Ok, so I have some ppg JP215 self etching primer that I'm going to use on my car. After reading the datasheet on it, I get the idea that I should only apply this stuff to metal and nothing else. I take this to mean that I need to strip the entire panel to bare metal before spraying the etch primer. Is that correct? Should I not leave any factory primer remaining?

 

You only need to apply self etch to the bare metal, as the rest of the panel is already primed.

First off, I would recommend if you can, to return the self etch and go to an epoxy primer. Epoxy can be put over anything. The self etch will only be good for bare metal. With as much plastic as these cars have, you will eventually need to epoxy something. I will fast forward throught some reasons why shops use certain products but its basically for speed and costs and doesnt apply since this will be a one time at home job. Basically you are having two products in your inventory when you only need one.

To leave the factory primer is a judment call. If you do use the self etch and spot prime, you will have some overlap onto existing primer which is fine, just make sure to keep it to a bare minimum (1/2"or so). I would highly recommend against self etching over existing primer for two reasons. You may get away with it, you may not. If you dont get away with it you have wasted product and time. Also, there is nothing to gain by priming primer.

 

Thanks for the reply. I didn't know if the etch primer might blister any paint that was there or cause some other adhesion problem. The datasheet only lists metal surfaces as the substrate. I am concerned about the factory primer anyway as it doesn't seem to have fully sealed the metal. It's allowing rust to form where it's exposed and I don't think it's only in damaged or chipped areas.

I'd appreciate some more information about it after you eat. Thanks.

 

My semi-retired body guy used both.
Some spots where dings were excessive. Closed original holes on deck lid for newer '97 wing, and used etching there.
Chemical stripped the hood completely and etched, too

 

Paint should be on before Christmas!

Brian

 

The self etching primer- as stated above is only really good over bare metal- it doesn't stick well to body filler or paints. I used to spray whole panels with it, but now i just spray the areas of bare metal. When it dries i use a high build primer so i can block sand it all. when i'm done block sanding i'll use a sealer before i use color.

 

Man I want to see that '56 without a cover.

 

I was afraid it might not like paint underneath given that it's designed to bond to the metal. I'll finish stripping the panels to bare metal since I don't trust the primer to not have specs of rust under it in places. The panels are fairly straight, but the roof does have a couple of small dings in it that will need some filler, but probably only glazing putty. Do you think it will be ok to do that after I put sealer on it? I just want to get it sealed as quickly as possible because the car is living outside right now. I was planning to just put JP385 2K sealer on top of the etch.

 

Absolutely!

He has a '57 Vette, and another '58 Chev. Those cars convinced me that he was the guy for me.

Taking long time, but it's getting done right. I'm an original owner.

 

I think if you scuff up the sealer pretty well you could use some glazing puddy on top of it....just remember to respray the sealer over the puddy before you get into the color. the color doesn't like the surface of puddies!

 

2k Sealers don't like temps below 60 degrees before final paint. Check the data sheet. Paint shop guy brought this to my attention. I'm in heated shop.

Sealer before color is must for me. Weird chemical reactions can come from anywhere - just good sense and insurance.

 

What do you mean exactly? Are you saying that if the sealed surface gets below 60F once, then the sealer will cause problems with the top coat?

I'm just trying to stop a fly away paint problem that's turning into a rust problem. I didn't really plan to put any top coat on anytime soon. I just wanted to remove and stop the rust and seal the surface. I planned to leave it gray until it can be painted right by somebody that isn't me.

 

Sealer is only applied after all filler/glaze work and sufacer has been blocked. The only purpose of sealer is the give the color coat a uniform base, and to keep the filler/glaze areas from showing through. To apply sealer before glaze would be a complete waste of money and product.

On a side note, Im not sure is sealer is watertite, I will check on Monday. I dont see why it would not be, I just dont know.

 

Any product should be sprayed above 60F. I never spray below 75F. Once it has dried, it can be at any temp. Anytime you sparay below 75F your flash time between coats increases. The flash times in relation to tempature sprayed at will be available in the products "P-sheets".

 

I would use JP37x epoxy primer to go on top of the etch instead of the JP385 urethane 2k sealer, but the datasheet for the epoxy primer doesn't list JP215 (etch) as one of the "Compatible Surfaces". On the other hand it does state, "cleaned, sanded and ETCH PRIMED STEEL". Yet they don't list their own etch product as being specifically suitable. Any PPG Shop-Line decoding experts out there that can resolve this conflict?

I just want it to be sealed from the environment, yet still be able to work on top of it later without stripping. I don't mind if I have to add a fresh layer or scuff/sand it to make it usable in the future. I realize that I have to reseal any filler or sandable primer I add. I'm not married to sealer or epoxy, I just want something that works and is somewhat idiot proof. The pot life of the epoxy is allot nicer than the sealer, that's for sure. 8hr vs. 1hr.

 

The best solution is to forget the etch and sealer, and go with Epoxy. Epoxy will go over anything, and is watertite. Later on when you want to topcoat/ bodywork, just scuff the Epoxy and go.

The reason to use Etch is that it is cheaper than Epoxy. If you are say Carstar, and can replace 2 Gal of Epoxy with etch at a savings of $10 a gal, you get a $1,000 in savings per year. If you are doing one car, buy etch and epoxy, the etch is a 100% loss.

As a disclaimer some P-sheets will say to use Etch on bare metal the Epoxy over that. From experience as long as you are in a quality product line eg. Spies, PPG, RM, I have had no issues with Epoxy on bare metal. Omni/Shopline are the exact same product within the PPG family.

 

Thanks for the reply, but I want to be sure that the rust is dead. I've had epoxy rust thru even though I used naval jelly to kill it. And this was when it was still lead based. I'll take the sealer back I think and get some epoxy primer. I used a rust killer product called GEM that was recommended by the paint store and even a body shop. Maybe I'll just stick with that and shoot epoxy right on the overnight cured bare surface skipping the etch and the sealer. GEM is a phosphoric acid product that converts rust into iron phosphate effectively killing it. It wasn't real bad, but bad enough that it still shows a dark area after sanding with 80 Grit. I can cut thru it if I try, but I don't want to leave divits in the panel.

 

Put some so-called "aircraft" stripper from an aerosol can. I suspect this is not how they really strip aircraft. It did peel up the base/clear very well but only removed about half the remaining factory primer. Rinsed it off in the driveway and took it to the local car-wash to blast out the remnants of the toxins. Dried it good and sanded it some more with 80 grit and got the loose factory primer and all of the remaining blue.

I went to the paint store and bought some JP375 grey epoxy primer along with its associated hardener. I've decided that I'm going to sand it down real good, treat it with GEM and wait until morning. It's supposed to rain tomorrow afternoon, so I'm concerned about painting it at all right now. The datasheet says that 2 coats will air-dry in 30 minutes. Does that mean I can let rain fall on it several hours later? I could cover it with plastic and not drive it if necessary.

I think that using the rust killer and epoxy is the simplest way to stop the rust and seal the surface. My previous experience with "real" DP epoxy was that it was an amazingly durable surface that was impervious to the elements. I really like the idea of only having to mix up one paint batch that has an 8 hour pot life, but dries in 15 minutes.

Anyone with experience using the shop-line epoxy (JP37x) primers? Should I reduce the second coat a little more so that it seals better? All advice welcome.