Body Filler question

Daniel H.

Member
I need to repair a small dent in the nose of my Farmall Cub's hood before I paint. I have it stripped to bare steel. Should I apply the Bondo before or after the primer? I am using PPG DPLF epoxy primer. Thanks.
 
Either, as long as you are using an epoxy. I personally prefer epoxy first, then filler but many prefer filler first instead. If you were using any primer other than epoxy, I'd definitely put the filler first. See PPG's filler instructions <a href="https://buyat.ppg.com/refinishProductCatalog/ServeFile.ashx?FileID=e1688339-1bb1-4a90-902f-62717793cd78">here</a> regarding epoxy dry time before applying filler (2 coats epoxy = 16 hrs dry before filler). I also like to complete any filler application within the epoxy time window (7 days max for DPLF), even though the epoxy gets a scratch first. I don't know if there is any chemical bond assist in doing that but it doesn't harm anything and might help. I haven't had a problem with adhesion between the filler and epoxy, even years later.
 
PS: After the filler work is completed and leveled to my satisfaction, I always spot the filled area with another coat of epoxy before proceeding with a surfacer or topcoat. Polyester fillers absorb moisture and I like to have that overcoat of epoxy to provide additional moisture protection in that area. In addition, if you are not applying a surfacer, that spotting of epoxy provides a uniform underlying color for the topcoat.
 
I will be way over the 7 day window before I am ready to top coat, so i had planned to scuff and apply another coat of epoxy just before topcaoting. In fact, I am thinking of assembling and running the tractor before topcoating, as I have had every bolt out of this tractor and would like to find any mechanical problems before topcoating. Then I would pull the hood and wheels, scuff it, wipe it with wax and grease remover and then lay down the red. What do you think? Also, is a surfacer really necessary? I want it to look good, but not "over done". There are no rust pits on the sheet metal.

Thanks.

 
I think the top coat will adhere better using a surfacer. Hal
PS: I used it on this garden tractor.
24giqmc.jpg
 
I believe that the use of a surfacer on cast items is a waste of effort and money since that type of surface is naturally rough to a certain extent. Whether you should use one on the sheetmetal depends on how smooth the surface actually is after your bodywork and application of the epoxy. Generally, you'd want to use a surfacer on the sheetmetal. However, I have found if the surface is sandblasted and there are no imperfections other than a typical blast profile, that a surfacer is not needed provided the epoxy application (two coats) flows well and is nice and smooth. If there are any imperfection or roughness that is courser that a 360/400 grit sandscratch, then a surfacer should be used. When in doubt, always use a surfacer within the epoxy window and final sand with 360/400 grit. That way, you will have prepared the surface best for a smooth, high-gloss topcoat finish.

My preference is always to prepare and finally paint all parts individually, not just the sheetmetal, except for a bare chassis. That's the only way to properly cover the backsides of the many items that are attached to a tractor. Or even get a decent coverage of any areas of the main chassis that are partially or completely blocked by attached components. Some don't go to that trouble but that's up to you.
 
I always use a surfacer on sheet metal, except for things like battery boxes, provided they come out smooth, so the next sentence is immaterial, to me anyway. But, the very best bond, in my unproven opinion is between epoxy and topcoat, due to the adhesion of the topcoat applied wet on wet. Some use a second epoxy application over surfacer and then topcoat. Whether that is needed, I don't know, and as yet I haven't tried it.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top