Technical Difference in Primers

You and I are in agreement. I've mentioned it before but never really had the answer covered.
So, you've got a panel, partial old paint with a portion that has some heavier rust. It's on an old car with thick metal so the rusted portion is still stable but has pits or small "pock marks". You rice cake the panel and DA it with 80 grit. Now you are at clean fresh metal like the day it was made but the heavily rusted area shows little pits that have rust in its craters.
So, Paint Guru, what do you do?
1. Use something like an acid or ospho on that area to kill (neutralize) the rust?
2. You simply spray over it with epoxy primer?
3. You blast the pits out with media or do the best you can with a wire wheel in a drill?
What say you Guru?

 

Idk? That's why I'm trying it on a OT 4x4 k5 blazer to see what happens.
How can you tell what the long standing results are ? You try it for yourself or take it on advisement from others who did.

Yes that's it.
I had a catastrophic failure that is probably attributed to oshpo. Multi million dollar lab couldn't find the problem, manufacturer said there was nothing they found to cause it. Either in my work or their product. The only variable is ospho or they keeping their mouth shut about their stuff. Funny though, they comped me a truck load of products for my troubles

 

PG,
Great thread and thanks for all the info. I have a new chassis which I'm sanding for primer. I'm assuming epoxy would be your suggestion. What grit should the steel be before epoxy ? I've found epoxy to be difficult to sand. What grit does the epoxy need to be before urethane primer ? It's a high boy, so the frame will have the same color as the body. Thanks in advance.

 

Lol I by no means recommend it, but 300-1 is sprayable body filler (polyester primer) so it technically should fill the scratch, I have warned against it at the shop but it is what it is, but I will say this, they did a full size van the other day and painted black and sat in the sun for a week and looked pretty damn good. I don't even like primer over 80 grit, I prefer 180, but you wouldn't believe how hacked up the body work is and how well it turns out. But like you said, even with other brands of paint, you don't know what its gonna look like 5 years down the road.

 

I am against any acid or ospho under our products. Our epoxy has rust inhibitors built in, so if you sand the panel, just wire brush over the pits, degrease with a automotive wax and grease remover and prime with epoxy and done. Or you could blast as well, I would not have an issue with either one as long as you are not soda blasting.

I can't really talk for other brands, but epoxy can be built 1000 different ways, which can result in rust coming back etc. I am completely against building economy epoxy because of issues where all the rust cant be removed. I will say even if you could not get all the rust, our epoxy will still work excellent over those areas. I couldn't give a recommendation with another brand because of ways in which they perform.

 

Thanks! Answers all questions. I still
need to phone you for product (thanks for the contact). Planning on ordering epoxy primer.

 

Use Epoxy, and I would recommend a polyurethane topcoat for the chassis for chip resistance and durability.
Use 180 if you can to initially sand chassis. If epoxy doesn't sand good, just give it a little more time to dry. If you prefer to sand Urethane, just sand epoxy with between 180-320 then use the urethane primer on top if you think it is needed. I personally wouldn't sand epoxy with 320 just to prime over with urethane. Stick with 180 or 220. Good Luck!

 

Paint guru, this is such a good thread. In my eyes the best advice you gave is how important TDS sheets are, they tell everything if you can understand the terms that are used. I bought a gallon of cromax epoxy for a price i couldnt resist, sure enough on the tds it said DO NOT APPLY POLYESTER FILLERS OVERTOP.
Normally i would, but glad i read it or i would have a huge PITA later on.
just goes to show primers/paints have specific uses.

 

Talking about million dollar lab, last week I was at one of our paint stores that we wholesale to they have our line and a real popular paint line, and the paint rep from one of the big 5 paint companies was there looking at a warranty claim and the paint rep told the owner with the paint issue, " we will send this paint chip (off the car) to our lab to do a burn test to verify all the products are all ours.
Lol never in my life have I heard of a burn test on paint chips verify products, when the guy with the car left, I asked the paint rep, how can you verify products with a burn test? He looked at me, with that same look a cop gives when he smells beer on your breath, he took the paint chip and threw in the trash and said well here are the lab results, we can't find anything wrong with our products , but we will give him products to redo the car. What a dick!

 

Wow!
Now that's screwed up.
When I heard back from them, I told the guy this , "in my heart I know that I didn't cut any corners and I wouldn't do anything different. If you can't find anything wrong within your testing, what should I do differently? I'm sorta gun shy to go thru all of that again especially with the same products and same methods."
"Gun shy" translated into sidelining that project for 5 years.

 

I agree, even if you get reimbursed for the work, you still have to do it all over again. Which isn't near as fun, and any tiny thing that goes wrong on the second attempt really pisses you off!

 

Great information being shared here. PG, I like that this hasn't turned into a commercial for one particular paint company. All this info can be used with any paint lines products, just very good general information.

The shame of the story about that rep throwing the paint chips in the trash is that he is the front line of a major paint company. Again, nice of you not to call them out on this. Every paint company is only as good as their reps out on the street. Some are great, while others give the company a bad name, or at least a not so good name.

 

I agree with Hot Rod 47 and P.G. and not slamming anyone. I had a Canadian Rep. that was outstanding and a hell of a good painter.

 

Yep, but I don't think that reimbursement happens.
you need to do 22 jobs with the free material to make it even out.
They give you enough to to 3-4 jobs.
They give you the same damn products that failed too.
Their cost on the stuff is pennies on the retail dollar I'm sure.
Crazy shit I tell you.

 

Only got enough material to do the job over never any extra. Washing one down and redue all the prep work really sucks. The only one that helped was the Canadian Rep. Had to strip a motor home and he stayed from start to finish, furnished food and beverages and took the whole crew out to a big dinner after it was over.

