How to Sand Metal Surfaces for Welding & Fabrication (60, 100, 150, 220 Grit Guide)

Preparing metal before welding or fabrication is critical for strong, clean joints. Rust, mill scale, and paint residues can compromise weld quality and lead to weak bonds. With the correct grit sequence, you can create a clean, properly textured surface that ensures strong adhesion and professional results.

Why Sanding Metal Matters Before Welding

Metal surfaces accumulate rust, oxidation, or old coatings that interfere with weld penetration. Sanding provides a fresh, smooth surface while giving just enough texture for proper bonding and finishing.

Tools & Supplies

• Angle grinder or sanding block
• Wire brush (for pre-cleaning)
• Dust mask & safety glasses
• Shop vacuum for cleanup
• Welding gloves and protective gear

Recommended Grit Sequence for Metal Prep

• 60 grit: Aggressive removal of rust, scale, and old paint.
• 100 grit: Leveling surfaces and reducing coarse scratches.
• 150 grit: Smoothing weld zones before fabrication.
• 220 grit: Final prep for clean, smooth metal ready to weld or coat.

Step-by-Step: Sanding Metal Before Welding

1. Initial cleaning. Remove grease, oil, and heavy rust with a wire brush or degreaser.
2. Coarse sanding. Use 60 grit (25-pack) for fast removal of scale, rust, and stubborn coatings.
3. Smooth surface. Switch to 100 grit (100-pack) to even out the surface while maintaining texture for weld penetration.
4. Refine weld areas. Sand with 150 grit (50-pack) to prepare weld seams and edges.
5. Final pass. Finish with 220 grit (25-pack) for a clean, consistent surface ready for welding or painting.
6. Cleanup. Vacuum and wipe down with a tack cloth to remove sanding dust before starting work.

Special Cases

• Thick rust layers: Start with a grinder, then follow with 60 grit sanding.
• Thin sheet metal: Avoid heavy pressure with coarse grits to prevent warping.
• Polished finishes: Continue beyond 220 grit (up to 400) if a reflective finish is desired post-welding.

Pro Tips

• Always sand in overlapping strokes for uniform prep.
• Use wet/dry sandpaper with water to minimize dust when refining at 150–220 grit.
• Keep weld zones slightly rough (not polished) for better penetration.
• Re-clean with acetone or alcohol before welding for the best results.

Aftercare

• After welding, re-sand with 150–220 grit to smooth weld beads.
• Apply rust-inhibiting primer if metal will be exposed to air.
• Store sanded metal in a dry environment before use.

FAQs

• Can I weld without sanding? Not recommended—contaminants reduce weld strength and appearance.
• Should I polish before welding? No. Leave slight texture (150–220 grit) for stronger bonds.
• Is wire brushing enough? For light oxidation, yes, but sanding ensures complete prep.

Watch & Learn

Sanding metal properly ensures clean, strong welds and reduces rework. Stock up on 60 to 220 grit sandpaper sheets in multiple pack sizes for welding and fabrication projects. Explore the full metal sanding collection today.