Sanding painted metal is a crucial step for proper surface preparation before applying a new finish or repairing existing paint. The correct approach depends on the condition of the paint you are working with.
## Why Sand Painted Metal?
Sanding painted metal serves two primary purposes:
* **Removing Damaged Paint:** If the existing paint is peeling, cracked, or significantly damaged, sanding helps to remove the compromised layer down to a stable surface.
* **Providing a "Key" for New Paint:** Even if the paint is in good condition, sanding creates microscopic scratches (a "profile") on the surface. This rougher texture allows new paint or primer to adhere better, preventing future peeling or chipping.
## Choosing the Right Sandpaper Grit
According to the provided reference, selecting the appropriate grit of sandpaper is essential for achieving the desired result on painted metal:
* **For Damaged Paint:** Use **120 grit sandpaper** to effectively remove any damaged paint. This coarser grit is aggressive enough to strip away compromised layers.
* **For Paint in Good Condition:** Use **240 grit sandpaper** to simply roughen the surface. This finer grit will scuff the existing paint without removing it entirely, preparing it for better adhesion of subsequent coatings.
Here's a quick summary:
| Paint Condition | Purpose | Recommended Sandpaper Grit |
| :------------------- | :----------------------- | :------------------------- |
| Damaged Paint | Remove Paint | 120 grit |
| Paint in Good Condition | Roughen/Scuff Surface | 240 grit |
*Note: The reference also mentions using 120 grit sandpaper for bare metal, but for painted metal, the choice depends specifically on the paint's condition as detailed above.*
## The Sanding Process
Once you've chosen the correct grit, the general process involves:
1. **Cleaning:** Thoroughly clean the metal surface to remove dirt, grease, and rust.
2. **Sanding:** Begin sanding using your chosen grit.
* For damaged areas, focus on removing the compromised paint.
* For good condition paint, lightly scuff the entire surface to dull the shine.
3. **Wiping:** Wipe down the sanded surface with a tack cloth or damp rag to remove dust.
4. **Inspection:** Check the surface to ensure you have achieved the desired result (removed damaged paint or uniformly scuffed the surface). Repeat sanding in areas if necessary.
Sanding can be done manually with sandpaper sheets or using power tools like orbital sanders for larger areas. Always wear appropriate personal protective equipment, including gloves and a dust mask or respirator.
Properly sanding painted metal ensures that your new paint application will be durable and look professional.
