How do I paint-prep and finish a metal filing cabinet for outdoor use?

Teri: maybe this will help

https://www.familyhandyman.com/painting/15-tips-for-painting-outdoor-furniture/

You may want to lightly sand it just to give it some 'tooth' for the paint to stick. If you use a paint for metal/outdoors you shouldn't need to seal it with poly, Teri.

Spray paint it. Don't sand unless it's rusted. Use a spray primer for metal first and then paint. you don't need a top coat unless you think it will take a beating.

I think no matter what you do this will get very rusty and eventually holes through it. Especially if you fill it with soil. You may want to use pots Inside the cabinet for that part

Here's what one Hometalker did with hers

https://www.hometalk.com/diy/outdoor/garden/fancy-red-planter-made-from-free-two-drawer-metal-filing-cabinet-9374459

Hi Teri, I agree with Frugal Family Times...the type of metal that your filing cabinet is made out of is crucial to whether it will rust. I doubt you have a stainless steel metal filing cabinet. It would be fine if it was being used in a sunroom but anywhere it is exposed to the elements, you will be unhappy with how rusty it would get. Unfortunately I wouldn't spend the time on it.

If it's aluminum it won't rust. If not and you don't mind the rusty look eventually, I would say get a good metal spray paint and primer in one product and give it a few coats. Spray it inside and out covering all sides and all surfaces. It's the exposed metal that will rust, not the painted surfaces. You won't need a sealer. If you can keep it on a covered porch or under an overhang even better. Hope that helps!

wipe down with TSP(get at local hardware store ) use wire brush to remove any loose debris(rust,paint,dirt etc,) wipe down removing any loose debris let dry well paint with correct paint for whatever metal it is. most metal paints have sealer in them spray paint to cover cabinet will be expensive but you can buy rustoleum in can and apply with roller you can also use flex seal spray or tape to seal any parts of cabinet you do not water to seep out/drain from or install plastic tubs inside drawers or cabinet itself to hold soil,moisture plants

If there's no rust, you can fine sand or scuff with fine steel wool just enough to scuff the finish for paint to adhere. Clean with denatured alcohol. Then spray with a primer and then an exterior paint.