Answer
For aluminum boat paint prep, use 120 or 180 on old coating edges, then 220 or 320 before primer.
Why it happens
Aluminum needs oxidation removal, scuffing, and cleaning before marine primer or paint.
Recommended grit
Use 120 or 180 for old coating edges, then 220 or 320 for primer prep.
Wet or dry
Dry for prep; wet only where the paint system allows.
Success check
The aluminum is clean, dull, and ready for marine primer.
What to do
- Clean the aluminum hull.
- Remove oxidation and loose coating.
- Sand old coating edges with 120 or 180.
- Refine with 220 or 320 before primer.
Avoid: Do not paint over oxidation or salt residue.