i have an 02 and bought sliders, so i put 2 thin coats of clean metal primer on then 3 coats of hammerrite paint, anyway 24 hours later the paint is dry, but i can scratch it off with my fingernail... i thought this paint was supposed to be super hard.....???? any ideas

 

Did you clean them before you painted?

I painted my the same way as you and mine have held up pretty well.
You may want to use some fine grit sandpaper to lightly scuff up the metal to allow the paint grip.