Posted by Sherman in Idaho [72.47.153.105] on Saturday, December 14, 2013 at 11:50:47 :
In Reply to: Surface Prep Before Primer posted by Rick [67.188.186.65] on Saturday, December 14, 2013 at 11:12:40 :
I'm a big fan of electrolytic rust removal. Rather than leaving a totally bare "white" metal surface, it leaves something more like a blued surface that isn't prone to flash rusting. The chemical used is just very dilute washing soda, so easy to wash off, and a bit of residue won't cause more rusting. I would have used it on the castings in lieu of bead blasting myself, since it also won't damage machined surfaces, and it will take off paint and grease if you scrape most of it off first and let it run a long time. But since you've already got them bead blasted, you still might try the electrolytic method to provide a surface treatment that's more stable.
That said, I always just paint castings with rustoleum red oxide primer followed by a top coat, and have not had problems with it coming off. It's the smooth, rust-free, surfaces that rustoleum tends not to stick to.