Rusty surfaces need a good sand, remove as much rust as possible, scrape off all flaking paint then wash away all dust from the sanding. I recommend washing it twice. Remove the handles, I took a photo from the back of the handle, to be sure they were reinstalled correctly.
The painting was a three-step process I used Killrust paints from Wattyl.
Step 1. Killrust Rust-Eater this converts rust, to stop any further corrosion. The directions don’t specify this but it is important only spot-paint rust-eater on the rusted areas. If you paint rust-eater over the entire project it could mean the top paint will not dry or at best remain tacky – I found this out the hard way, I gave Wattyl the feedback, and because the directions on the product are unclear they gave me replacement paints.
Step 2. Killrust Metal Etch-Primer again fights rust and provides a second barrier to rust, it is good for smooth surfaces as it provides great adhesion. I used a grey primer.
Step 3. Killrust Topcoat Gloss Enamel another rust inhibitor layer. I choose Bright Green, two coats. The topcoat also comes in spray paint, but I wouldn’t use a spray paint for a job this size.
I used a mini, low pile, mohair roller and a paint brush for edges, corners and drips etc. I just scrubbed the handles as they were also spotted with rust.
The paints are very smelly, so store your painted project out of the house for as long as you possibly can. Mine are still in the garage, as a result these photos aren’t great, I’ll post more photos when the lockers move indoors.