AJH wrote:
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.

https://www.hunker.com/13415944/how-...th-naval-jelly

An experiment I did with this years ago, when you rinse
off the rust, any shiny metal underneath *rusts almost instantly*
after the rinse. It takes a very short time for the surface
rust to come back. This has to do with the naval jelly etching pores
into the metal and increasing the surface area. You cannot
possibly apply a finish fast enough, to stop that from happening.
You would need a finish that can be applied right over un-rinsed
pure naval jelly (which is not going to happen).

Test the process on a separate rusty metal sample you keep
for the purpose, to see what the effect will be in advance.

Don't panic if that happens. Just make sure that the finish
you're applying, after you rinse off the naval jelly thoroughly
and allow time for the surface to dry, that finish should be rated
for "application over rust".

My conclusion was, I wouldn't be using any more of this for
home projects. It's fun to play with, but doesn't change the
nature of the problem you're trying to solve.

When I refinished the steel rear landing on the back of
the house, I just used a wheel and a rust paint over top.
And this did not do well, anywhere that there was standing
water from rainfall. Since I took the wheel to the under-side
of the landing too, the finish under there held up well.
And probably won't need to be re-done. Using the wire wheel
under there, was "pure hell". I looked like a coal miner
when I was done.

Paul