.This is a video response about primers. There are so many different primers, how do you know which one to use for your car? I’ll do my best to explain it in this video.
Bare Metal
- Self Etch Primer (acid) or
- Epoxy Primer
Filling Scratches, Body Work, etc.
- Primer Surfacer aka Primer Filler or Fill Primer must be sanded
Alternative Option
Direct To Metal Primer (corrosion protection + filling) must be sanded
Color Hiding
- Primer Sealer (not required, but helps hide and cover color variations)
There are other primers and systems out there, such as tinted primers, UV primers, but this may become confusing if you are not familiar with them, so we’ll keep it to the basics. However, I do recommend all 2k (two-part) primers, except for the etch primer which is a 1k primer. 2k simply means the primer mixes with a catalyst making it a two-part.
In response to This is in response to https://www.youtube.com/watch?v=Y_SJSyExkJI
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Good job on explaining the difference between the coating of bare metal with either epoxy or self-etch (acid) primer. The main reason as to why polyester filler doesn’t work over a self-etch primer is because the acid inhibits the curing process of the polyester resin. Additionally, polyester fillers can swell and soften the self-etch primers since these are single component or un-catalyzed coatings. Generally speaking it is safer to recommend using 2 component products with 2 component primers, and use single component products with single component primers.
If a self-etch primer was used for corrosion protection for bare metal, apply a 2K primer (2 component catalyzed primer; in most cases urethane) over the self-etch before applying a filler. In this way the 2K primer will act as a barrier coat to keep the self-etch primer and filler from coming into contact with each other. Or to avoid any issues just use an epoxy and eliminate the concern. Several restoration shops use epoxy primers for long term storage or extended restoration projects because of their corrosion resistance and because fillers can be used directly over them.
Another option as primer surfacer (filler) is a polyester primer because it offers high build with minimal shrinkage over time. In some cases where a high build urethane primer is over-applied to “hide” or correct surface defects, those defects are only hidden for a period of time. These chemistries have the potential to shrink down over time and allow the area to show up in the finished paint as a “mapping” issue where the repair area can be seen under or through the paint.
Hopefully this will help your viewers in their selection of primers for their projects.
Hi Tim, thanks for your comment and expertise on the topic. Yes, I find this very helpful.