Hot answers tagged corner-bead
I was able to find up to 2 1/2" wide corner bead at Home Depot. According to my calculations (5/8" + 5/8" + ~1/2" = 1 3/4"), this should be more than wide enough to cover your corners. The nice thing about paper-faced/backed corner beads, is that you don't have to use nails or screw to install them. You install them the same way you would tape a normal ...
Examine any corner in any building and you'll find that the paint is on plaster, not metal. (Interior paint - even with primer - will scrape off of metal way too easily) The plaster is supposed to just cover the metal corner, neatly. In short - your drywallers (if these are the same guys who botched all the screws) suck.
You want to take a moderate to fine grit sandpaper and try to sand as much of the visible rust off as possible around the outside corner. Don't be concerned about plaster or drywall damage just yet. Next get a good rust sealing primer like this product: Spray liberally along the outside corner until the metal is fully covered. Next, spackle then sand ...
I'd be tempted to cut back your double sheets 1/2" to 3/4", make sure the resulting pocket was relatively square (or rectangular), and then screw a piece (or pieces) of scrap wood (ripped down to the right size) into the gap. You could drill diagonal pilot holes and get the screws to engage the stud. Then tape and cornerbead the whole deal.
I've used them before and they do make it a lot easier, especially if you have trouble keeping paper still from moving in the corners, as I do. I don't think they have any structural benefits or anything like that so if you have trouble with paper tape, try them out in a corner and see if it's easier. You can always take it out and go over it with tape if ...
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