I keep reading about people using primers for exposed parts like the wheel wells.   Primers are by definition very porous.  They are designed to absorb surface coatings and have a high surface energy (which is the opposite of waxing with low surface energies) as a way of promoting bonding.  In addition, the epoxy backbone is sensitive to UV light and has the bonds broken at that frequency and energy, (acrylic polymers are not very sensitive to UV frequency and thus are long lasting in sun).  Why not use a urethane?  It will not stain or discolor as easily as epoxy based primers.  True, the primers tend not to run as easily and are easier to apply than a gloss.  And a gloss will not hide flaws very well but I'm sure all of the work out there is flawless!

 

So why use a primer?  What am I missing?

 

Dan Newland