I have some large galvanized metal disks that I going to grind into an outdoor decoration.
Grinding will destroy the zinc covering. It'll be painted afterwards.
How can I weatherproof the metal?
i've been decorating some metal mailboxes which have been outdoors for 1.5 years and are still looking good.
If you are grinding galvanized metal, for "final finishing" I quickly found 5-10 methods on YouTube and Instructables that give some relatively easy solutions. "How to galvanize metal" was my search string.
I've been investigating electroplating steel. aka de-rustification.
Galvanizing is an interesting anti-rust technique. Most galvanizing is hot dipped, in a vat of molten zinc.
But using a zinc anode, zinc oxide electrolyte, and a steel item = electroplating (OUTSIDE - allow H2 gas to escape & not explode) is quite easy. No super nasty chemicals needed either. Happy re-surfing (researching) and investigating
Depending on the type of paint, it should form an able enough barrier. Fun fact, to prevent the rusting of large, steel, salty sea-faring boats, they connect large blocks of zinc to teh hull on the inside. The zinc "protects" the outer steel layer by basically transferring the corrosion to it (there's a lot more chemistry involved but that's basically what happens).