Prep will be sandpaper down to bare metal in some areas with 60 grit and just sanding with 400 grit in areas that currently look better. Then primer in question then Rustoleum gray topcoat. All with rattle cans.

This doesn’t have to look professional, but I’ll wipe down with acetone and cloth before and after initial sanding.

Rustoleum makes about five different metal primers
I’ll use their self etching on bare metal

But then there’s
Bare metal primer
Sandable and fillable 2 in 1 primer
Automotive primer
And Filler Primer

If the grays are all the same color, which primer would you put on top of the self etching?
Doesn’t matter all about the same?

Sort of leaning toward the filler primer or the 2 in 1 if those smooth uneven areas well.

I would use regular automotive primer.

I work at a railing company now as the painter in the Iron shop. Grey primer will work just fine. Clean good with acetone or thinner. I use acetone because the steel we get has an abundance of grease on it. Thinner will work, just takes longer.
All primer is sandable, and fillable. Thats just a marketing scheme
A filler primer seems excessive in this situation. Unless you're planning on putting primer on, and letting it set for a day or two. There's no need to sand it. Spray the primer on, wait an hour( i wait until its dry to the touch, but I'm doing several in a day), spray the paint on.

So glad this is up today , maybe you can help Ricks also .Yesterday we spray painted my hood with black primer after having it sanded at a body shop to a real smooth surface ,Then we wet sanded it . Another coat of black primer and it still had dark spots that would come thru . We ended up getting 2 more cans of primer and paint but it still has the dark spots . I would like to paint the top side white today . Do I spray it with white primer and let it dry and do it again ? And then a coat or two of white paint .

Here is the dark spots after it dried

When I was refinishing bathtubs, we almost always used a white primer. Just made everything easier. The pic was a little tricky to make out. When I zoomed in it got real blurry. But one thing I have learned over the last three years spraying a lot of black. You have to really stir or shake it up. When you think you have done that enough, do it again. I get occasional splotches i have to go back and touch up. I hate black paint. Never used a black primer, but would suspect it's almost equally a PITA.

Are the dark spots where they put some filler/Bondo?

My instinct would be to do a light coat of white primer, then white top coat/ light sanding with 400 grit between the two topcoats.

Thanks for y’all’s help, think I’ll use self etching then the gray primer that’s a closest color match to the topcoat.
I didn’t think there was much difference between the other five primers. My guess is the 2 in 1 is a little thicker.

Doc, is it bare metal or a repaint? If its bare metal. Self etching wouldn't hurt at all. It just stinks to high Heaven. Definitely use a respirator, and ventilate the area. We use the Duplicolor green self etching for all our aluminum.

I’ll be sanding down to bare metal in some areas (a few areas of rust and oxidation that look like they could do with a fresh start over). Most of it just needs a new topcoat really. Some areas are actually just fine the way they are.

Respirator definitely.

You would probably be alright with just a regular grey primer. We only use it on aluminum around here.

Thanks Rick.

Grind up a bunch of glass to mix in with the paint so people will keep their hands off the hand rail. It will keep the finish looking good for longer since it would probably wear longer.

Intersecting idea; but there are innocent children that use this handrail.

There are no innocents. There are, however, different degrees of responsibility. They are the spawn of the guilty.