Technical Difference in Primers

PG, thanks , that's what I was wanting to hear, if it would be a stable base for the top coat. At most the job would be 2 colors and plenty of clear to sand smooth. 2K looks like a winner
I have had the experience of the lower materials bleed up during multi color candy jobs on helmets and bikes trying to get color on in 1 pass doing fog work and fade away.
Thanks for the tech Thread

 

Couple of tips for bleed through is a inner coat clear or some cheap quick 2k clear, then come back next day. My avatar if you zoom in on it, you will see a lot of depth with the flames, I layered between candy coats with Matrix MPB-500 mixed 1:1 with urethane reducer.

 

what about alkyd oil based enamel primer? with hardener. the type you see at most tractor supply store's. what kind of top coats can be used over it. I have used it, with good results, but always used the same brand enamel paint over it.

 

Alkyd Oil based primers do ok for industrial applications, but for long term its very similar to lacquer. It doesn't sand very well, but it does have some adhesion properties to metal, but nothing in comparison to epoxy. As far as the Tractor supply store Enamel top coats - with weather and sun exposure, it just won't hold up. It will not keep a gloss long term, you can make that stuff slick out super nice but its only temporary. A lot of people think the enamels at the tractor supply stores last a long time, it doesn't. The blacks turn gray, the reds turn pink ect over time ( I have seen reds go pink in as little as 6 months in South Georgia).
Also its extremely difficult to repair over those type enamels. Its very easy for the product to lift or wrinkle. I would stir clear of those type of coatings, even if I was painting a tractor. So just spend $150 for 2 sprayable gallons of epoxy and about $150 for a gallon of Polyurethane or Acrylic Urethane and a quart of hardener, and never have a doubt in your mind about durability, repair ability and color retention.

 

As Paint Guru says. I don't think you can beat modern paints formulated for automotive top coats.

 

can I spray epoxy over the alkyd ? and what about spraying urethane over it? I have a cab already sprayed over bare metal and filler that wont get painted for some time.

 

I wont metal prep a bare metal panel with acid (OSPHO) after I had an adhesion problem with HOK epoxy primer KP2CF!I had to strip a roof and this was after rinsing the ospho residue off.BURN ME ONCE!

 

Ospho is great stuff !
Epoxy primer is great stuff!

Some epoxy primers just don't like ospho - not at all. Some epoxy will tolerate acid some don't
Some epoxy chemistry gets along great with ospho

 

My personal stuff if I can sand to metal I won't use ospho or any metal etching products. I will stick with epoxy throughout the process.

 

How big are your bare metal spots? Bigger than a basketball area? If not you could spot prime with anything.
I would strip the alkyd primer to be honest for a automotive restoration. It won't do you much good to sandwich your alkyd between urethane or epoxy. But if stripping is out of the question epoxy will help seal everything down however if the alkyd losses adhesion the epoxy will peel with it.
Let me ask you this because either one might not be compatible, what does the primer can say to reduce with?

 

the entire cab was bare metal.so can I sand the alkyd primer with 180 then seal with epoxy primer? not sure what it says on can, just use lacquer thinner with catalyst.

 

Hi PaintGuru.I have a question that I have never been able to get a straight answer to.
Could zinc chromate be used for the first paint on bare metal before using automotive paints.YES,I know not to sand the zinc chromate.Very Nasty dust particles.Thanks.
Good luck.Have fun.Be safe.
Leo

 

What I would do first if you have some epoxy there already. Sand with 180, clean and tape up and small area, roughly 6"x6". Prime in that area with epoxy. Let it sit for a couple of days. Then take a razor blade and make cross hatches all the way to the metal (see attached picture ) then put masking tape over the area and rub fast to generate a good bond,then pull the tape off almost the speed of pulling a band-aid off. If a good bit of paint comes off on the masking tape, it's not going to work.

 

I am not too familiar with coatings that contain chromates. I will ask our chemist tomorrow, he handles all the Aerospace coatings which is where you mainly see the chromates.

 

Paint Guru, I have all the bed parts for my 52 pickup done in this manner, stripped to bare metal, body work done, sprayed with Dupli Color lacquer primer, blocked and primed again with same product. Prior to painting could/should I use 2K urethane primer before color. The color is Dupli Color garage shop product?

