Drywall: Rusted corner bead

The metal corner bead on many outside edges has started to rust and bleed through the paint in my house (10 years old). This has happened in high humidity areas like the bathroom as well as regular humidity areas like the dining room. It has happened in areas that were painted in the last year and areas that still have the original 10 year old paint. The only thing I can think is defective corner bead - perhaps not galvanized properly or something?
I pulled some corner bead off and there are large patches of surface rust on them. I've decided that rather than mess with Kilz or Rustoleum, I'm going to replace the corner bead with vinyl. If I tried to treat the metal I'm thinking I would probably have to sand down to the metal to get rust off which seems as much or more work as just ripping it out and replacing. I'm thinking I will use adhesive on the new vinyl rather than any nails or screws. Reasonable?
I'm going to start with one room first as a test. All the corner bead is off (as well as baseboards, etc). I have some questions about installing the new corner bead. Before installing do I need to remove (by sanding) the existing paint / compound for a few inches? I'm not sure that if I install the new corner bead whether it will blend with the existing area unless I 'take some off' to give me room to feather. Or do I just feather over the painted surface and build it up? Will all these raised edges be really noticeable?
Suggestions / insights please. Thank you.
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your remedy seems reasonable if you're up to it, but I don't think the corner beads should be rusting unless there's a moisture problem. As for installation, I'd knock down any rough edges but I wouldn't bother with removing paint/compound for feathering. Sooner or later you'll have to float the mud over existing wall.
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There were times in the winters of past years when the humidifier was set to 'max' which is a 40-45% humidity setting. However, I'm not sure that 'max' setting really translated to 40-45% humidity in the house. I think it resulted in 30% or so. Perhaps it is related to that?
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