Metal and plaster

[Carl Phillips]

Hi.

Decorating the kitchen in our old house (1850).
Around the window area there seems to be metal starting to rust and show through the plaster, I have taken the plaster away (not too much) to see what is causing the issue. It looks to be a lintel running up the entire corner of the window.
How do I prevent this from rusting and coming through the plaster either by bubbling or staining.

Thanks,
Carl.

 

[Burnerman]

It looks like plasterers angle bead thats rusting......thankfully they are stainless now.
They’ll extend around 30mm on the corner.
John

 

[bobasd]

Galvanised beading rusts and blows plaster.
The return wall shows damp. Perhaps the window reveal is ddamp under the new paint?
You will have to find the causes of the damp - a pic of the outside would help, & a pic showing the right hand side otside corner bead?
Plastic or SS angle beads are used nowadays.