Rusty railings all lumpy and bumpy - can I get them smooth again?

[Superarchie]

Grateful for any expertise here.
I'm repainting some railings. The builders merchants gave me Hammercote smooth paint and said that I didn't need to treat the rust - if I wire brushed then sanded the paint would do the rest.
On the first section I tried it seemed to just exacerbate the lumps and bumps.
Is it worth giving it a rust treatment first? Is there a way to smooth out the rusty bumps?

[PigletJohn]

Opinions differ about Hammerite.

I think it is awful. Rust grows underneath it, and it is very hard to strip off or recoat.

Are the railings of round section, or square?

How thick do you think the rust is?

[Superarchie]

The railings I'm doing are round, but there's a gate to be done too, and that's square (at least the gate is smooth, not lumpy like the railings).
The Hammerite just went really gloopy and sticky very quickly. I noticed after I'd done it that I wasn't meant to use it in direct sunlight, and of course I'd done it on a blazing hot day. I'd hoped that if I used it when it was cooler it would work better. Thoughts?
I don't think that the rust is that thick, I guess it's just formed lumps where the water has got through the paint.
V grateful for any suggestions PigletJohn

[PigletJohn]

A wire brush tends to polish rust rather than remove it. If it is not very thick, and the metal is round, I would try a coarse wet-and-dry paper (it is like black sandpaper, but is waterproof, so you dip it in a bucket of water, and use it wet, and the paint/rust particles wash off so it does not clog).

The water you use will make a thin film of rust form, but the next day you can wipe that away with a fine (600 grade) wet and dry paper used dry.

I would throw the Hammerite away. Get a metal preservative primer from a paint shop, and a very soft one-inch bristle brush. Stir it very well and add a little white spirit if it is thick. Apply two thin coats and allow to dry according to the instructions on the tin (this is in case you leave any bare spots with the first coat, the second coat will fill them). I would then use a gloss oil paint (probably black). As you are using an oil paint, any water must have fully dried out before you start. Use Kurust (from Halfords) on any visible rust remaining after you have sanded, and allow to dry per the instructions before painting.

Keep a narrow jar of white spirit handy and slosh your brush in it if the paint starts to thicken and dry. This will not work with Hammerite.

Use disposable Nitrile gloves. White sprit eats rubber.

It is possible to use a paint roller on railings, but unless you have a lot to do, the preparation and cleanup will take a lot of the time you save, and you will still need to brush the joints.

Sanding on a square or flat surface, wrap the paper round a cork sanding block.

BTW when using a wire brush, wear goggles as wire fragments may fly off.

[Superarchie]

Thank you so much PigletJohn, I'm going to give that a go as I don't want the railings to stay lumpy.
Do you think I can get away with any shortcuts on the gate which is square edged and not rusty, just paint flaky? Is it worth using the Hammercote on that do you think?

[PigletJohn]

ordinary paint is IMO better.

It may be that it is galvanised and rust resistant, so only needs light sanding to smooth the surface and remove flaking paint.

[Superarchie]

thanks again, i will get the supplies in this weekend and crack on!