Rusted corners in kitchen window (interior)

[SuseB]

Hello, new member here!

I'm in the process of tidying up my kitchen window surround after some water damage. I think I've solved that issue from upstairs bathroom and it seems to have been dry for about 2-3 weeks now. I've just sanded back and removed the peeling paint but some parts have crumbled away to reveal rusting corner beading (is that the right term?) on the left side and bottom of the window ledge - see photos attached.

I was hoping just to maybe use some plaster to fill in the missing corners and then paint over it, but worried that the rust will just show through again?

Any advice is welcome! Thanks

 

[opps]

The angle bead is normally galvanised but if the walls are damp, they will often rust.

Ordinarily, one shouldn't sand galvanised metal because of the risk of damaging the finish. In your case the metal has already rusted.

I'd recommend sanding the rust off and then either using a dedicated rust paint or at a minimum oil based undercoat. You can then fill the damaged areas of plaster (where it meets the angle bead) and lightly sand it (trying to ensure that you don't sand through the oil based undercoat). Then just emulsion the area as normal.

 

[SuseB]

Thanks for your advice. So do you think I should try to scrape away as much more of the crumbly plaster as possible until I find the remainder of the rust? Then I guess wire wool to sand it back.

At what point would you say it should be replaced?

 

[lostinthelight]

I would strip back the loose plaster and if the rust has got into the expanded metal,if its that type of bead, then replace them.
We had the same problem in our last house and used rust killer and oil based paint which held it at bay for about 2 years