We have a job to install 10" high letters on a Corten steel wall panel. Originally we were going to use stud mounted aluminum letters but the contractor is suggesting we apply a sealant and glue the letters using APS 500 sealant instead of stud mount. This will eliminate the aluminum/steel dissimilar metals issue. Alternatively we are thinking of switching to PVC letters painted a metallic silver as they are lighter weight than metal letters. Is there any issue with the Corten oxidation interfering with the adhesive bond to the wall over time? Thanks!