PPG Primer, catalyst and associated questions

Luke Rhonemus · Apr 23, 2013

We are in the middle of restoring a Farmall Regular and are using PPG Epoxy primer and reducer. Have never sprayed this before and wanted to know a few things. First, I was informed that it needs painted after 5 hours, but should be painted immediately or else it needs scotch brited completely. Can it be wet sanded in the mean time to provide a smoother surface? Also, what ratio of reducer to primer do you recommend for the best job? And lastly, what air pressure should the gun be operated at to shoot this type of primer? Any advice would be appreciated. Thanks!

Anonymous-0 · Apr 23, 2013

I'll chime in altho' others with way more experience will as well. I've worked with just what your working with and here's what I know.
1. Ratio of primer/catalyst is 2:1. I throw in a little primer just to get it to flow thru the gun. There is no ratio given for primer as reducer is not called for. You have about a 4 day window to topcoat, otherwise you must scuff with scotchbrite and reshoot primer. DO NOT prime/paint below 70 degrees and preferably low humidity. On a nice day you can topcoat within one hour of priming. (at least i did with no bad results.)
2. I set the compressor at about 75 lbs. and the gun at about 20 lbs. Worked for me.
3. the primer is non sandable. If your prep work on the tractor is first rate , you'll come out with a nice smooth finish with the primer. The metal prep work, btw, is 90% of the process.
4. I strongly urge you to get a supplied air system. Your health is more important than painting the tractor.
My .02.

RandyB(MI) · Apr 23, 2013

I am a PPG guy and don't usually go for any paint lines "economy" version but in the case of epoxy I use the PPG Omni version of their famous epoxy primer. It is about half- two thirds price and it handles exactly the same and I couldn't tell the diff. I use no reducer in epoxy. It may seem to go on a little rough but just turn down the air pressure and dump it on smooth. I think one can fudge on the re-coat window a little and even go to 7 days without scotchbrite. Sounds like ya got a good handle on it. RB

CNKS · Apr 23, 2013

If you are using HVLP there is no easier primer than epoxy to use. As stated use 2 parts primer to 1 catalyst (the catalyst does NOT contain isocyanates). Use no reducer. Use the air pressure at the gun according to the amount stamped on the gun or in the instructions. Do not experiment because HVLP guns vary from about 30 to 50 psi, depending on the manufacturer. You have 3 days to topcoat the Omni version or 7 days to do the expensive version, otherwise you scuff and reapply. It can have surfacer or topcoat applied after 30 minutes. You do need supplied air for the hardener used in urethane, if that is what you are going to use.

Luke R · Apr 26, 2013

You mentioned hardener. Should I put hardener in with the epoxy? We have the omni version. Also, I was wondering if it is sandable at all after applying? It sounds like it is set as soon as you spray for paint. Probably wouldn"t be good to use with the sheetmetal then? Thanks for the advice

CNKS · Apr 27, 2013

Epoxy has to have the catalyst or it won't work. it is ideal for sheet metal, cast or whatever. It is NOT sandable. On sheet metal it will give a good enough finish when top coated. For best results use a sandable surfacer over the epoxy. On relatively smooth surfaces such as battery boxes, generators, starters etc, or anything that is not the hood, gas tank, grill, etc, epoxy is fine when topcoated. A sandable primer, high build or otherwise does not adhere as good to the bare metal as epoxy. It is the only true primer that I use.

Luke R · Apr 27, 2013

Can you spray multiple coats? If so, what are the correct steps to ensure it looks good? Again, thanks to everyone.

PPG Primer, catalyst and associated questions

Luke Rhonemus

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Anonymous-0

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RandyB(MI)

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CNKS

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Luke R

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CNKS

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Luke R

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