I painted some farm machinery for display in an open air museum, i used smooth hammerite and apart from a bit of fading and the odd chip its still spot on 35 years later.
In the early 90's I painted a set of railings with complete confidence in smooth black hammerite, the finish failed within a year, the only difference was that I used a rust killer, perhaps jenolite, before painting. I stripped the stairs back and reapplied with just Hammerite and it was and still is a good protective coating.
The worst thing about Hammerite IME is that its a crap paint to get a brush finish on and once applied you can only recoat with confidence using Hammerite and even then you still get a certain amount of flaking in the hard to key areas.
I don't use it any more because I want to get better finishes, i almost exclusively use Craftsmaster paints for metals and International for Fiberglass, both capable of being brushed on and leaving fantastic gloss finishes
I do use Lechler two part epoxy primer on most things though, rock hard waterproof and and sticks well!
