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Covershield Primer OS – Penetrating Epoxy Oil Stop Primer Coating For Concrete Floors


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Location : Interior/Exterior
Task : Oil Stop Primer
Application : 3/8th Nap Roller
Surface : Concrete
Base : Solvent Based
Drytime : 3-12hrs
Coverage : 200 sq.ft/Gal.
Finish : Black

CoverShield Primer OS Solvent-Based Penetrating Epoxy Primer For Concrete Floors – Exclusively for Contractors

Oil Stop Primer

Primer OS is a solvent-based penetrating epoxy primer for concrete that exhibits excellent characteristics for coating over oil-soaked concrete.

Primer OS is recommended for petroleum oil contamination only.  This product  has been developed to block oil ‘bleed back’ from oil soaked concrete substrates and provide a primed surface for subsequent epoxy or polyurethane coating systems.

CoverShield Primer OS Oil Stop Primer

Primer OS is a solvent based penetrating epoxy primer that exhibits excellent characteristics for coating over oil soaked concrete.

Primer OS is recommended for petroleum oil contamination only.  This product  has been developed to block oil ‘bleed back’ from oil soaked concrete substrates and provide a primed surface for subsequent epoxy or polyurethane coating systems.

Why Use A Product Like CoverShield Primer OS?

If you’re an architect, environmental engineer, contractor or property developer that has the problem of oil in a concrete slab, and you’re worried about the oil coming back up and causing delamination of the flooring system that you want to use, we have a solution for you.

Whether you’re using an epoxy coating, a vinyl wood floor or some type of cement overlay, we have a primer OS product that’s an oil stop primer.

It’s developed specifically to soak into the concrete slab, fuse with the oil, and prevent it from bleeding back up onto the surface.

Since it’s a primer, you can then apply your epoxy coating or other flooring system on top of it afterwards. So, it’s a very effective way of dealing with what we call oil bleed-back.

It also avoids the costly process of removing concrete if it sustains heavy oil staining. This is a much more cost-effective way of dealing with this problem.

Do You Really Need A Primer When Using An Epoxy?

It really depends on the type of floor that you have (the concrete floor or surface) and the type of epoxy you plan on using.

You should prime a surface generally for three reasons:

  1. To improve the adhesion
  2. To stop out-gassing of air and vapor coming up through the concrete
  3. To increase durability. (To put a thicker, more durable surface or system onto the floor.)

If you have an epoxy that is very thick, you should use a primer first to get better adhesion.
The primer will soak in, and let the thicker epoxy sit on top of the floor.
If you have contamination in the slab – something like oil – then you should prime to prevent that oil from bleeding back and delaminating the epoxy topcoat.

What Is CoverShield Primer OS?

CoverShield Primer OS is an oil-stop primer developed specifically for stopping oil bleeding back to the surface of concrete.

It’s used on oil contaminated concrete surfaces where you want to coat that floor with an epoxy, or some kind of cementitious or vinyl or wood flooring system. However, you’re worried about that oil bleeding back and causing delamination afterward.

Examples of such areas include:

  • An industrial facility
  • A chemical factory
  • An automotive workshop
  • A warehouse.

Primer OS was developed specifically to block the oil coming up to the surface.
It is a penetrating primer. It has petroleum compounds that fuse with the oil and block it from coming to the surface.

At the same time, it provides a primed surface which you can then coat with an epoxy, a flooring adhesive, or a cementitious overlay – without having to worry about any oil bleeding back.
It’s a very cost-effective way of dealing with oil bleed-back and avoiding the huge expense of ripping out a contaminated slab.

Why Is CoverShield Primer OS Better Than Retail-Store Brand Epoxy Primers?

CoverShield Primer OS is better than regular primers you will find in a retail or big box store.

These off-the-shelf products are not developed or designed specifically to deal with an oil contaminated surface.

Those primers will say specifically that oil cannot be present. So, you’re unlikely to find an oil stop primer in a retail store.

Oil stop primers need to be developed specifically with compounds that are compatible with oil.
As such, they will fuse with those oil hydrocarbons to stop them from bleeding back to the surface.

How Do Typical Epoxy Primers Work?

Primers are typically a thinner, low viscosity type of material that soaks into the concrete surface, wets it, fills up any pores, and provides you a better surface to bond to. You’ll get better adhesion with your epoxy topcoat or your adhesive.

Since the primer penetrates into the surface, it is going to make it harder and stronger. It’s also going to prevent contaminants, chemicals and moisture from coming up from underneath.

CoverTec has an oil stop primer that will stop oil coming up. We also have a water stop primer that’ll stop water and vapor coming up through the floor. At the same time these primers harden the surface and provide a good surface for a topcoat to bond with.

What Are The Benefits Of Using CoverShield Primer OS Over A Store-Bought, Competing Product?

CoverShield Primer OS is an oil stop primer. It’s developed specifically for stopping from oil bleeding back to the surface of a concrete surface.

So if you have an oil contaminated slab, and you’re planning to add a topcoat, an epoxy, some kind of cementitious overlay, rubber or wooden flooring, then you’ve got to consider that the oil could come back to the surface and cause peeling and delamination.

