I am new to this and understanding much of what you all have said. Have any of you used the Spray Max 2K aerosol primer? It is supposed to be very good and also seals. I have a 26T body I recently sanded down ( very little if any body work required) and having a hard time deciding what primer I should use! Some say rustoleum sucks, some like it. Bottom line is for a project like mine (rather small), what should I put down on the car prior to taking it to a pro to paint it?
I have to be careful in what everyone understands to be expoxy paint etc. What my understanding of a two pack epoxy undercoat to do is seal the panel it is applied to. It is correct that primner is porous hence why a panel repaired and primed and not painted will rust - the primer is not a sealer where as the epoxy primer is. A panel painted in a good quality expoxy could be left outside to the elements and not show any sign of rust - a bloody good development and step forward in the technology available to us. So What I believe to be a good step needs to be considered within the context of the products you are using
Not true Epoxy is moisture resistant, not moisture proof. I've striped many panels back to metal due to rust forming under the epoxy.
Because they didn't metal prep it prior to the epoxy and it flash rusted......you can't always see the rust right away, even an hour between bare metal and metal prep is enough to start the rusting process all over again.
I asked my DuPont rep about this a few years ago and couldn't get a straight answer. My question was , do you spread the filler over the primer un-sanded? Most of the epoxy primers are considered non sanding primers. PPG's DP used to be a bitch to nib sand. Anyway, how would you get the filler to properly feather into the orange peel texture? I could see sanding all the peel out with 180 and coating over that, but what a pain in the ass! I use Rage, but on this old metal I have found that its better to walk away for a while when applying to raw steel or it doesn't feather well when you finish sand it. I'll let the initial coat cure all day if I can help it.Otherwise, the edge always breaks loose. At my day job on this new stuff where everything is galvanealed it sticks beautifully. So far, I have not tried mud over epoxy. If I do I will let it cure for a few days and then sand it first.
my style has been to metal work the panel up as far as you can go spray a light coat of etch primer, allow it to dry then the two pack expoxy - walk away and let it dry - normally my last job for the day and it can cure/dry overnight without me loosing time waiting. Next day use your filler and spray the top cover - again walking away and letting the paint do its thing. It may be time consuming but roman was not built in a day. I started this process in 1998 when rebuilding a 1953 chrysler convertible (rotten pig to start with) and today it sits in a museum and nothing has ever moved or needed redoing. Car has been driven on the road so is not a trailer queen. Took a bit longer however the results were excellent. Again I need to stress I live in a country where we have high humidity and we have to look at all these steps to make sure we doit right - the first time. Consumer law is tough on you and shows no mercy when you plead with a judge that you acted with the clients best of intentions and the job still failed.
I always Epoxy first-the reason? well, if I have welded in a patch panel, for instance, there is no way that even as careful as I am that there wont' be some type of minute hole that I missed-now, if I put Bondo on unprimed Metal, and top-coated it, the backside of my weld is exposed-add water (and the fact that Bondo has talc in it, and will absorb the water) and voila! you have rust UNDER your Bondo- If you put the Bondo on within the time recommended by the manufacture of the Epoxy (you do read the p-sheet-right?) you will have 0 problems-with the Epoxy I use, it's 24 hours-if it's beyond 24 hours, scuff it with 180, Bondo-simple, and you will not have rust UNDER your work-and don't forget to Epoxy the backside-
I'm kinda old school and whether I'm doing lead or mud, I DA the metal surface with 80 grit, wipe with laquer thinner and go from there. Haven't had anything lift in 30 years, but I'm old so what do I know?
Please remember we are talking about a high humidity country here 80-90% is very common. In the lacquer days paint failure did happen alot. If you HAD to paint on a humid day you really had to try and warm the primer to try and evaporate the moisture the lacquer primer had absorbed, or else you would get "humidity blisters", small tiny blisters in the paint that would shrink or enlarge depending in the heat of the day. When you popped a large blister there would be water there!!! Paint failure in 2pak paint doesnt really happen so much as the moisture would have to get in to the paint itself, or between the paint layers at least, and this doesnt really happen when spraying in a dehumidfied, heated booth with dehumidified air supply. If you are talking adhesion failure, you are right, along with the rust under the bog, the paint wont have adhered very well to those areas, and given time, will crack and fall off. The blisters around the edges of the bog is the FIRST sign of trouble, not the last! Also, I dont consider any primer to be water tight. I will always strip off any primers if I have to gaurantee the job from start to finish. I tend to paint cars for the hot rodders in the lower to middle financial reserves bracket so to speak, and many of them have prepped thier cars themselves, so have seen all these problems arise!!! Cant gaurantee their work ofcourse!!
Just to bring up this debate again....we recently repainted this Morris Minor which had been bogged over the bare metal. This was an older restoration so the 2k paint had been on there for quite a few years. As you can see in the pics, where we dug out a "bubble" in the paint, there was a very brown rust stain on the metal surface, causing the bog, and thus, the paint to bubble. (Painters always get the blame!!) The panels would've been dry when bogged, (you cant bog in the rain!!), the moisture would've absorbed into the bog when the repairs were done...even more so if left overnight before being primed!! With our common 80 -90% humidity, I see this alot in NZ. Bogging over bare metal, in a high humidity climate, does not last!!
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