i just just wondering if it was ok to leave a car in primer outside for a while. i dont know if its porous or not and will start to rust but im about to do some bodywork and wont be able to paint it for a little while and it is my daily driver.

 

I would not do it. Primer is porous. And will rust if left out long enuff.this car i bought i don't know how long it was left out side. But all they did was but primmer on it.. See all that stuff. Thats rust. I but rustmort on it.

 

if you leave it with primer outside, it will absorb water, dirt and everything else. Even if you don't see rust, once you paint, most of your new paint will start bubbling anyway.

I don't know how much time and money you want to invest into bodywork on your car, but if it were me and I was doing full resto on the body, I'd probably just buy a $100 junker, drive it for 3 months and sell it. The beauty of old cars is that as long as they can move themselves, they really don't depriciate in value anymore after a certain point

 

You can get primer that is also a sealer, such as PPG Epoxy Primer. You can leave this indeffinatly and not have to worry about rust trough.

 

I am not an expert at this, but I am about to do my first car and been doing a lot of reading up on the subject.

A lot of primers today can be used as sealers. Sealing coat is usually thinner than regular one and I think you add more reducer, but I could be lying.

The whole goal of sealing is so the color layer is not absorbed by the primer layer as much. So when you seal, you don't have to use as much color to get uniform coverage as you would have to do without sealing.

As far as I know, sealer does nothing to protect from the elements. Although epoxy in general is way better at protecting the metal than 2K primer. I am going with 1-2 coats of epoxy under 2k just for that, but you have to remember it is still a primer.

 

As stated previously, PPG Epoxy primer is a primer sealer. It is made to be sprayed onto bare metel, and left. It does not require a top coat to protect it or the metal.

You can leave it on with no worries.


This months car craft did just that on a 69 Camaro.


They sprayed the PPG Epoxy, then added a hokey puck stripe. And left it at that, no clear, no other coat.

This is the stuff the street rodders are using on their 50's style 'suade' street rods.

If they feel it is okay to leave on their old rods, I am sure it will be fine on our cars.

 

Not to start an argument, but there are definitely differences of opinion. Just want to put a warning out to those who think leaving only primer will last you forever.

This is the response I got for a somewhat related question: http://www.autobodystore.com/cgi-bin....pl?read=29579.

so I thought to post the response here. No matter what kind of primer it is, it will always be just that "a primer" and that applies to not just cars. Sealing primer is when a primer can be used as a sealer. The way you do it is over reduce it and then spray one thin coat. Now how is a more reduced, thinner coat going to protect the car better than original material when nothing else but the reducer ratio changes?

Len from that board has over 35 years of painting cars, and so do quite a few other guys on that board. I've been reading that site for a while and based on their responses, I have a lot of respect for every single sentence those guys type.


And btw, body prep can take months. I've seen magazine guys do entire paint job in 4 days without a paint booth. Those guys don't exactly do things for quality. Then again, when you race the car, the way it looks is not their primary (nor secondary) concern.

Then again, each one of us has to make a choice how much effort to put in, and what kind of results you want.

 

Sorry to break hearts, but epoxy is the best holdout there is and has been proven by GM and other manufacturers. (as well as paint manufacturers) Epoxy primers are not like other primers, They are not for build, and as such, are not as porous. PPG's DP epoxies actually create a vinyl coating that protects steel like no other. It also creates the best adhesion to prep steel for paint. BUT...It is not the DO ALL EnD ALL!! It does not work indefinitely...studies that were done, show hundreds, and thousands of hours in moisture (and saline/moisture) environments. And while it does a fantastic job, it does not STOP moisture.

 

Can u paint on top of the epoxy primer? I was going to spray satin black ace paint on mine just to hold on until it gets painted. Wll that work? Thanks

 

yes, since primer's job is to go between the metal and the paint, it would be a pretty safe assumption that you can paint over it.

You would only have to use 2K primer if you want to level the surface because urathane primers are generally softer (easier to sand) and can build up faster than epoxy to fill low spots.

The only thing you have to be careful is that you have to paint within a recoat window for the primer you are using. They are all different, some are 2-3 days, the one I am using is 7. If you wait longer than that, you should scuff the surface, apply another thin coat of primer and then paint within the recoat window.

The paint you use must be a single stage paint, not a base coat. Just like primer, base coat paints (the ones meant to be clear coated) only give you color, they do not provide protectection from the elements.

 

DP90 satin black primer.

 

mm to be fair, wouldnt the same test with a fully painted vehicle prove the same thing?

 

Yep, they actually did testing without paint, with paint, without epoxy and painted, with epoxy and painted...
GM puts out a comprehensive list of "approved products" every few years.