david wrote:
sorry i should have been more specfic its the hull and deck on a 45' steel
boat i primed it with epoxy grey primer 12 months ago now i want to put the
top coat of white polyurathane paint on but first i have to remove the
chalkiness as you say caused by uv. i dont like to sand it as i may sand
through the primer and was hopeing there was something i could wash it with
thanks

I don't think you have much choice other than to sand. The chalky
material is UV degraded epoxy that must be removed completely before
paint. Otherwise, you're putting paint over a weak surface that will
likely result in a poor bond. Think about it this way, you can either
sand it now and possibly have to re-prime, or you can paint over it, end
up with a bad and/or flaking finish and have to sand/scrape all of it
off and do it all over again. Which would you prefer?

When it comes to painting, preparation is key.