Hmmmmm....how flaky is the remaining paint/primer??

It almost looks like it's still peeling?!

I'd consider taking it down to bare metal again using a wire brush on a drill.
* Wipe down with Lacquer thinner.
* Prime with a good full coat of 123 Latex. There are some rust inhibitors in 123.
* Also a thought...take them off and use a spray primer like Rust-oleum Professional. This would actually be my 1st choice!
* Final paint coats could be sprayed or brushed on. Use the highest practical gloss. DO NOT USE FLAT.

Faron

Find one that is meant for exterior metal use.

Use rust-proofing primer ... The better you prep it, the less often you have to do this.

My uncle used to wax his cellar doors with car wax - he claimed it made the paint last longer.

I think I scraped about 98% of every loose scrapable edge. Drills and wire brushes probably not going to happen. Maybe you are seeing the dirt/mildew layer. close up below. WIll the lacquer thinner clean that up too?

Is that dark red under finish the "bare metal"?

Great idea to spray. I'm not likely to take them off (above my pay grade!), but opening them should make them vertical enough. I can protect the overspray I think. And thats a more palatable way to apply oil-based product. fast and disposable. Can I do the same with the finish paint?

just a follow-up to this mess.

I prepped as much as possible with sanding and scraping. I spray painted with the Professional Primer -- two coats some time apart.. I forget exactly. Then we got rain or snow or winter. I never got a chance to put the finish coat of paint on -- or even to look at it again that fall.

In the spring, much to my dismay, much of the primer was peeling. I scraped and sanded again. Re-primed. and Painted with a Ben Moore latex high-gloss Metal and Wood Enamel. I think it was a new product. I had it tinted to match the house color (taupe).

When I looked a week later, tons of peeling. It was a total mess. OMG. Very Aggravated.

A few days ago I started again and sanded and scraped again. Used my power sander this time too. Hosed off all dust and let dry well (perhaps I didn't get rid of all the sanding dust last fall. I don't recall using a hose. probably a brush or damp rag). Spray primed again. It was not supposed to rain until the next day, but it rained within 10 hours. And its been raining ever since - about 4 days. But I just looked at it today and the primer seems to be holding up. No peeling. Woo hoo!!!

I'm going to just keep the primer color on it. It needs another coat or two to smooth out the color. I will wait for another dry stretch of weather and hopefully I will be able to cross this $&*@&! project off my list.

And if it peels again, I'll just keep some extra spray primer on hand and touch up. Or get new bulkhead doors!!