Most primers won’t address that problem. They can’t handle the oil coming back up to the surface, whereas CoverShield Primer OS is developed specifically to prevent that from happening.

It will penetrate into the surface, fuse with any petroleum-based oil, and provide a barrier to prevent what we call oil bleed-back.

What Are The Do’s And Don’ts When Applying CoverShield Primer OS?

This is a primer developed to penetrate into the surface of the concrete and provide a barrier to oil bleeding back up. So, it’s important to make sure that the surface is as clean as possible. This makes it easy for the primer penetrate the concrete.

We recommend you use something like our CoverClean HC. It’s a cleaner developed specifically for removing petroleum-based oils from the surface and sub-surface. It’s a microbial cleaner, and it’s very effective.

It’s not a good idea to grind or shock blast the concrete. That’s definitely a DON’T because it’s going to drive the oil deeper into the slab. You don’t want to generate heat.

The product should be applied using a 3/8th nap roller, or it can be applied with a sprayer.
It contains some solvents, so make sure the area you are priming is well vented to allow the odors to dissipate easily and quickly.

CoverShield Primer OS dries very quickly. Typically, within 4 to 5 hours. You can add a topcoat or re-coat the surface on the same day.

The recommended temperature for applying this product is between 40 and 90 degrees. We don’t recommend applying this product when it’s too hot or cold.

Why Is CoverShield Primer OS Recommended For Use By Contractors Only?

This product is a professional-use product. The surface needs to be cleaned in a specific way before applying the primer. The primer has some solvent to it, so you need to be trained how to handle it.

And it really is designed for industrial or commercial use, where you’re trying to protect the concrete slab from oil coming back up and causing delamination.

What To Consider (Or Look For) When Selecting An Epoxy Primer?

You should look for something that is a low viscosity epoxy primer. One that is thin and will penetrate deep into the concrete, providing what we call “maximum wetting out of the surface”.

If you’re dealing with moisture problems or oil issues, make sure the primer will resist moisture, vapor or oil from coming back up to the surface.

Make sure it’s compatible with the topcoat you plan to use. If you’re using a water-based topcoat or system, the primer and the topcoat should both be water-based so one doesn’t damage the other.
Read the product label or speak with your product provider regarding any restrictions on the product. Things like:

  • Specific steps on handling the product
  • Whether there are any solvents
  • If there are any safety issues you should know about
  • Etc.

These are the key things you need to know.


  • Barrier against oil
  • Stops oil “bleed back”
  • Compatible with a wide range of coating systems
  • Can be top coated same day
  • Resists petroleum based oil
  • Chemical resistant

Main Uses

  • Floors
  • Pump pads
  • Trenches
  • Sumps
  • Drains

Surface Preparation

The substrate must be structurally sound. Loose or unsound concrete should be removed and made good. Surfaces must be entirely free of oil, grease, paint, corrosion deposits, dust, laitance or other surface deposits. Any cracks or pock marks should be filled with CoverBond PF160 before application of Primer OS.

Cleaning Oil Contaminated Slabs

Clean the slab using CoverClean HC. Wet the floor by misting the surface with water and then immediately apply the CoverClean HC. The cleaner may be applied by either a pump up sprayer spray or medium bristle brush at a rate of 200 to 250ft² per gallon (4.9 to 6.1 m2/L). For heavy duty cleaning apply at a rate of 150 to 200ft² per gallon (3.7 to 4.9 m2/L).

The affected area must be agitated with a stiff brush. This can be manual or with a power scrubber depending on the size of the area being cleaned. The solution temperature must not be allowed to rise above 120°F (48.9°C) or to completely dry out. Water must be present at all times, since this is the source of oxygen for the microbes.

Allow the CoverClean HC to sit for a minimum of 3 hours

Keep wet during this time and agitate one more time, 20 minutes before rinse off. If the product cannot be rinsed to a drain, then use an auto scrubber or similar to wet vac up the liquid.

Allow substrate to dry before applying Primer OS


Mix Ratio 1:1 by volume.

Condition the material so it is at a minimum temperature of 60°F.  Add 1 Part B in to 1 Part A and mix using a slow speed drill and paddle for 4 minutes until both components have fully dispersed and are uniform in color.  Be sure to rotate the mixer throughout the pail.


Make certain that the floor temperature and air temperature is between 60 and 90°F.  Apply product by 3/8th solvent resistant non shedding roller or brush at 200 ft2/gal (8 mil thickness when wet).  Too thick of an application may result in product failure.

Top coat or recoat

Primer OS can be top coated with epoxy and /or urethane systems  within the recoat window (3 to 12 hours at 77°F). We recommend 1 coat of Primer HS and 2 coats of CoverShield U270 (see separate data sheets and color chart for color options). If different topcoats are desired, contact CoverTec for application details before proceeding. Proposed intermediate and topcoat selections should be evaluated for adhesion and compatibility.  A representative sample patch should be applied for this purpose.

This product is exclusively for contractors.

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