Painting - Painting concrete patio

I painted my patio a couple of years ago and need to do so again. I powerwashed it and about 1/4 of the paint came up. Should I prime it first before painting? If so, what kind of primer should I use? I did get some bubbles in the paint by the end of the first season last time, is this from hydrostatic pressure? Should I drylock it before painting?
Thanks for your help.

Welcome to the forums!

It's difficult to get a lasting paint job on exterior concrete slabs. The weather exposure and lack of vapor barrier under the slab both contribute to the paints failure. I usually recomend stain over paint for patio slabs.

Drylok might help - they make a version formulated for floors although I've never used it and don't know if it's suitable for exterior use. What brand and type of paint did you use?

I agree with marksr about using stain instead of paint on concrete because it digs in deeper.
Try using a commercial washer with a power tip. That is a 0 tip that swirls...very powerful. A lot of the paint should come up and then try a small sample area with a decent solid hide concrete stain. It will last much longer.

I think a good concrete sealer and then paint on top, is likely the easiest at this point. Every few years you'll have to repeat the process, but by then there'll likely be some wear as well. Stains are good if you are starting with bare concrete but don't wear well. Such as staining a garage floor when you have runners for the tire treads to run on.

I think a good concrete sealer and then paint on top, is likely the easiest at this point.
No disrespect Billy but...concrete sealer is very hard stuff. What kind of paint would you put on top of that?

In a perfect world, we'd recommend stripping all the paint off and just applying sealer, two or three coats, thus rendering the concrete slab able to be cleaned. But that's a lot of work and people like a painted look. Once a slab is painted with any other than treatment than sealer and epoxy, if becomes an annual or every couple year, maintenance task. So we remove the loose and scaling paint, hope to lock the situation in with some sealer, and apply another coat of paint. Next year or two, we'll chase the areas which loosen up, that didn't have sealer under them, scrape them down, and recommend the same thing. The areas that we fixed this year, will likely be tight. The more sun and rain can be kept off the area, the longer it will last.