[almega]

I have some cast iron parts that I have sand blasted and there appears to be some rust still down in the pores that I cannot get out. If I let them set for a day or two, the rust kind of grows a little and the spots get bigger. There is no scale, just dark surface rust, but down in the texture of the casting. Can I treat the surface with phosphoric acid to neutralize the rust, then prime with epoxy primer and finally paint the color I want? Will this work to give me a durable finish?

[kenseth17]

I would imagine so. When I worked as an industrial painter, thats the way bare metal parts were prepped. We would dip them in an acid tank, then water, and then epoxy primed and painted, so I imagine that is the way you would do it. But don't let them sit real long before priming.

[baddbob]

Try some naval jelly, let it set for awhile then scrub with a scotchbrite pad and repeat, it may take awhile but they should dislodge. Rinse with water when done and dry, then scuff and prime. Although it is recomended, I don't like priming over the phosphoric coating, I always sand or scuff it off before priming- reminds me too much of metal conditioner- at times I had some major problems with that stuff years ago.