The Stovebolt Site Forums The Shop Area Paint and Body Shop Need Advice - Bad Primer

This is what I get for going cheap I guess. We spent all of last Saturday blasting the cab of my 42 1/2 ton pickup. Got the interior as best we could , but the exterior was pristine. Monday morning, I rolled the cab out of the shop and sprayed the interior with Eastwood's rust encapsulator. That worked out great. I then applied a Yellow Zinc Chromate Primer from Triangle Coatings (Mil Spec TT-P-1757A) to the exterior. That went on great. My plan was to get the chromate on and then sand off as I needed for body filler and welded repairs. Idea was to keep the rust from coming back. My problem is that this has not hardened past the tacky stage. I still see my fingerprints in it when I touch it, though they seem to disappear. Sanding does not work, as it simply balls up. I tried some MEK on a rag, and it takes the Chromate off. Auto Stripper works better and faster. Should I go ahead and chemically strip the cab back to bare metal on the exterior and then shoot with another primer?

is that a two part system,what I mean is does it mix together with a catylist,or is it a spray bomb.those zinc primers should be dry(depending on temp ) in half an hour .try heating a small area with a hair dryer and see if it helps.if it was a two part you might have mixed it wrong ,then yes take it of and start over

Clint,

Was the chromate paint intended for automotive use? I would think it more suited to an offshore oil rig. I am not a body and paint man, so this is backyard advice. Get that stuff off the truck any way you need to...then, as they always say, pick a true automotive SYSTEM, and stick with it. That means brand Q's etch primer, brand Q's two part primer and brand Q's paint. This is a engineered system they made to work together. Doing the same job over and over gets quite old, at least for me.

Unless you are real experienced in automotive paint, go to a paint store (automotive) and ask what they would recommend. When it's done and looks beautiful your friends will have you painting their rigs.


Stuart.

I think zinc chromate primer is meant for aluminum - common in boating and airplanes - I vote to take it off

Bill

I am stripping my 55 down to bare metal then spraying the bare metal with a two-part etch primer, then a two part urethane primer. I plan to sand down to bare metal where I need to apply body filler.

This is the method that the auto paint shop recommended and was approved by all the body shops I spoke to and all the Stovebolters.

Good luck.
Michael

I only know that zinc chromate is used as a rust inhibitor on steel rolled goods or plates...it creates dangerous vapors when it is welded on or burned. This is bad stuff..be careful.

CLINT MEK! ZINC CHROMATE! That is definately aircraft stuff I agree with atomarc use an automotive approved system it will be a lot more user freindly and with alot better results and yes be carful the automotive stuff will harm you and the aircraft stuff will harm you 10 times faster than that, especially the MEK.
DS

the zink is good for your steel if you have time park it and it will harden a while back i had the same problem with a top coat i left it set after 4 days it did harden im glad i didnt touch it the military uses zink its good just let it set what made my paint harden was spraying water on it but i wouldnt do that with this just give it a few days it will harden

I can't call anyone a liar that says ZC is OK for steel because I don't know but this is the first I've heard of it being used on steel. I DO know that, as noted above, it's been used on aluminum for decades and yes it's bad stuff if you breath it in, both fumes and particulate. MEK is also bad stuff. Short term it'll dry up & crack your hands real bad. Long term it'll screw up your innards. It does penetrate your skin so wear chemical gloves if you do use it. FYI, in case you consider using alodine as a corrosion inhibitor, never, EVER, let MEK come into contact with alodine. That includes rags contaminated with each.

I don't know about aluminum...but I worked in a production weld shop for many years...the steel plates from the mill were coated with a yellow coating (zinc chromate)...we got an OSHA complaint and had the vendor discontinue its use because of its toxic nature.

First off stay away from the etch primer. :hammering: You don't need it with bare metal. Just use Epoxy Primer/Sealer. You can put High Fill 2K primer over etch. You have to seal it first with Epoxy then apply the 2K.

The only time you would need etch primer, is if the metal is slick and new and never been sanded or blasted. A sand blasted surface is perfect for paint adhesion, especially Epoxy.

Zinc Chromate is for aluminium as stated before. It doesn't need a hardener is usually sprayed from a rattle can. I used a lot of if in the USAF. It's also used on all military vehicles such as 6X6, and Hummers.

So anyway, just spray some 2 coats of Epoxy Sealer, then 2 or 3 coats of 2K and block sand with 320 wet or dry.

If you want to be cheap you can apply 2 or 3 coats of Lacquer Primer over the Epoxy and then block sand with 320 wet or dry.

Frank

Humble pie! I just did some research on Zinc Chromate...it is in fact a direct coating for aluminum to prevent corrosion. It can only be applied effectively to steel if the steel has been zinc, cadmium or phosphate coated.