Hot Rods Black ecoat - sand it before primer?

You should always do the thinner on a rag test. We have always stripped the panels down all the way with #80 grit for restoration parts and pcs regardless. Unless you know the car or parts have been sent to an actual reputable coater like listed above. Found rust under the E-coat more than once and the other part of the time they will have adhesion problems . The general rule on newer car-daily driver stuff was always scuff/sand primer when needed on to paint if it past the thinner test.

 

Well, sorry to disturb any sensitivities but I'll stand by what I said.

And well wouldn't ya know that the very car that sodomized itself for me was also a Speed33. E-coat was sanded beyond thorough and it proved to be an awesome release agent for 2K primer. Peeled off like aunt Nellie's old shelf paper in the cupboards. Anyone's welcome to say "...and you probably..." or "...you shoulda..." but save your breath (fingers?). You could see the inverted pattern of sand scratches on the back of the primer that peeled yet the remaining coating on the sheetmetal was undisturbed. Everywhere I went through the Ecoat to bare metal was stuck good. Never again. Unless it's actual epoxy that I applied I want nothing to do with it. And I think I've established over time that I'm on at least my 2nd rodeo when it comes to refinishing.

Now I'm not sure if that was polite or not but in true hoodlum fashion I guess I also don't care. Today this work is expensive beyond our wildest thoughts and now materials are more expensive than the vig from a loan shark. For record I happily take the title as the "one" in this crowd. Please note that in the interest of maintaining proper etiquette I had a pinky raised as I bumped this out. My polite dept is fairly low on inventory so that's the best I got.

 

Yah, but Highlander; your avatar has four raised... . Hope you get better soon. .
Marcus...

 

Block sanding to find any defects to fill.... should that be before or after epoxy primer?

 

I tend to ruffle the occasional feather on this question. I won't put polyester filler (aka bondo, mud) over epoxy. I prefer actual fill on bare metal and feathered out to perfect. No, it isn't easy. I've seen filler soften cured epoxy, and once primed, blocked and brought to final finish a few heat cycles can raise that up and make the finest surface development look driveway hack. My end game is always the same, the least amount of mil thickness. I want no more than 20 mils in total thickness. Yes, I have a gauge. Of note, the "Fat Chick" (Speed33) is overall about 12-16. In the days of lacquer the max was 12 to avoid cracks later on, and it's film build was alway less than urethane or enamels. Today's urethanes build up thicker, more mil thickness is acceptable because it's inherently less brittle than lacquers. Way less.

All that verbal excrement aside, when you find those correction areas I'll always advise fills on bare metal. Another warning, not all polyester primers are created equal. Most do not want to be put over etching primers, and they too perform better over sanded or lightly ground bare metal. Most of em don't even like actual acid etch surfaces like metal prep. I think it has to do with having a coarse enough surface to bite before the chemical cure is final. Too fine, ain't stuck. My .05

 

This is probably the most important part of the process-Zinc Phosphate coating of the steel. This is what most manufacturers do to steel parts and bodies. It's the first and best layer of corrosion protection but still needs a good quality primer and paint system to complete the whole refinish process.

 

This may make some guys heads spin right off but we get reps come through the shop all the time and what there saying now defines logic. PPG rep said no need to scuff coat anylonger clean seal and paint,3M says apply seam seal direct to coat no scuff needed apply fill to coat direct no scuff there point is there guys are making there product to adhear thus way take it how ever you want but I'm in the scuff camp on this one. Your painters sand coat almost to bear metal and some times to metal and all they do is seal and paint with no problems .