 

I wouldn't spend the money, you have a 1k lacquer primer then a 1k lacquer topcoat. Using a 2k sealer will not help the longevity. If you are afraid you might see light sand scratches from aggressive block sanding, use a cheap enamel sealer. Now if you were putting a 2k urethane or base clear as the topcoat , I would say yes put the 2k because it does help keep color and gloss. But lacquer topcoat will not keep that deep color long enough for you to benefit from using a 2k sealer. Can you return the Duplicolor? What color are you going with?

 

thanks for your time and advice Guru. I'll try your test on a piece I cut from the bed. incase it doesnt fail I wont have to fill cuts somewhere on the cab.

 

I talked to our chemist, he said zinc chromate comes in powder form, so it has to have a wetting agent (primer, solvent etc) but if it were suspended in a solvent then yes you could spray that first then topcoat. But he said it's old technology for aerospace and military spec products. We have better technology metal adhesion promoters now. We actually just came out with a direct to metal reducer, any of our Paint if you use this reducer, converts it to a direct to metal product. It provides great adhesion and corrision protection. Very neat stuff!!

 

Wow !!!
The secret magic bullet.

 

Hi Paint Guru.Thanks for your time to answer my query.Good info.
Good luck.Have fun.Be safe.
Leo

 

PaintGuru,
When you say "our paint" what brand are you referring to? Do you sell direct or only to re-sellers?

 

Both, if we have a jobber in your area we call them. If they don't follow through we sell direct. But we are very small with distributors. The problem is our pricing is very competitive so a jobber will take on our line just to keep others from getting it, which sucks. But we protect our jobbers as well because they really help push our brands. So if you wanna become a paint distributor. ........lol

 

Paint Guru, First thanks for the quick reply on the urethane. The color I'm going with is their dark blue but I'm mixing it 4:1 with their white to get the color I want on the truck. Thanks again for all the info you are dispensing on this thread !

 

You are probably wanting the color I just put down on my floor (but it was a metallic blue).
If you are not real particular on a shade of color for a project let me know. If I screw a color up in that family I will cut you a huge deal. I have a lot of maroon metallic but more on the redder side right now for some reason I would take $65 whole gallon acrylic urethane just to get it out of the way.

 

An excellent thread, however, self etch is actually a 2K, as it also uses an activator. That does make it a 2k paint, because it does need an activator to make the primer compete

 

Paint Guru, The color you put on your floor, looks very close to the color I start with, before I mix in the white. I would have considered buying that, if you come up with any more close to that, message me and we'll work out a deal. How much do you think I would need to do my truck complete? It is a 52 Chevy 1/2 ton step side completely disassembled off the frame, will be painting pieces separately.

 

A Self etch can request a second part which is a reduced acid that requires a lined can, it is not technically a activator. It doesn't require the 2nd part - look at all the self etch primers available in aerosol cans for one. Any Paint manufacturer could package both together, some do. I think the reason is the extra cost of a lined can.

If you put the self etch and the "activator" in a sealed lined, glass or plastic can and let it sit for 2 years it would still go back into solution. Now to your point I have seen Urethane primers that some Paint companies call self etch out there, but those are just that - urethane primers with an acid for corrision protection, but its not a self etch at all. Also some DIY companies put 2k on their self etching label, but there is no law about what you can put on a paint label, even though I completely disagree.

 

A note about self-etching primer. It ONLY goes on bare metal, nothing else.

Spraying it over any other paint, primer or filler can cause damage, that may not appear until well after the top-coat is done.

I have a former boss who learned this the very hard way, even though I warned him.

 

What to do on inside of body when you take all the wood out to replace with steel and you have some surface rust and old coating on body.Do you wire brush and epoxy or do you Ospho or what if you are not going to blast area.This is on a 35 Chevy Standard

 

The absolute quickest way to remove Paint and rust is a variable speed buffer and put the 8" sanding pad on, and go to town.

But in your case you have a lot of hard to reach spaces. Wire brush just over the rust and sand what you can by hand or with a sander. 180 grit would be the best but you could go 80 the first go around then 180 after that. Then use epoxy if you can. Or since this is interior a dtm urethane will work. But since you are going to have welds, epoxy will seal it where it will never rust around the seams.