You have to not only read the P-sheets carefully, but also make sure that what you're reading is the "Official" p-sheet for the product.
For the 225, this is the p-sheet:
http://www.performancecoating.dupont.com/dpc/en/us/html/prodinfo/chromasystem/H-19290_225S.pdf
For the 226, this is the p-sheet:
http://www.performancecoating.dupon...prodinfo/chromasystemlv/H-19393_226S_Alum.pdf
For Variprime, this is the p-sheet:
http://www.performancecoating.dupont.com/dpc/en/us/html/prodinfo/chromasystem/H-19303_615S.pdf
Maybe I didn't read close enough, but I couldn't find any mention of where Variprime is "recommended" for use directly over either the 225 or 226 treatment. (Logically, however, and in my mind, I don't see why using Variprime over JUST the 225 "etching" chemical would hurt anything, but I sure wouldn't use it over the 226; that might cause problems. Still, I wouldn't do EITHER, and for no other reason than that Dupont didn't say that I could
)
The only "substrate" shown and approved under the Variprime in the Variprime p-sheet is:
"
Substrates: Properly prepared/cleaned steel, aluminum and galvanized."
Without going any further, I personally take that to mean "bare metal" that has been cleaned of contaminants. However, for further clarification as to what specifically means "proper preparation", the very next paragraph in the p-sheet says:
"
Surface Preparation
Wipe surface with DuPont First Klean 3900S™ or Prep-Sol® 3919S™.
Sand and featheredge with P180 DA grit paper followed by P240 DA grit.
Remove sanding residue with DuPont 3939S™ Lacquer and Enamel Cleaner, DuPont Final Klean 3901S™ or DuPont Kwik Clean 3949S™."
All of those are just degreaser chemicals and sanding... no metal pre-treatment at all.
Please don't think I'm trying to start a p****** match with what might seem to be nitpicky details. It's just that I've been bitten hard by overlooking teeny little details in how products work together and I'm hoping to let my mistakes, oops, I mean "experience" help others.
Will doing what you are result in paint peeling off in sheets a few months after it's painting?... I don't know; probably not.
But you might find that adhesion might suffer a little from spraying the Variprime over the 226, and it might appear that leading edge surfaces will chip a bit more easily that you would like (from thrown up rocks and sand abrasion).
There's enough that can go wrong in the paint process when you do things exactly right without pushing one's luck by going outside the intended use of manufacturers products.
Speaking of going wrong when you do things right, and as an example... I have a vivid recollection of a Corvette I painted years ago where some of the paint prep was done about 50 feet away from where a car was being detailed for delivery to a customer.
No one noticed the newly hired helper grab a bottle of ArmorAll and spray it quite liberally over the tires on the car he was cleaning. I won't go into the gory details of how spray silicon that drifts onto a car (yes, 50 feet away!) just before painting makes things really interesting.
Let's just say it ain't pretty.
Thanks for bringing up yet another memory that makes me happy that I'm doing something else for a living now.
Highflight
RV7-A