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I refinished a heat riser pipe in my bathroom a year ago. I stripped off the decades of paint using a combination of elbow grease + tools: putty knife, electric grinder with wire wheel, and sandpaper. I stripped that pipe GOOD and got it down to bare metal.
I cleaned the pipe well with mineral spirits before painting. I used heat resistant brush on paint, silver colored.

A little over a year later, the paint is starting to flake and separate from the pipe…I can see rust coming through the paint film. Gah!

It was a BIG MESS to strip that heat riser and I ended up painting the bathroom afterwards. I am not looking forward to redoing this, but I must. I also have a couple other heat risers to paint in other rooms as well as three radiators (the radiators will be disconnected and painted in another location.

Can anyone offer some prep/paint tips for the heat risers so as to avoid the rusting?
Note that the heat riser WAS NOT primed prior to painting with heat paint. It was my impression that no primer was needed and that the point of the heat paint was that it is formulated as a very thin paint film so as to transmit more heat , and a primer would add to the film thickness, negating that function. Also, is it Ok to paint the risers when the heat is on, as it;s heating season now?