CNH Iron gaurd primer

redgems

Member

Gentlemen,
I am having a MM U painted After blast and prep my painter insists on using CNH Iron Gaurd primer (Red) and the paint is prarie gold#2 Sherwin Williams Acrylic Urathane Automotive. What he has done so far looks good However I am concerned that its not the eppoxy that S/W recommended. He showed me the Iron gaurd fills in better, Also was afraid of red tint under yellow But so far good on pieces hes done. Will I have problems down the road ???
Tony
 
I'm not sure but I think Iron Guard primer is an old fashion alkyd primer. He likes it because its easy to use with no recoat window to contend with and is easy to sand between coats. Epoxy primer has a recoat window, contains isocyanides and doesn't sand very good. There is a night and day difference in the quality of these two primers. I'm sure any body guy would rather use an alkyd primer if it was any good. They put up with the epoxy because its so much better. Then today most automotive finishes are geared to be used over epoxy primers so you would be bucking the system to use something else. The primer is the foundation of the finish and if you start with junk, it really doesn't matter what you topcoat it with. Both systems will work but the epoxy primer will last much longer and will protect from rust better. I believe if I were going to use Iron Guard primer I would continue with an alkyd enamel topcoat rather than spending the money for a better topcoat.

I have no doubt Iron Guard primer fills better because epoxy primers are not formulated for that purpose. The epoxy primer is put on first and if filling is needed a filler primer is applied over the epoxy which is sandable.
A CNH makes a gray primer or they also make a medium yellow primer that would be better for yellow however urethane covers pretty good so it should cover with two coats.
 
The epoxy primer recommended by SW would have been the better option especialy if it is the high solids high build product. It is sandable within 30 mins fills nicely and very smooth profile when sanded with 400 grit paper. Epoxies are catalized with amine not isocyanate and will provide far greater durabilty than the Iron Guard primer. Iron Guard primer does have a critical recoat period whereas the epoxy does not. However, the alkyd primer is a 4th the cost of the epoxy.
 
He should've used the epoxy primer. Then use a surfacer like Primeez from Martin Senour. It's also sandable. I bought Dupont's surfacer, but I like Martin Senour's the best. Then top coat with the SW paint I have heard SW makes paint for
PPG and Martin Senour. Hal
PS: The surfacer comes in gray too.
 

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