Bricks, Masonry, Asphalt and Concrete - Prevent Corner Bead Rust Thru Stucco

I have a stucco covered chimney (presumably on a wood frame .... about 4'x3'x7' high)... 20 yrs old. I noticed that a vertical edge showed rust spots THROUGH the stucco. This was not an external stain. ('Have similar situation on a few wall edges around the house). Chipped away stucco (only about 1/4" of it) to find 1/8" metal wire that I am calling a "corner bead" (please correct my terminology). Wire brushed the metal with drill attachment, painted with Rustoleum & waited a day. Applied DAP Stucco patch, working in & around wire /stucco and let dry a day. Next day applied more patch to fully cover bead & build up stucco (to say 1/8" thick). It matched existing stucco and looked great. Had a beer and admired my work. Next day inspected and found rust THROUG the stucco. Can you advise?

Welcome to the forums

Sounds like you should have applied more rustoleum. Since there wasn't enough paint/primer to adequetly seal the rust the moisture from the stucco reactivated it. You should be able to prime the stucco with a solvent based primer to stop the rust from bleeding thru, ofcourse that is only a viable option if the stucco is painted.

Or use Phospho.