How to use UreChem OxyStick EP-21 Epoxy primer

OxyStik EP-21 Auto Primer

Today's topic is the proper use and application of our 2k epoxy primer OxyStik EP-21. Two-component or 2k epoxy primers such as OxyStik epoxy primer, offer best-in-class adhesion and corrosion resistance to a wide range of surfaces including bare metal, fiberglass, gel coat body filler, existing paint finishes, and even many plastics used in the automotive industry.

OxyStik EP-21 is currently available in gray and we will also be adding white and black in the near future. OxyStik EP-21 is for use only in areas that do not require Low VOC products most of the united states does not require a low VOC product but some areas do such as most of California, Maryland, Delaware, and potentially other areas as regulations evolve. Always check local regulations before purchasing.


Before you start mixing and painting, make sure your parts have been sanded and cleaned properly and conditions are good for painting.

To properly prepare your bare metal parts for paint, use UreChem’s SBWG Wax and Grease Remover and dry sand with any 1 grit in the P80 to P220 range followed by cleaning again with SBWG.

All other surfaces should be cleaned with SBWG sanded with anyone grit in the p220 to p400 range and cleaned again with SBWG. for more details on the proper use of surface cleaners refers to our video tech sheet for surface cleaners on our website.

As with any automotive finish, proper painting conditions are important for obtaining the best results. Epoxy primers tend to be less tolerant of cold conditions and OxyStik EP-21 should not be used if your part material or shop temperature is less than 60 degrees Fahrenheit.

Keep in mind that the conditions outside are brought into your paint booth through your booth intake. Moisture should be a concern when applying automotive finishes, so unless your paint booth has the ability to heat your parts well above the dew point, you should not paint when it is raining, dew on the ground, or fog in the air.

Parts painted at temperatures near the dew point can easily condensate thin layers of moisture which are often not visible on the surface or in the paint film itself but can cause failure of the finish so it's best to wait until you can paint in proper conditions. Remember, air temperature does not directly correlate to the surface temperature of your project.

Safety & Mixing Procedures

Once you have your parts properly prepared and the conditions are good for painting, start by wearing the appropriate personal protective equipment and only use this product in areas that are free of ignition sources such as heat, sparks, or open flames.

OxyStik EP-21 mixes in 1:1 by volume with EPA activator. UreChem branded mixing cups have a column specifically for a 1:1 mix ratio. Simply pour the desired amount of primer to the number in the 1:1column you select based on how much material you need, then add EPA activator slowly on top of that to the corresponding number working left to right in the column.

So if you fill primer to the number 3, you will fill the EPA to the number 3 and the row immediately to the right. The numbers in the mixing column do not relate to volume, they are simply referencing points. For more information on paint mixing cups, refer to our video on how to use UreChem paint cups. An additional 10% UreChem urethane reducer can be added if you would like. Once you have added the primer and activator mix well with a paint stick scraping the sides and bottom of the cup occasionally will ensure all the materials are thoroughly mixed.

Spray Gun Configurations

Once you have a good spray pattern, spray your test panel to make sure the product flows well and you're happy with your settings. Apply two to four medium wet coats with 50 to 75 overlap. Over-application of base coat is a common error so be sure to avoid applying wet or shiny coats. A 6 to 8-inch fan pattern and approximately a 6-inch standoff or distance from the surface is a good general rule. 

For harder to spray metallics and pearl colors, a 75 overlap followed with a drop or mist coat for your final coat will help ensure an even appearance. For more on this subject, look for our video on spray practices for applying effect finishes. 

Spraying A Test Panel

Test spray and check your pattern. Your spray pattern should be a tight and uniform ellipse shape once you have a good spray pattern spray a test panel to make sure the product flows well and you're happy with your settings.

Now apply two to three medium wet to wet coats with fifty percent overlap a 6 to 8-inch fan pattern at approximately 6-inch standoff distance from the surface is a general recommendation. Be sure to allow fifteen minutes flash times between each coat to avoid solvent entrapment. After your last coat, clean your gun immediately with a suitable cleaning solvent, lacquer thinner, acetone, or MEK. Check local regulations for compliant gun cleaner options.

Flash Times & Spray Gun Cleaning

OxyStik EP-21 requires two hours at 75 degrees Fahrenheit cure time before top coating and may be top coated without sanding for up to 48 hours. Wait at least 24 hours before adding any body filler product over OxyStik primer then sand and clean with SBWG.

Be sure to check out the Tutorial video below!