One of those jobs I've looked at and passed by for years is our front
gate. It's not been touched in 41 years and probably not before that for
a while.

The posts are steel square RHS and the gates welded mild steel with
scroll patterns. They appear to have been primed with a zinc rich paint
like galvafroid and then painted black. Now about 50% of the surface is
rusty.

I can wire brusk the rust and paint over with smooth hammerite but
wondered if it was worth applying some phosphoric acid based rust eater
and deterent first. If so what is a cheap source as those little tubs
for rust spots on cars are far too expensive.