I have a cedar deck which is probably about 8 years old. The posts and spindles are painted the same color as the cedar siding on the house using the same oil based paint. My problem is that within a year or so, a lot of the paint peels off of the railings and posts. It comes off in big pieces and I am not sure why. The paint on the siding has lasted for almost 5 years and shows no sign on peeling. I have had to repaint them every couple years. Do I need to remove the paint from the railings and put on a primer or do I need to put on some type of water repellent? and then re-paint?