what is the most effective primer to use on a cast iron tub before painting it with tub enamel?

Question

ive used tub enamel from menards and applied it as directed( with proper prepping), but it peeled within a year. the area that peeled the worst was the floor of the tub where the original glaze(PINK!!!) was somewhat worn and therefore porous.i realise i have to strip the enamel i applied last year, but if it try again...i want to make sure it lasts. after some research...i beleive the problem i had was lack of a proper binding primer.
thank you for your help! :)

Answer 1

Try two-part polyester primer and paint. These types of coatings have very high bonding power. They don't dry like a typical paint, but cure through a chemical reaction. They are very tough and durable, and will hold up under extreme conditions.
If any of the remaining porcelain is shiny, you have to roughen it with the black Aluminum Oxide sandpaper. Use a coarse grade, this will give the paint plenty to hang on to. Other than that, follow the primer and the paints' prep and application instructions. The result should last a long time.