Galvanised angle trims

[guernseyman]

on the corners of my outside walls have rusted and are discolouring the paintwork. I am hoping to re-paint the walls this year but don't want the rust to be showing through shortly after. Does anyone have any suggestions as to the best solution? I know I can get an angle grinder to the plaster and remove the trims but would prefer another option as I would then have to replaster the corners. TIA.

[AlBags]

De-rust and prime them with a red oxide or other oil-based primer, before painting over the lot.

[guernseyman]

Sounds good but the plaster is covering the trims which means I have too remove that before de-rusting, doesn't it?

[AlBags]

Ah .. ok.
So the rust is beeding through?
If you want to stop it for a few years, clean the surface and seal with some Thompsons wall stain sealer down the corner areas first (2 coats) £10 a tin B&Q. It's weird smelly stuff .. white in colour.

[AlBags]

Must be render .. anyway .. right?
Cement render?

[guernseyman]

Yes, sand and cement render.
If I use this Thompsons sealer would the rust have to be totally removed or just perhaps pressure washed off?

[AlBags]

Well it must be rust stains, surely ...
So just make sure area is clean and free from grease, etc.
Rainwater and pollutants gradually erode the galvanised layer, which then allows the steel underneath to start rusting.

[guernseyman]

I'll give that sealer a go then, hopefully it will work. If not then I'll go back to the original idea of removing the render. Thanks for that, Albags