How to Sand Metal

Sanding metal removes rust and improves the appearance of the material. Well-sanded metal not only looks great, but it is also ready to accept paint or another finish. In this article, I’ll teach you how to sand metal, the different tools you can use to sand metal, and how to finish sanded metal.

How to Sand Metal

Each time you sand metal, follow these steps to transform rusty, crusty metal into a smooth, shiny, and rust-free surface.

1. Clean the metal. Remove grease, sap, dirt, or other debris from the metal. A wire brush will help scuff off any loose flakes of rust. Wipe the metal with a degreaser or detergent.
2. Put on protective gear. The abrasive action of sanding metal can produce sparks or turn metal splinters into projectiles. Cover your skin with long sleeves and pants. Don safety glasses or a full-face shield.
3. Choose your sanding tool(s). There are several tools that can be used effectively to sand metal. See the section below on metal sanding tools to help guide your decision.
4. Use good sanding technique. If using a powered sanding method, avoid pressing or leaning on the tool. Allow the tool to do the work. If sanding by hand, adjust the workpiece to an appropriate height to avoid back strain.
5. Dislodge thick rust. Use an aggressive abrasive material to break through caked-on rust. If your sanding tool requires sandpaper, start with 60 or 80-grit. With an angle grinder, you can use a wire wheel attachment or a 60-80 grit flap disc.

60 or 80 grit abrasive material will aggressively remove rust from the metal. If overused, it could damage or weaken the metal surface. Avoid this by switching to a 100-grit sanding paper or flap disc once the thickest rust is removed.

Moreover, continue sanding until all rust has been removed.

6. Improve the surface. Use an abrasive material with a grit of between 120 and 180 to remove imperfections from the surface of the metal. Sanding paper or flap discs of this grit level can remove scratches and gouges, as well as smooth rough edges.
7. Sand stubborn areas by hand. The sanding tool of your choice may not be able to reach every crevice and corner of your metal workpiece. Folded sandpaper can reach into tight corners or grooves.
8. Finish to desired sheen and smoothness. When the entire surface of the metal has been sanded with 180-grit abrasive material, it should be free of rust and previous finishes. The metal should feel smooth to the touch and is ready to accept paint or sealer.

Further sanding may be required to achieve super-smooth metal or a high-sheen surface. Consult the section below for ideas about how to finish sanded metal.

Polish the metal. If you’re leaving the metal unfinished, you may want to polish it for a super-smooth finish. Metal can be polished with very high-grit sanding material. Start with 320-grit sanding paper or flap discs. Continue raising the grit until you achieve the desired result.

9. Rub with steel wool. Sanding metal leaves behind marks. If you don’t like the appearance of these marks, you can buff them out using fine-grained steel wool. Rub the steel wool over the surface in a circular motion.

Sanded Metal Finishes

Metal that is smooth to the touch is ready to be finished. Learn how to accomplish four sanded metal finishes.

Rubbed

The easiest way to finish sanded metal is to rub the sanding marks out using ultra-fine steel wool. Fold the steel wool into a pad and rub it in circles over the surface of the metal.

Polished

To polish metal, continue sanding using progressively higher-grit sanding paper. Use a light touch to avoid scratching the metal. Sanding paper is available in grits up to 7000, but 1200 grit is enough for most consumer purposes.

Wet-Sanded

Wet sanding is a refinishing method used to make metal very shiny. This gentle sanding method is great for removing small scratches and previous sanding marks.

Wet sanding is best accomplished with very high-grit sanding paper and an orbital sander. The sanding paper must be designed specifically for wet-sanding.

When wet sanding, the paper is dipped in water before being applied to the metal surface. A spray bottle of water is used to keep the metal surface wet during sanding. This keeps the sandpaper from getting clogged and creating deep scratches.

Wet sanding allows you to achieve a gleaming, scratch-free surface.

Start wet sanding with 180 grit wet sandpaper, and move up until you’ve achieved the finish you desire. Wet sanding paper is available in grits up to 7000 for an extremely smooth and shiny finish.

Metal Sanding Tools

Four tools that can be used to sand metal are the orbital sander, sanding block, angle grinder, and belt sander. Each has its own benefits and drawbacks. Read on to learn which metal sanding tool is best for your project.

Orbital Sander

Orbital sanders use specially-shaped sanding discs to remove material from metal or other surfaces. The head of this power tool moves in small circles, which tend to leave less obvious sanding marks than an aggressive angle grinder.

Angle Grinder

Angle grinders are powerful tools that can be used to sand, shape, or even cut through metal. This aggressive removal tool is best suited to the early stages of sanding, such as rust removal, and grinding down sharp edges.

To sand metal using an angle grinder, you must choose an appropriate attachment.

• Wire wheel attachments are best for clearing rust from corners or grooves.
• Wire cup brushes can be used to sand flat or curved surfaces.
• Flap discs or flap wheels feature cloth flaps studded with abrasive material. Like sandpaper, they are categorized by grit.

Sanding Block

A handheld sanding block can also be used to sand metal.

This method requires more physical effort than using a power tool, and the process will take longer.

You can wrap sanding paper around a block of wood for a make-shift sanding block, or purchase a purpose-built sanding block.

Belt Sander

A belt sander is not the best tool for sanding metal, but it can be used for this purpose.

Belt sanders are very aggressive and remove a lot of material quickly. When sanding metal with a belt sander, be very careful not to remove too much material. Removing too much material while sanding metal can result in weakened or even damaged metal.

If you must use a belt sander to remove rust or an existing finish, switch to another tool when the rust or finish is almost gone to avoid weakening your metal.

Do You Need Special Sandpaper for Metal?

Unless you are wet-sanding, you do not need special sandpaper for metal. The same sandpaper you use to prepare wood can be used to sand metal.

• Very rough surfaces should be sanded with coarse-grained sanding paper of 60 or 80 grit.
• Once the roughest areas have been smoothed, switch to 100 grit sanding paper to avoid excessive material removal.
• 120-180 grit sandpaper is used to prepare metal surfaces to accept paint or sealant.
• Extremely fine sandpaper with grit over 320 can be used to polish metal surfaces.
• If you are finishing sanded metal by wet sanding, you will need to switch to sanding paper designed for this purpose.

Conclusion

Metal can be sanded to remove rust, smooth out imperfections, or achieve aesthetic and design goals. You can use an orbital sander, angle grinder, or sanding block to sand metal. Sanded metal can be rubbed, polished, or wet-sanded to achieve a smoother finish.