400 for smoother paint prep.
Wet or dry
Dry.
Success check
The aluminum is clean, dull, and ready for primer.
What to do
- Clean the furniture first.
- Sand corrosion spots with 180 or 220.
- Scuff the full surface with 320.
- Use 400 for smoother visible areas before primer.
Avoid: Do not paint over chalky oxidation.