Priming the Repair Area – Why Prime and What Types of Primer to Use

It’s All About Cleanliness

If I can stress one thing throughout my training, that would be proper cleaning the surface be painted. The surface should be washed with dish soap and water before repairs begin. Then wipe the surface down with wax and grease remover. During repairs, use compressed air to keep the surface clean. Blow thoroughly before applying body filler or glaze putty. Then blow the repair area and wipe with wax and grease remover before masking. After masked wipe down with wax and grease remover once again to remove all finger prints. This sounds repetitive and it is. However, this will ensure proper adhesion and eliminate many problems during the painting process.

What Is Primer?

According to Wikipedia “primer is a preparatory coating put on materials before painting. Priming ensures better adhesion of paint to the surface, increases paint durability, and provides additional protection for the material being painted. The term primer comes from the Latin primus meaning first because it precedes the other coatings”

Adhesion Is Key, But There is More

Adhesion is a key reason to use primer. However, in automotive primers, it also provides corrosion protection too. Therefore, a primer that provide both good adhesion and corrosion protection is needed. I recommend to use an epoxy primer to provide these needs. Most epoxies can be applied on most types of substrates and is compatible with most top coats. Some technicians prefer etch primer to apply on bare metal to provide good adhesion. Etch primer has a high acid content that bites into the metal, but does not have the corrosion protection like epoxy does.

Mixing Epoxy – It’s Like The First Day Of Class

We use PPG products, but other brands may have similar directions. Be sure to read the manufacture procedure page to determine what they recommend. However, many epoxies have an induction time. This is a amount of time the two chemicals need to be mixed together before using. It’s like going to a new town or your first day of class. You’re quiet and nervous until you get to know the people around you. Once you get to know everyone, you feel much more comfortable. After mixing the catalyst with the epoxy primer, the chemical needs a little time to accept each other as well. It may only be 15 to 20 minutes, but be sure to read the procedure page to know for sure

Spraying The Primer

According to the new 6H rule, all primer needs to be sprayed inside an approve spray area. If you’re priming a small area, you may consider lowering the fluid, narrowing the fan pattern and turn the air pressure down. This will allow you to spray a smaller area with less over spray. Be certain to cover all areas that were sanded with 220 grit or courser. Apply two medium wet coats to the repair area. Remember not to spray primer all the way to your masking paper. Keeping the primer area as small as possible will provide the easiest repair.

Flash Time – Don’t Even Think About Passing Go

Flash time is the amount of time that is needed between coats. Rushing the flash time throughout the car paint jobs process is something I see often, which results in many different problems. Each coat must have time to flash to allow all of the solvents to evaporate. If you apply another coat before the primer has flashed off will trap the solvent and cause a number of problems. Loss of adhesion and solvent popping are a few of the most common problems. You must also realize that the time given in the procedure page are probably around 70 degrees. If it is 50 degrees in the shop at the time you spray the primer, then flash time must be extended. One coat at a time. No double coats or rushing the flash times. You’ve spent a lot of time on the repair, don’t blow it now.

Next, we’ll discuss primer surfacer.