This article is about painting bird baths, but it also has some tips about sealing: https://www.hunker.com/12003101/what-kind-of-paint-do-you-use-on-concrete-bird-baths
Oops, you needed to use oil based concrete paint over 2 coats of primer. Then coat with oil based polyurethane. At this point try using the oil poly and hope it holds the acrylic from peeling.
Go to Lowes or Home Depot , they have several tips of sealers ,,,,, Just what you need.
Marine varnish should work.
Get Spar marine varnish.
Thank you !
Yes marine sealer. Make sure your item
is dry first.