How to Sand Car Primer Before Painting (320, 400, 600, 800 Grit Guide)

Primer is the foundation of every great automotive paint job. To ensure flawless adhesion and smooth topcoats, sanding primer is essential. With the correct grit sequence, you’ll create a uniform surface that’s ready for basecoat and clear coat. This guide explains how to sand automotive primer step by step using 320, 400, 600, and 800 grit sandpaper.

Why Sanding Primer Matters

Primer often dries with slight texture or imperfections. Sanding removes dust nibs, levels high spots, and opens the surface for better adhesion. Without sanding, paint may not bond properly, leading to peeling, orange peel, or visible scratches.

Tools You’ll Need

• 320–800 grit wet/dry sandpaper – ideal for step-by-step refinement.
• Sanding block – ensures flat, even pressure.
• Water spray bottle – prevents clogging on finer grits.
• Tack cloth & microfiber towels – remove dust between stages.
• Automotive primer & paint – for sealing after sanding.

Best Grit Sequence for Primer Sanding

• 320 grit: Knocks down rough texture and high spots.
• 400 grit: Smooths surface and removes scratches.
• 600 grit: Prepares primer for basecoat application.
• 800 grit: Final sanding for high-gloss or metallic finishes.

Step-by-Step Process

1. Begin with 320 grit. Level primer texture with 320 grit (25-pack).
2. Smooth with 400 grit. Refine surface scratches using 400 grit (100-pack).
3. Refine with 600 grit. Wet sand evenly with 600 grit (50-pack) for basecoat prep.
4. Finish with 800 grit. Use 800 grit (25-pack) for a smooth, paint-ready finish.
5. Clean thoroughly. Wipe with a tack cloth before applying basecoat.

Special Cases

For high-build primers, start coarser at 220 grit before moving to 320. For thin primer coats, avoid sanding too aggressively—stick with 400 and up. Metallic paints benefit from finishing at 800 grit for the smoothest reflection.

Pro Tips

• Always wet sand finer grits to avoid clogging and scratches.
• Sand in straight lines, not circles, for even results.
• Keep the surface clean—primer dust can cause scratches if left behind.
• Check under bright light to ensure uniform dullness before painting.

Aftercare

• Apply basecoat and clear coat immediately after sanding to prevent contamination.
• Store unused sandpaper flat and dry for best performance.
• Inspect the surface carefully—small imperfections become obvious once paint is applied.

FAQs

• Do I need to sand between primer coats? Yes, lightly with 400–600 grit for best adhesion.
• Can I paint directly over unsanded primer? Not recommended—paint may not bond properly.
• Is 800 grit too fine? No—800 grit is perfect for final sanding before high-gloss finishes.

Watch & Learn

For flawless primer prep, explore our metal sanding collection.