Omni mp170 epoxy primer question

[Haley]

I am gearing up to sandblast and repaint a combine and have a few questions about the Omni line of paints from PPG.I reciently used Omni regular primer and paint to repaint a tool bed for a truck and was VERY pleased with the results.The question I have is that after sandblasting the combine and priming with the MP170 epoxy primer does it have to be sanded before I can spray my color or does it go on smooth enough to paint without sanding? After priming my tool bed it was kind of rough so I wet sanded it with 1500 grit paper and wound up with a nice mirror finish after the color dried.My concern is that there will be lots of places on this combine that will be awfully hard to sand if the primer does not go on smooth.This will be an every piece apart totally complete restoration and even though this paint will cost me a small fortune I would rather use good paint if I go through all the time and labor to do it.The Omni single stage paint I used on the toolbody is super tough and you really have to work hard to chip it so it should last a long time on a combine. Opinions please!
 

[Stephen Newell]

Generally you don't sand epoxy primers. On cast parts you just prime and topcoat. On sheetmetal parts where you are trying to smooth and level the primer you would apply a filler primer over the epoxy primer and sand that. Be sure you get a data sheet on any paint you use and follow the directions, especially the recoat window on the epoxy primer. Epoxy primers have to be topcoated withing a certain timeframe or have to be sanded or re-primed. Someone else more familiar with PPG primer could tell you which would be the best surfacing primer to use with the mp 170. The part of the scan compatable surfaces may give you some idea of ppg primers you could use.

 

[Rod (NH)]

MP170 is certainly capable of being applied very smoothly, providing the underlying surface is smooth to begin with. It should not require additional sanding or scuffing prior to topcoat, if within the time window on a proper surface. If you are unable to apply the 170 as smooth as you would like, look to your application process for the reason. The 170 tech sheet permits reduction of up to 10% with acetone if needed to facilitate a smooth application.

Depending on the resulting profile from your sandblasting, more than one coat may be required. Or, as Stephen recommends, a sandable surfacer may be used. Two coats of the 170 should provide a decent surface for direct topcoating over a reasonable profile. At least it has for me.

Check the wording in the latest edition of the tech sheet and make sure you are not approaching the pot life before use. You should be able to get the latest tech sheet (pdf file) here.
 

[CNKS]

No message, I misread the question.
 

[Haley]

Thanks guys, Those are the answers that I am looking for.I was planning to use the epoxy primer on all of the machine and use the filler primer to smooth up my outer sheetmetal for a smooth shine.Glad to know it will work as I had planned.