Brass is usually an alloy of copper and zinc (bronze is usually copper and tin).
It is my understanding that copper is not great for plant roots. This kalanchoe thyrsiflora (paddle plant) has been growing in a copper pot that I made for about a year.
It's not the healthiest paddle plant that I have, and maybe that's because of the copper, but it is also in shitty soil and lives in a north facing window sill.
I like working with copper, and have plans to make more copper pots in the future, but my plans include figuring out how to seal the copper so that it won't leach into the soil or roots.