How to Sand Metal Smooth for Painting – Shiny Bathroom

Even though metal is a fundamental element in the construction aspect, it’s vulnerable to rust.

They are imminent to expire after a certain period of time. Moreover, even stainless steel is susceptible to losing its shininess. Luckily, you can restore the smoothness and shininess by sanding the metal.

In this article, I will guide you through how to sand metal smooth perfectly. With both the intention of paint perpetration or recovering the glittering ancient looks. This guide will help you thoroughly and you’ll come out a PRO in sanding metals.

It’s worth noting!

Sanding metal helps to get rid of unwanted and old colors. It’s also essential when you’re about to apply metal glue prior to joining two pieces. In addition, it helps to eliminate any scratches or rust. Hence, the surface becomes even and brought back the smooth ancient look.

Sit back and keep scrolling!

Let’s first get started with some important key pointers for choosing the appropriate sandpaper for sanding metals. Cause I believe that’s the most critical first step with no room for mistake.


Metal sandpaper type and grit

There are various sandpaper grit types as well as grade impacts. Therefore, it’s good to be familiar with the various types and grits of sandpaper. This will help you to always choose the appropriate one when sanding metal.

But, why does this matter?

Firstly, different sandpaper grits are intended to perform extremely different jobs. Secondly, choosing the right grit for a certain task can be very confusing when you are just starting out.

It’s worth noting that sandpaper is not made up of sand. Instead, it has fine particles that are either obtained from synthetic or natural sources. These particles are the ones known as grit or grains. They’re sifted by screens and then sorted by sizes.

After they’re sorted, the particles are bonded with an adhesive to a cloth-type, sponge, or paper backing. This results in an abrasive material (sandpaper) which is useful in various situations such as sanding metal.


Sandpaper grit chart for Metal

So, what is the best grit for sanding metal?

As I previously stated, distinguishing the sizes of sandpaper grit is important. It’s because all projects don’t require the same. For instance, extremely coarse grits can be used to quickly remove a lot of rusty material from the metal surface.

On the other hand, finer grits have the ability to produce a mirror finish.

In the USA, the determination of grit is based on the gradation scale that was established by CAMI (Coated Abrasive Manufacture Institute). The measurement of grit on a CAMI scale is done in microns. When you’re buying sandpaper, you will see numbers like 200-grit, 100-grit or 80-grit.


And how do you determine the best grit? Well, here’s the deal;

The higher the number on the sandpaper, the finer and smaller the particles. Moreover, the surface finish you’ll achieve with this type of grit will also be finer. Conversely, the lower the number, the larger the grains as well as overall coarseness of the sandpaper.

What do I mean?

If you look at 100-grit sandpaper, you’ll realize that its grains are larger than the ones on 200-grit sandpaper. Most sandpapers in the market today bear the CAMI scale.

However, you might also come across sandpaper grits that are sized by FEPA (Federation of European Producer of Abrasives). Grits sized using the FEPA scale are indicated with the letter ‘P’ appearing before the grit size.

There are too many gradations of grit to list. However, when purchasing sandpapers, the CAMI sizes below will help you determine the one that closely corresponds to FEPA sizes.

  • 400-grit sandpaper (CAMI) closely corresponds to P-600/ P-800 (FEPA)
  • 220-grit sandpaper (CAMI) closely corresponds to P-180/ P-220 (FEPA)
  • 120-grit sandpaper (CAMI) closely corresponds to P-120/ P-150 (FEPA)
  • 100-grit sandpaper (CAMI) closely corresponds to P-100/ P-150 (FEPA)
  • 80-grit sandpaper (CAMI) closely corresponds to P-80/ P-100 (FEPA)
  • 40-grit sandpaper (CAMI) closely corresponds to P36/ P-40 (FEPA)

So, that’s the maximum of 400 girts that we talked about. But girts are available up-to around 10,000 based on different purposes. Now, let’s talk about different kinds of metal sanding methods.


Different methods of sanding metal

One of the most common methods of sanding metal is using sandpapers either manually or with a sanding machine. Alternatively, you can use sanding blocks. Let’s have a look around at each of these methods and determine how effective they’re.

