Do you find it frustrating when you’re finishing up a metal surface and can’t quite get that perfect shine to it? No matter how much you buff and polish it, something just isn’t working. The key to getting a mirror-like finish is by using a technique called wet sanding. Wet sanding removes all of the tiny imperfections that can leave metal looking dull and give you a professional looking surface.
In this guide, we go over how, when, and why you should wet sand metal surfaces. If you are just looking for more information about wet sanding, check out our previous blog post, What is Wet Sanding? Wet Sand FAQ.
Wet Sanding Basics
Wet sanding is a finishing technique that uses sandpaper and water, or another liquid, as a lubricant to smooth a surface. It is commonly used in automotive refinishing, metal fabrication, and other industries where a high-quality finish is desired.
The combination of the sandpaper and lubricant gradually removes material from the surface. The lubricant serves several purposes:
- Reduces friction and heat, preventing damage to the workpiece
- Carries away removed material, preventing the sandpaper from clogging
- Creating a smoother and more consistent finish
How to Wet Sand Metal
Tools and Materials You Need for Wet Sanding Metal
Before you begin, you’ll need to gather all of your tools:
- Wet Sanding Abrasives
- Most of the time you’ll use silicon carbide sandpaper. For specialized projects or to get larger projects done faster, there are other abrasive products capable of wet sanding metal like film PSA sanding discs, sanding belts, and non-woven abrasives. Just make sure that the abrasives you’re using are designed for wet sanding. We included a list of alternative wet sanding products at the end of this post.
- Grit Progression: You'll need multiple grits to gradually move up to finer grains for a smoother finish. The exact number of grits you’ll need will depend on the condition of the metal and your desired level of finish
- Lubricants
- Use clean water, mineral oil, or specialized sanding lubricants. Adding a small amount of mild detergent (like dish soap) to water can help reduce friction.
- Tools
- Sanding Blocks: Prevents uneven sanding and gouging by providing even pressure across flat surfaces.
- Sponge Pads: Provides flexibility for sanding curved or contoured surfaces.
- Power Sanders: These are useful for larger surfaces, but be aware that excessive pressure can lead to heat buildup and damage to the surface.
- Protective Gear & Cleanup
- Gloves, safety glasses, and rags/towels
Step-by-Step Instructions for Wet Sanding Metal
1. Pre-Soak Your Sandpaper
Before you jump in, its helpful to give your sandpaper a quick soak, about 5-15 minutes. Fully saturating your abrasives prevents them from gunking up on you later and makes it more flexible or any curved surfaces.
2. Clean/Prepare the Metal Surface
Next, make sure your metal surface is clean and ready to work on. Inspect the surface and dry sand any major imperfections or rough spots. When the surface looks ready, you’ll need to clean off any dirt, grease, or debris. A quick wipe-down with a degreaser or mild cleaner should work. It’s also helpful to tape off any areas you don’t want to sand (like edges or sections with a different finish).
3. Start Sanding with the Right Grit
If your metal surface is rough or has noticeable imperfections, you should start with a coarser grit, around 400. Use light, even pressure as you go. Pressing too hard can leave deep scratches that take longer to remove later.
For the sanding technique, use light even pressure to avoid gouging the metal or uneven sanding. Sand in straight overlapping motions. Alternate sanding directions each time you change the grit to get rid of visible scratches.
4. Grit Progressions
Work through the grits, progressing from 400 to 800 to 1200, and so on. You’ll know it’s time to switch when the previous grit’s scratches disappear.
- 400 Grit: Removes major scratches, imperfections, and oxidation
- 800 Grit: Removes finer scratches left by the 400 grit and prepares the surface for finer grits
- 1200 Grit: Removes even finer scratches and creates a smoother surface
- 2000 Grit: Produces a very smooth surface, almost mirror-like
- 2500 Grit and Above: Used for extremely fine finishes, often for show cars or high-end restorations
Remember: The number of grits and the starting grit you'll need will depend on the initial condition of the metal and the desired level of finish. For most projects, using grits from 400 to 2000 should be fine.
5. Apply and Maintain Lubrication
Wet sanding is all about lubrication. Keep your sandpaper and surface wet at all times. Soak the sandpaper in water or spray the workpiece with your lubrication of choice. This is important to prevent clogging and reducing friction that could cause damage or heat buildup.
6. Check Your Work Frequently
Don’t wait until the end to see how you’re doing. Every once in a while, stop sanding, wipe the surface clean, and inspect your progress. Look for scratches, uneven spots, or areas that need a little more attention.
7. Clean and Final Polish
When you’re happy with the look of your work, its time to move on from wet sanding to final polishing. To enhance the finish even further, polish the surface with a metal polishing compound and a buffing wheel or cloth.
About Wet Sanding Abrasives
Not all abrasive products can be used for wet sanding. You’ll need an abrasive that has waterproof backings and adhesives built into them. Silicon Carbide (SiC) is the most used abrasive grain for wet sanding, but there are specialty products made from other grains that work well in different scenarios. Always check with the product label and manufacturer to make sure the abrasives you are using are compatible with wet sanding.
Example Wet Sanding Products:
Silicon Carbide Wet Sandpaper Sheets
These 9” x 11” silicon carbide wet-dry sandpaper sheets are specifically designed for wet sanding applications. Silicon carbide grains provide superior cutting performance and durability, even when exposed to water. They are perfect for automotive refinishing, metal surface preparation, and fine finishing work. They can be used for manual hand sanding or wrapped around a sanding block.
Silicon carbide sanding belts combine flexibility and water resistance, making them suitable for metal finishing, deburring, and polishing applications. These belts excel in wet sanding due to their waterproof backing and abrasive grain structure, which prevents heat buildup. Use them on stationary or handheld belt sanders when working on curved or flat surfaces that require a consistent, professional finish.
Green Film PSA Wet/Dry Sanding Discs
These self-adhesive (PSA) green film discs are versatile for both wet and dry sanding. The flexible, waterproof backing makes them perfect for achieving a high-gloss finish on metal surfaces, especially in automotive refinishing or delicate metal polishing. The PSA adhesive ensures secure attachment to orbital sanders, while the film backing offers tear resistance and long-lasting performance.
Ceramic Sanding Belt for Wet Sanding
While ceramic abrasives are more commonly associated with aggressive material removal, these belts perform exceptionally well in wet sanding applications requiring durability and heat resistance. The ceramic grain maintains sharp cutting edges and reduces friction, preventing surface overheating. Ideal for metal fabricators working on stainless steel or harder metals that require extended sanding periods without compromising performance.
Hook and Loop Green Film Longboard Sandpaper
This green film longboard sandpaper roll is perfect for wet sanding large metal surfaces. The film backing resists tearing and ensures even material removal. Its hook and loop attachment system allows for quick grit changes, making it ideal for applications like automotive bodywork, metal panels, or furniture restoration.
These non-woven scuff pads are an excellent alternative to steel wool or traditional sandpaper for wet sanding, cleaning, and surface preparation. Made with durable, water-resistant nylon fibers impregnated with abrasive grains that won’t rust or shred during use. They are ideal for light sanding, rust removal, or blending finishes on metal surfaces. Perfect for hand use on intricate or curved surfaces where control and precision are required.