Hi. I don't think Kiltz stops rust. It is used to prevent bleed through. I would sand the rust and steel wool it. Then apply Rustolium primmer. If you have the skill remove the steel corner bead and install plastic cornerbead.
Good Luck Woodbutcher

corner beads on what?
can you post a picture?

You can either lower the humidity (by closing the house and using AC or dehumidifiers) or replace the metal beads with plastic. Any surface treatment will be temporary at best.

Untreated metal will rust when covered with latex (water based) paint. The corner bead material apperently wasn't treaed.

They need to be sealed with a solvent based primer.

Metal Corner Beads are Galvanized so I believe lowering the humidity would be the proper thing to do. The current ones will rust through again after being sealed

Most likely those corner beads were rusting BEFORE they were installed, i.e. stored improperly. That rust will be stronger than anything you can spray/throw at it. The only permenant solution is costly and messy and that is cut them out and replace them.
Sorry...

Thanks to all for your responses. Wood Butcher, I will try the Rustoleum. :O)

Rustoleum is over rated. If you choose not to tear them out, prime them with ANY rust inhibiting primer, preferably red oxide, them prime with stain blocker, then paint with anything you want, oil or latex.

replace with plastic corner beads,
why take the chance of it happening again.

best of luck.

If your drywall was installed before 2009 I would be suspicious that it could be defective drywall that was imported from China from 2001 thru 07 - 08. That could possibly the cause of your corner bead rusting through. I know this might be out of the construction time frame but close enough to be worth the mention.
Delphi

"Piasano", could you please make a follow-up comment? How did you resolve the problem and how were the long-term results? My house is a new construction (finished early 2014). I see a lot of cracks in the stucco, rust appearing threw the stucco at most corners of the house and white stripes in those areas on the formerly beige stucco. We are still under warranty but I want to make sure this is being fixed correctly so that the problem doesn't reappear. We live in Arizona, so there is no excessive humidity here but I suspect rainwater could enter the stucco through the cracks. As with previous problems with the house, I am sure the builder and contractor will want to propose a quick fix.
Thanks!

millworkman

Metal Corner Beads are Galvanized so I believe lowering the humidity would be the proper thing to do. The current ones will rust through again after being sealed

I've seen non-galv sold at big box stores. I agree with energy: use HIGH quality plastic or vinyl.

ichabod crane, thanks for your comment. Since they are installed on the outside of the house, lowering the humidity is not really an option.

So I should probably have all corner beads removed and replaced by vinyl for a long term fix?

These are on the exterior of the home? What is your siding? Any pictures?

Yes, on the outside of the house. We have stucco. The picture shows the edge of a windowsill. As I said our house is only 1 3/4 years old.

We don't use stucco up here in snow-world, but my first thought, seeing that picture, is...water intrusion from behind?

Metal corner bead for stucco? Just sounds like a bad idea to me. They definitely sell them though, doesn't mean they are a good idea. I guess it depends on what type of stucco, if they used the acrylic based stucco it shouldn't let water affect the corner bead but if it is concrete based then those are supposed to get wet and dry normally. If the corner bead keeps getting wet it will keep rusting. I am guessing they didn't use wire mesh backing or that would all be rusty too.

Here are some vinyl ones. Best of luck.

http://www.amico-lath.com/stucco/cornerbead.htm

And here is some knowledge about stucco types.

http://thestuccoguy.com/acrylic-stucco-vs-traditional-stucco/

This has nothing to do with humidity and everything to do with proper EIFS detailing. An experienced independent consultant is the way to go here.

An over-exuberant kid with the drywall sanding pole can quickly burn through the electroplated galvanizing on corner bead, and the latex paint does the rest.

Casey

@ Caterina's post. The beads are metal ,probably sat exposed during construction , the stucco isn't covering them all over , and the paint isn't going to do all the heavy lifting on it's own.Maybe some attention to the beads before painting would've prevented this. It gets so bad here in Florida that the beads actually lift out and water gets in them. Here's an example before it's started to wear and rust...

I have used a textured elastomeric patching compound to float over all of these areas and match the finish with success. Some knife grade patches work very well. I'd clean and prime the rusted areas with a alkyd or shellac primer then cover everything with elastomeric patch textured to match then prime and paint....Should last...It's rubber.... even the paint is rubber based usually...I don't have a finished picture but, you should get the idea...

Thanks for all the comments and answers. We are currently waiting for the recommendation from the corner bead manufacturer as to which product to use to prime. Since nobody I talked to has seen this problem before, I am wondering if a unlucky combination of materials could have caused a chemical reaction which would also explain the white marks we have on the paint now in the affected areas. If anybody readings this has had a similar situation and knows of the cause and best remedy, please let me know. @beyond specialty, I will forward your info. Thanks!

Oh and by the way I have learned in the meantime that vinyl cornerbead in Arizona is a bad idea since it crumbles and dissolves over time .

That sounds like a plan. I wonder if the stucco was still "hot" when it was painted.If the stucco isn't cured for long enough, it needs to be conditioned properly as to prevent any efflorescense, which can cause paint to fail rather quickly and turn white in areas that have water intrusion. Usually where there are streaks, the paint is failing and there are settling cracks to be found. Some builder's contractors will rush and just try to load up paint on stucco that is too fresh without conditioning it first.This really isn't just limited to corner beads however and you'd know it if you saw it . Good luck!

I looked this up; they make two grades of stucco corner bead, galvanized steel and "zinc alloy" which sounds like what you would want to use outside in a marine environment. Maybe they have stainless; they make stainless expanded metal lath for stucco.

Casey

You've got to get EIFS details right.

Yikes. I wonder now how many stucco homes I've seen were EIFS systems..

google "Chinese drywall" and see if this describes your problem.