Make sure you use many coats. I used two coats on inside of a stand made of MDF, which began to crumble where the water splashed on it near the inlet of the sump. It never failed, but, after a few years would have become a problem.
If I was doing that again, I would probably go with an epoxy paint, or else, six or eight coats of poly. Needles to say, you won't be able to re coat it with your equipment in there.
Good luck.
Ryan.