Getting ready to paint my pump but have question on the rust on the pump. I had it sandblaster and have used bondo on most of the area with rust but the area around the glass curves on door edges still has some rust spots. Will the epoxy primer stop the rust from developing more? What suggestion do members have. I am going to use a single stage auto paint.

Epoxy Primer is great for preventing new rust on freshly blasted panels, but offers little to nothing over existing rust. You need to get rid of rust before priming and painting or you will be sure to see it again in the future. If you are dealing with a flash rust from the panels sitting after blasting then a metal prep wash will work. If it is anything more than that, I would either spot blast,or take a scotchbrite wheel to it or use a rust converter. But check the lables some liquid rust converters say not to use on blasted metal. Bottom line is you need to get it out of there, especially after all the work you have in the project to this point, you want it done right. You will be glad you did. Good luck.

The rust really needs to be removed totally.If being the pumps done been blasted I would recommend a rust converter which is design to stop the rust .Then apply primer etc.Epoxy will not stop rust it's design to chemical bond to bare metal (etch) so that primers and surfacers will adhere .Any local auto body supply should have the rust converter?

Ive never really found a rust convertor that worked well at all. Sometimes on casting its hard to get into the creaveces and Ive used metal prep solution and a scotchbrite pad to remove rust I couldnt get with the blaster easily. That stuff really stings on your hands! Epoxy is really helpful in preventing more rust. Also, found that POR15 and Chassis Saver are good products.

The question is how much rust? Ideally you want it gone, but after sandblasting I have found areas where the metal is pitted and the rust is gone in all but the deepest pits.

No one wants to do something twice, but you also have to be realistic about the situation. I have used Dupont 5717s etching wash and Dupont VariPrime with success for minor pitted spots.

Same situation with the pitted metal, I am experimenting on a project with epoxy primer. We will see what happens...

Again be realistic about the situation, treat it the best you can, then seal it up. Most of our pumps and such reside indoors these days. If its sealed and there is no moisture there will not be a rust problem. Rust needs oxygen and moisture to blossom!