Paint for structural steel

[cwr]

Hi folks

 

I have some steel work to paint for our outbuildings. It is exposed on the inside of the unheated building, though mostly covered and protected from rain. Is currently bare steel and not yet installed. Any recommendations for a suitable paint?

 

I can get Johnstones Agricultural Oxide locally,  though I think it needs a primer (Johnstones quick dry zinc phosphate possibly?)

 

I've also seen this Agrox stuff, I think it can go straight on. The picture look suitable agricultural, and this from it's description sounds appropriate:

 

"Agrox Grey Oxide Paint has been specially formulated to protect agricultural and industrial metal structures exposed to harsh environments. Ideal for use on barns, haysheds, and similar buildings"

[Onoff]

Galvafroid, MIO (micaceous iron oxide), black bitumastic etc. But then I'm old school.