You should not confuse MDF as solid wood. While wood IS a material used to make MDF, there is a reason it is called ‘wood product.’
The full form of the term MDF is Medium Density Fiberboard. Instead of throwing away the leftovers from wood craftings, such as woodchips, and other small wood particles, they are taken to the factory and broken into small particles.
After that, those particles are mixed up with resins and waxes. The mixture is then pressed in high heat to form solid boards named MDF, an alternative to wood planks.
Necessary pieces of equipment
You should seal and, if necessary, paint MDF for your workbench before use. Luckily, sealing the MDF workbench top is a pretty undemanding process and does not need complicated types of equipment. Usually, you can get them quickly.
A face mask
An MDF-suitable sealing agent
Oil paint (If you want to paint it)
What Can You Use As Sealer?
MDF is highly water absorbent. That is why not all kinds of primers or paints can be used to coat its surface. When you go to buy materials to seal your MDF workbench top with, try to get one compatible with it.
Here is a list of sealing agents that you can use to seal your MDF.
Oil-based filling primer- Shellac (A mixture of paint and sealer), Polyurethane
Drywell compound and primer
How to Seal MDF Workbench Top – 5 Steps with Tips:
If you want your MDF workbench top to last for long, you must thoroughly seal it against water. For that, you must know how to finish the MDF workbench top well.
Fear not. Sealing MDF is an easy procedure. Our step by step tutorial is here to help you finish your goal with ease. Just clear your mind from worries and follow the guidelines carefully.
Before you get too hyped up, remember to take safety precautions and prepare yourself. After all, fumes originated from primers, and paints can be harmful to your body.
So remember to wear an overall, gloves, eye protection, and a mask before you start working.
The first sanding 
Sealing MDF requires it to be sanded several times. If you think of giving an MDF a sanding before starting sealing is too much, you can skip this stage.
But if you want your workbench top to look good and last longer, we suggest you lightly sand it down before you begin working with the sealing.
Lightly sand it using sandpaper. Make sure to give the edges a little bit of extra attention. And after you are done, carefully clean up the dust particles thoroughly. Read Also: How to Sand Plywood to Get a Smooth Finish
The sealing begins with the edges. 
Now that you are ready, let us begin with the sealing. Don’t start with the surface yet, start with the edges first.
The edges of MDF are the most water absorbent. So make sure that you coat and seal them well.
You can use an oil-based filling primer or PVA glue to seal the edges of your MDF workspace. Instead of them, you also can use drywall compound and primer.
Using an oil-based filling primer or PVA glue 
The methods for using primer and PVA glue are the same. Use a synthetic brush or a sprayer to coat the surface of the edges evenly. Wait for the coating to dry.
After drying, lightly sand it down, but be careful not to sand down the coating itself. After all, all will be in vain then.
After you are done with the sanding, recoat the edges with the primer or glue again and follow the previous procedure.
It is best if you follow the same procedures several times and give you MDF several coatings. That will make your MDF both sturdy and humidity resistant.
Using Drywall Compound and Primer 
Another way of sealing the edges of the top of your MDF workbench is to use a drywall compound and then a primer to coat it. The process is similar but more prolonged.
If you wish to use this method, you should first use a drywall compound to apply an even coating on the edges’ surface. When the coating is dry, you should sand it down.
After your sanding is done with, you can then use a primer to recoat the drywall coating. Again wait for the primer to dry to give the coat another sanding.
Continue following these steps for two to three times. Read Also: How to Sand Table Legs -In 7 Effective Ways [Like a Pro]
Sealing the surface 
Sealing the surface of your PVA workbench top follows the same procedures required to seal the edges. What makes sealing the surface different is that you can use more types of materials like enamel primer and lacquer primer to seal the surface.
Otherwise, the whole procedure is precisely like sealing the edges. Coat it and then sand it, and replay the process several times and be done!
See? A pretty simple process.
Things to Keep In Mind
While working on MDF sealing is a simple process, some wrong steps can complicate, and even spoil the whole project. So, make sure you remember the following advice while working on your MDF workbench top.
Remember to avoid water-based glues or the glues that require water for use. Instead, use acid-neutral ones.
Multi-purpose primers can be tricky. So try to avoid using a versatile primer.
Use a high-quality synthetic paintbrush, or a roller, or a spray bottle.
Make the coats as thin as possible if you use enamel primer and make sure to choose a colour that will go well with your final color.
If you opt to use lacquer primer, remember to test if it goes well with your paint or not.
Keep these bits of advice on your mind while you seal your MDF workbench top to avoid facing any complications.
MDF is quite useful as a workbench top. Many feel unsure of using it because it tends to warp in contact with water. But as you can see, you can solve this issue quickly. So, keep in mind how to seal the MDF workplace top, follow the steps well, and save your money.
Hi, I am Rogers Weber, the man behind Solvesonic. I am a mechanical engineer. I use many kinds of tools almost every day at my workplace. I love to write about tools, painting, home improvement, and DIYs. I enjoy helping people to solve their problems through my website. => Follow me on Twitter