Don't Paint that Pressure Treated Wood Until It's Ready
If you are like most Americans you want to get the job done as quickly as possible. But, if you recently had a new deck built or trim installed using Pressure Treated Wood you need to curtail your urge to get the job done.
First thing that you should know is that a lot of pressure treated wood is Southern Yellow Pine, which is not the best at holding paint, and pressure treated wood really is not meant to be painted.
Next, if you do decide to paint or stain, you have to wait until the wood is dry. Pressure treated wood is wet 99% of the time when it is installed. And, the best way that I have read to explain the issue with painting or staining wet wood used a sponge analogy. So here we go. Think of the wood as a sponge. When you paint the first layer of paint, which is hopefully a primer, this paint is absorbed by the wood. This is much more true when using a penetrating stain. If the wood is wet it cannot absorb the paint. Instead it dries on top of the wood with very little, if any adhesion. Thus, in a very short time frame you will have paint failure.
Your best bet is to wait six months. Or, if you own a moisture meter, the moisture level should be 14% or less.
If you do decide to use a paint or a solid stain, than it is best to use a long drying oil primer. Oil primers penetrate into the wood more than acrylic paints, and the longer that the primer has to dry the more it will penetrate. Also, oil primers will block tannins from bleeding through better than acrylic primers.