1. Sanding with sander machine:

An orbital machine is the most commonly used sanding machine. This is mainly due to the fact that they do hard work easily and very quickly. Moreover, orbital sanders provide outstanding results, particularly on extensive surfaces or large ridges. They are also quite affordable and durable. However, if there are some tight spaces where paint, ridges, or rust remains, you can use the second method, which is using hands.

2. Using hands:

This process involves using the sandpaper sheets manually to remove rust, paint, or ridges from the surface. The process is very effective, especially in the right places. When you’re using hands, the best way involves sanding along the metal grains. However, you can also sand in circular motions. Once you’re done removing most of the undesirable material, switch to the 200-grit sandpaper. This will help you to finish off the process appropriately.

3. Sanding without sandpaper:

So how do you sand metal without sandpaper? Is that even possible?

Yes, as mentioned earlier, you can also sand metals using sanding blocks instead of sandpapers. Sanding blocks also tend to do that effectively. However, they require more time and physical effort to complete large surfaces than sanding machines. Moreover, it is difficult to guarantee clean, smooth and scratch-free outcomes.


How to Sand Metal Smooth for Painting

Having the skill of sanding can be very useful in various circumstances. For instance, you might need to remove old paint or even out the scratched parts of the metal surface. Similarly, you might want to prepare for painting as well as other treatments that require proper preparation.

Thorough sessions of sanding results to even and smooth surfaces across the metal. They also leave it ready for various purposes like painting or high polishing. And when you want to get rid of big pieces of material, it’s better to grind before you sand.

Without wasting any time, let’s dive right in and see how to get this done.

1. Sanding metal surfaces for painting

Before you apply paint on metal, ensure that you’ve prepared the surfaces until it’s rust-free and clean. If you have old paint that needs refinishing, then first sand paint off the surface. Once the paint is gone, remove the deviated dust particles and the surfaces should appear dull instead of shiny.

It’s important because that ensures durable paint adhesion on the metal. In order to accomplish that, you should follow the following processes step-by-step:

  • Cleaning & Rust Removal: Use a degreasing agent like tri-sodium phosphate to wash the surface of the metal thoroughly. Then rinse and leave it to dry. Examine the surface for any rusty area and use the appropriate tools to remove all rust. For instance, you can use steel wool or 80-grit sandpaper for small areas and light rust. On the other hand, you can use a wire brush and a scraper for a moderate amount of rust. Similarly, utilize a drill with a wire wheel brush for extensive rust and finish with sandpaper.
  • Sanding & priming: Once you’ve removed the rust, sand the entire metal surface until the uneven areas are smooth and dull. This will help the paint and primer to stick on the surface. Begin with the 120-grit sandpaper, then continue working to finer grit sandpapers and end with the 320-grit sandpaper. However, for flat and large surfaces, use sanding blocks to get uniform pressure. After sanding, remove the dust by wiping the entire surface using a tack cloth and instantly apply the first primer coat.  You either apply primers with a spray can, paintbrush or a roller. Apply 2 primer coats so as to get the best results. During application, let the first coat dry and then sand lightly before you apply the second coat.

However, before you start this process, go through the label on every product. This will help you to ensure they’re suitable and compatible with the type. Moreover, adhere to the safety procedures of the manufacturers.


2. Wet sanding metal

Wet sanding is mainly used in auto paint, glass as well as metal applications. It’s usually the best method of eliminating minor defects caused by scratching. Moreover, it’s a great means of refinishing dull surfaces to a high sheen.

Although wet metal sanding isn’t a difficult task, the process requires a watchful eye and patience to ascertain job completion. Additionally, it needs little preparation and uses a few readily available and affordable items.

But the question is: How can you use this? If you’re asking the same question too, relax and let me guide you through the entire process step-by-step.

