How to Sand Metal Before Painting: Rust Removal & Smooth Finish (80–400 Grit Guide)

Painting over metal without proper prep leads to peeling, chipping, and rust returning. The secret to a lasting, smooth finish is thorough sanding in the correct grit sequence—plus the right primer. This guide walks you through how to sand metal for painting, from rust removal to final surface prep.

Why Sand Metal Before Painting?

Sanding removes rust, flaking paint, and surface oxidation while creating a texture that primer can grip. Skipping this step means your new paint may fail prematurely.

Tools & Materials

• Degreaser or cleaner
• Rags or tack cloth
• Wire brush or wheel
• Sandpaper in multiple grits
• Rust-inhibiting primer
• Paint of choice

Best Grit Sequence

• 80 grit — Heavy rust removal and stripping old paint.
• 120 grit — Smoothing after rust removal.
• 220 grit — Final shaping before primer.
• 320–400 grit — Ultra-smooth finish for topcoats.

Step-by-Step: Sanding Metal for Painting

1. Clean the surface. Remove grease, oils, and dirt with a degreaser or cleaner. This prevents contamination under the paint.
2. Remove heavy rust. Start with Grit 80 (25-pack) to quickly cut through thick corrosion or peeling paint. For stubborn rust, pair with a wire brush or wheel.
3. Smooth with 120 grit. Switch to Grit 120 (50-pack) to refine the surface, blend edges, and remove deep sanding scratches left by the coarse grit.
4. Refine with 220 grit. Use Grit 220 (100-pack) to create a uniform texture that promotes strong primer adhesion.
5. Finish with 320–400 grit. For glossy paint jobs, wet sand with Grit 400 (10-pack) to achieve a smooth, glass-like base before topcoating.
6. Clean again. Wipe down the surface with solvent or tack cloth to remove dust and residue.
7. Prime & paint. Apply a rust-inhibiting primer, let it cure fully, then apply your chosen paint in thin, even coats.

Pro Tips

• Always wear a respirator mask—metal dust is hazardous.
• Use wet/dry sandpaper for finer grits to reduce dust and clogging.
• Wrap sandpaper around a foam pad for even pressure on curved areas.

Aftercare

• Store metal items in a dry environment to prevent new rust.
• Inspect painted surfaces annually and touch up chips immediately.

FAQs

• Can I sand aluminum the same way? Yes, but avoid aggressive grits like 80 unless removing heavy oxidation.
• Do I need to wet sand metal? Only for the finest grits (320–400) before topcoat for a high-gloss finish.

Watch & Learn

By following this grit sequence and proper prep steps, you’ll ensure your paint job lasts for years—whether on outdoor furniture, gates, or automotive panels.