epoxy primer wait time

[ywalk]

I am up against a close deadline for completing my "H". How long do I have to wait to apply body filler after spraying epoxy primer? tech sheet says 24 hours before sanding but I would like to rush that a bit if I could.
 

[CNKS]

What brand are you using? True epoxy primer is usually not sandable, at least the PPG version isn't. I put body filler on before the epoxy, if I did put it on after I would probably wait until the next day. Others may have a different answer. PPG Omni MP 170 that I use can be top coated in 30 minutes.
 

[ywalk]

I am using Nason ful poxy. sounds pretty much the same with topcoat after about 1 hour IIRC. I will give it as much time as possible with plenty of time in the sunshine and temp in the 80's. I was taught to put down the epoxy first to seal up the metal and give a good base for filler and high build primer etc, then finish with another coat of epoxy to act as a sealer before topcoat.
 

[Stephen Newell]

I also use the Nason Ful Poxy first before bondo. Depending on weather conditions when it is thoroughly dry enough to topcoat it's dry enough to bondo. Then I only spot reprime where I have been sanding the bondo. The next step, I coat the entire project with Evercoat Featherfil for sanding and leveling. With this product there is no recoat window to contend with and sands very will. On sheetmetal work where I'm uncertain if the bodywork is correct or not I use two different colors of Evercoat alternating color with each coat as a guidecoat to find the high and low spots. When I'm satisfied with the primer it can be topcoated with most finishes without recoating with epoxy again. I normally use Nason 2K Urethane.
 

[CNKS]

Every person has his opinion about body filler. It needs at least 80 grit some recommend coarser to get a good bond to the metal. With epoxy you are filling some of those 80 grit marks with primer. I think the person who told you to "seal" the metal was afraid the sanding did not get all the rust. When I sand there is no rust left and none appears before I get the body filler on. I suppose those who live in humid climates can't do that. To me (and I can't prove it, and many will disagree, which is ok), the epoxy will reduce adhesion, as the PRIMARY filler was made to go over bare metal.
 

[Red Ford]

It requires extra care to sand PPG epoxy primer, but it IS sandable. If you wait past the recoat window it MUST be sanded. The heavier it is applied(yes, it can be used for high build), the longer you need to wait before sanding. And, the longer you wait, the easier it is to sand.
 

[CNKS]

It can be smoothed up if there is a drip or run if I am very careful. I have done that. By not sandable I mean not like surfacers or primer surfacers or other high build primers or even some of the cheaper red oxide or lacquer primers. PPG recommends 1 or 2 coats for the Omni version. I sand it only if I have made a mistake. Not much sense in using it as a high build when there are much better products available. IMO epoxy should be used as the base coat on everything. If outside the window it has to be scuffed or sanded, makes no difference if it goes to bare metal as it has to be reapplied. I haven't used Nason, perhaps it is formulated differently that allows it to be applied thicker. I see no advantage in that either. PPG MP 170 is really thin, probably the reason PPG recommends two coats, used to be one. I have always used two because I am not skilled enough to get perfect coverage with one coat.
 

[Re Ford]

It depends on what you are doing. All the high build products I have tried are either too soft, too brittle, or don't have enough mechanical strength. Heavy epoxy application, lots of cure time, and skilled sanding, are the best I have found for my shop's jobs.
 

[Loren in WI]

Body filler will hold better on epoxy than on bare metal. I live in the rust belt, WI, also as a PPG master painter I was told at school to apply before body filler.
 

[CNKS]

With PPG Omni MP 182 surfacer I have had zero problems. It would take many applications of Omni MP 170 to do what you describe. To each his own.
 

[CNKS]

I try to follow the instructions that come with the product. Everyone including instructors have their own opinion. I wouldn't mind taking the courses you did, but at this point in my life I don't want to take the time and for me it is only a hobby. What I have done the last 10 years has never failed me.