  • Step 1: Spray water and wipe down the surface that will be sanded. Then spray metal degrease and wipe using a rag. However, ensure that the rag to be used is clean. Repeat the entire process once again but remember to use another clean rag to wipe the surface.
  • Step 2: Fix 180-grit sandpaper that is specifically designed for wet sanding to the sanding machine.  Fill water in a small bucket and dip the fixed sandpaper in the bucket. Never dunk the sanding machine in the water under any circumstance since it may cause electric shock. Therefore, you should only wet sandpaper.
  • Step 3: Spray water in the area that will be sanded thoroughly and then sand the metal surface in a steady and slow motion.
  • Step 4: Repeat the first step. That means, spray water on the surface and wipe using a rag. Then spray again with a metal degreaser and wipe with a rag.
  • Step 5: When you’re done with wiping the surface, replace 180-grit sandpaper with the 320-grit paper. Then repeat step 2, remembering to maintain the same steady and slow motion. In addition, add water to the surface and never let it go dry.
  • Step 6: After you complete step 5, repeat steps 1, 2, and 3, but only after replacing the 320 grit paper with 460-grit sandpaper. Then repeat the same steps with the 600-grit sandpaper and lastly clean the surface with a metal degreaser.


3. Using wet dry sandpaper on metal

Wet and dry sandpapers refer to sandpapers that have a waterproof backing and adhesive as well as silicon carbide grit. They are also known as silicon carbide sandpapers or waterproof sandpapers since they have a waterproof backing and a resin bond.

In addition, wet & dry sandpapers tend to be more effective when used wet. This is mainly due to the fact that the grit being washed away from the surface reduces clogging. Moreover, they also have some benefits because of cooling and lubrication.

Wet & dry sandpapers are available in various grit sizes up to 10,000. For general metal finishing, use the wet 40-600 grit and above 1000-grit to cut back between the coats of spray paint. One great thing with wet & dry sandpapers wet is that it prolongs its service life and produces better finishes.

Moreover, adding washing liquid into the water being used helps to lubricate the sandpaper.

Apart from metal, silicon carbide sandpaper can be used as plastic and wood sandpaper. It does various tasks such as rust or paint removal, sanding between coats as well as rough sanding.


4. belt sanding metal

Sanding metals using a belt sander is a quite quick process. Belt sanders are multi-function tools and require sanding belts to use. They can cover a large area in a short period of time. So, they save time and effort. But it might a bit difficult for novices to use a belt sander for the very first time.

With a belt sander, you must ensure that the right sanding belt has been selected. And then while applying, the right motion and direction ratio should be maintained in order to achieve the expected smooth surface. Hence you should be familiar with the tool as per the weight and functions.

It’s always good to start with the coarse hard disk when you’re using the orbital machine. For instance, the 80-grit disk is fairly coarse. And conveniently removes the top layers of rust, paint, or scratches from the surface. But there is a catch! Always sand slowly and carefully when you’re using the coarse sanding disks. This helps to avoid weakening the metal by eating into its surface. Thus you can sand the paint off. Once you’ve removed the top layers of material or old paint, switch to a finer and higher grit.

You should consider finishing sanding the metal off with the 200-grit disk since it is smoother. Additionally, this disc doesn’t eat into the surface. This enables you to give metals a great sanding till the surface is clean and nice.

Also, it is recommended to put some extra padding on the edges of the sanding materials. So the sanding belt doesn’t hurt the edge brink directly. Then once sanding is done, you can measure the right size you need and cut off the extra padding.


5. Sanding metal with angle grinder

Using flap sanding discs you can sand metal with the help of an angle grinder. Like the electric belt sander machines, this is another powerful electric tool that can be used for sanding with ease. This is a cost-saving option to cover a large area effectively.

First, select the right sandpaper that meets your expected and finishing capability. Note that flap overlapping sanding discs are very powerful with angle grinders.

Then all you need is to stroke the grinder gently on the material. Be soft handed but not careless. Thus you can handle the grinder on the surface with the right motion and angle. With the powerful rotating motor, it finishes the surface like a charm. You can either use pieces from coarse or fine sandpapers so as to remove any material left in tight places. Lastly, finish off the process using steel wool in case you want the finish to be smoother.



Quality sanding offers new life to various metal surfaces. Therefore, knowing how you can sand metal efficiently will be useful during renovations. Moreover, it is an important skill in several tasks and professions. The content of this article contains all the necessary information on metal sanding. And if you have gone through it well, hopefully, you’re one step closer to achieving great results.

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