 

Question -

How long can urethane 2k primer sit or remain in long term storage before block sanding? And is it better to sit with the skin unbroken or sanded.

The backstory,
It was time to advance a project and we took advantage of the recent short weeks and holidays to do this. Filler work was finished, epoxy primed, usc 300-1 polyester filler block sanded, then 2 coats of urethane filler primer where applied. Now,,,, it needs to sit again.

My thinking, better judgement and budget says to let it sit with the skin unbroken until its time to paint it. Its possible that it could sit for 5 weeks or another 5 years- there's just no way to tell. It may even be sold at some point.
Its doubtful there will be any need for another coat of filler primer after this one is blocked. My thinking is- When its time to paint, final block the urethane, epoxy sealer and paint. That would also be sure that any and all shrinkage may happen takes place.

We could block it, then epoxy sealer but it will sit like that in long term storage. Some place in the future that epoxy sealer would need to be completely scuffed and reapplied. Not bad on the big areas but its a royal pita in all the detail areas, and that's most likely where an area gets missed.

My buddy is pushing me to get it thru onto paint, at least cut in. Then reassembly can be done as time allows.
Existing Schedules, prior commitments and budgets are in the way. It's also different storing a finish painted project than one that needs paint.

 

PG, thanks for the advice. Such a good thread it is much appreciated. Got a question. I read on another post on body work a hammer suggested using PPG CRE epoxy primer. I know were not trying to push brands, I just would like your opinion of it was. Thanks.

 

Some urethane primers become brittle without top coat, I would prefer to see in epoxy, if its going to sit. I honestly don't know why this occurs with other brands of urethane primers, they will actually peel up, I think its the amount of talc that some manufacturers use to help sandability, but on the flip side you do run the risk of this happening.

If it was me, I would use epoxy as sealer, and spray a urethane single stage on there, or just leave in epoxy.

 

That sounds like take it thru to paint then.

 

Now I'm thorughly confused and hoping my work doesn't all fall off. I urethane primed everything, did my body work, filler minimal, polyester filled and am spraying urethane primer tomorrow.
What should I put on top of the urethane to keep it protected for hopefully not over a year while I shake it out?

 

I've been following this thread and there's tons of great info. I plan on having my car dipped eventually. The company i am considering to do this neutralizes the acid afterwards, rinses with water and then treats the metal with a rust preventative coating which I am guessing is some sort of phosphoric acid solution. What can be done to prevent incompatibility with epoxy primer down the road??

 

Devin, I had been sanding my panels to bare metal and using ospho on them and then this thread came along. I was worried about the acid compatibility as well.
So I tried using #80 on my DA and it seems to sand right off and back to clean metal. I plan to continue using Ospho and sand very clean and thoroughly, then use cleaner/degreaser as recommended prior to using epoxy primer.

I also did a test with SEM primer. I applied it over a section of dried Ospho as well as a patch of Ospho which was then sanded off as mentioned above.
After the primer was dried, I tried sanding it off of each section to check for adhesion. The adhesion on the Ospho section was sketchy. The adhesion on the Opsho/sanded section was excellent. I was convinced.

I am learning a ton on this thread and am happy to hear advice on this from anyone with experience.

As a sidebar, I also tried that test over a patch of Gibbs, applied heavy and left to "dry". Very good adhesion. (I'm not recommending this, but was surprised nonetheless)

 

A lot of great info here. Thanks.

 

Cool. I worry about the seams and such. The dipping place will epoxy prime after dipping also but I wanted to do some lead work etc. it still may be best to prime the damn thing and then just sand off sections for leading.

 

Guru , I'm using ppg delfleat epoxy and how cold can I paint it . I know the top coats need to be with a metal temp of 50 or above . Doing some big quarters and that part of my shop is hard to heat . Would like to epoxy as soon as I get bodywork hammered and leaded . Filler primer and filler won't get done till spring . You can see the size I'm talking about on site listed below . Will be doing one side at a time as I have to turn the truck around for room . Thanks ahead of time , Blue

 

As others have said, great info here. I know it has been stated that just sanding down to bare metal and then epoxy priming is the best course of action, but my truck is in bad shape, as in, there is basically no paint left anywhere and there is a lot of rust. I am going to do an acid dip using citric acid with a sodium bicarb nutrilization at home. Does anyone see any issues using the citric acid and then the epoxy?

 

I am not familiar with PPG CRE Epoxy, I have looked at the tech sheet, nothing super special about it, not recommend for galvanized or galvaneal. It is in their performance coatings line which is a economical industrial coatings system they have. I have never seen that in the field, I've seen their ALK-200 enamel line in the Performance Coating line. It is what it is, its a paint for manufacturers who paint because they have to, not because they want to. The epoxy might be good for restoration, but PPG didn't build for that particular purpose. I would consult a PPG rep only problem is the Performance Coating and the ppg Automotive will probably have 2 different reps, they usually are that way. Also another Problem is with epoxy you don't see issues until about 6 plus years down the road.

 

Urethane Primer isn't really meant to keep long term, unexposed. I know a lot of people do, and some are fine for long term storage, however there are quite a few that peel, and its hard to keep up with all the brands out there that will, yours might be fine. If it does peel, then you have to sand it off, if it doesn't then you are good to go.
One thing you can do is after its primed, sand and paint. This actually does 2 things, it will help protect porous products underneath and the gloss of the paint helps see any imperfections so you can fix before final paint job.

 

People use different products to dip metals. I would ask for a msds for their chemical bath they use, then take that to a paint rep for whos product you will be using the rest of the way up.

 

Below 55 paint doesn't like to crosslink. It will dry to touch because of solvent evaporation but won't be fully cured if below 55 for long periods of time.