How to Sand Aluminum: Dry Sanding Guide (Large Surface Workflow)

Aluminum can look flawless after sanding, but metal punishes the wrong grit: deep scratches, heat tint, or a cloudy finish. This guide walks you through a controlled grit progression to improve adhesion—with pressure, lubrication, and inspection tips so each step actually removes the previous scratches.

Why Sanding Matters

On metal, sanding isn’t just “making it smooth.” You’re creating a consistent scratch pattern that either (1) bonds to a coating between coats, or (2) refines to a polish-ready surface. The fastest path is a steady progression—each grit removes the scratches from the prior grit, then you move on. Jumping too far leaves random deep marks that reappear after wiping or polishing.

Recommended Tools

• Sanding block or flexible hand pad (for flat areas and even pressure)
• Soft backing pad for curves/contours (foam interface helps)
• Spray bottle with water + a drop of dish soap (for wet sanding)
• Degreaser or isopropyl alcohol and lint-free towels
• Masking tape (to protect edges, logos, or adjacent finishes)
• Good lighting: raking light or a headlamp to reveal scratch direction

Recommended Grit Sequence

• 80 grit
• 120 grit
• 180 grit
• 220 grit
• 320 grit

Step-by-Step

1. Clean and inspect. Remove oils and grime with degreaser, then dry. Mark the worst defects with tape so you don’t over-sand the whole part.
2. Set your scratch direction. Pick one direction for your first grit (e.g., left-to-right). Every next grit sands at a slight cross-angle so you can see when old scratches are gone.
3. Start your cut (light pressure). Use 120 Grit (25-pack). Keep the sheet flat on a block for flat panels; for curves, wrap around a soft pad. Let the abrasive do the work—pressing harder makes deeper scratches and heats the metal.
4. Use wet sanding when dust or heat is a problem. Mist the surface and paper lightly. If slurry gets thick, wipe and re-mist. Wet sanding reduces loading and helps you see the scratch pattern.
5. Refine the scratches. Switch to 220 Grit (50-pack). Sand at ~90° to the previous direction. Stop only when you can’t find any of the prior grit’s scratches under bright, angled light.
6. Finish the sanding stage. Use 320 Grit (100-pack) to unify the surface. Keep strokes long and even; for small parts, fold the sheet to keep a crisp edge without gouging.
7. Wipe, re-check, repeat if needed. Dry the surface completely—water can hide scratches. If you still see deeper lines, step back one grit and rework that area.
8. Stop at the right point for your goal. For between-coats, you’re looking for a uniform dullness; for polishing, you want a tight, consistent scratch haze with no random deep marks.

Special Cases

Edges and corners: They sand faster than flats. Tape sharp edges or use fewer strokes there to avoid rounding.

Heat-sensitive finishes: Stainless and aluminum can show heat tint if you dry-sand aggressively. Use lighter pressure and wet sanding for control.

Contoured parts: Use a soft backing so the abrasive follows the curve instead of creating flat spots.

Pro Tips

• Change sheets as soon as cutting slows—dull paper increases pressure and scratches.
• Keep your scratch direction consistent per grit; “random” strokes make inspection harder.
• Rinse or wipe slurry often in wet sanding to avoid dragging debris across the surface.
• Use raking light (light at a low angle) to spot the last few deep scratches quickly.

Aftercare

• Rinse and dry thoroughly; trapped water can cause spotting or flash rust on some metals.
• Wipe with alcohol to remove residue before coating or polishing.
• If coating, follow the coating’s recoat window and tack-wipe before applying the next layer.
• Store leftover sheets flat and dry to keep them ready for the next job.

FAQs

• Do I have to wet sand? Not always. Wet sanding helps when dust control, loading, or heat is a concern—especially on stainless and aluminum.
• How long should I sand with each grit? Until the previous grit’s scratches are fully removed. Time varies; inspection matters more than minutes.
• Why do scratches “reappear” after wiping? Water or solvent can temporarily mask deeper scratches. Always dry fully and re-check under angled light.
• Can I skip grits? You can, but it usually costs time. Smaller jumps keep the process predictable and reduce the chance of random deep marks.

Watch & Learn

Tip while you watch: pause the video at each grit change and compare the scratch direction on-screen to your work—if your scratches aren’t consistent, slow down and re-level before moving up.

Need the right sheets ready for the next step? Browse the full grit lineup here: https://equalle.com/collections/all.