Answer
For a metal mailbox, use 120 or 180 on rust, then 220 or 320 before primer or paint.
Why it happens
Outdoor metal needs rust removal and light scuffing before primer or paint.
Recommended grit
Use 120 or 180 on rust spots, then 220 or 320 for paint prep.
Wet or dry
Dry.
Success check
The mailbox is clean, dull, and ready for primer.
What to do
- Clean dirt and residue from the mailbox.
- Sand rust spots with 120 or 180.
- Scuff the full surface with 220 or 320.
- Remove dust before primer or paint.
Avoid: Do not paint over rust, dust, or glossy old coating.