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!
Whenever I venture into uncharted waters like this, I always rely on a tested method. Stud mounting seems to be fail safe.
If anyone here has clear-coated Corten successfully and then installed heavy letters on it using adhesive, and had it last long-term, it would be good to know. I know I haven't. That means any recommendation for adhesive mount would be pure guesswork, right? And recommending a clear coat would be a guess, too.
I wouldn't know what clear coat would be appropriate. Matthews has no protocol for clear coating Corten.
Corten's website even declines to give a recommendation.
They say to ask "your paint supplier because they are the experts." That does not inspire confidence.
They also say that if you clearcoat, "do it after it has a good patina set into the steel." Otherwise, they say, "it is very likely your clear coat will take off the rust." Huh? That doesn't inspire confidence, either.
Stud mounting seems the safe way to install these letters.
It's true that certain dissimilar metals have a galvanic reaction when in close contact with each other in the presence of moisture. The Corten site says to not let galvanized steel or zinc-coated steel be in contact with Corten. I would probably not let aluminum letters be in close contact, either. Of course, I don't know for sure that there would be a problem. I'm guessing on the side of caution. Therefore, I would probably not flush mount them. Nylon or rubber standoffs, even if only a quarter-inch deep, might be a good insulator, and it's easy to do.
Will the aluminum studs react with the Corten? I don't know, but if you apply silicone to the stud by poking it all the way into the caulking tube, it will be completely coated in silicone. Would not that fix it?
Stainless studs would not react to Corten. They might react with aluminum letters, though. Would it be a problem? I don't know, but you could dip the end of a stainless stud in silicone before you screw it into an aluminum letter. I have never put stainless studs into aluminum letters before, so I don't know if it's a problem.
Without testing and knowing for sure, I would not attempt to clearcoat Corten and then glue letters to it, as the contractor suggested.
However...I would not hesitate to suggest to the contractor that HE clear coat the Corten. Then I would give HIM the letters to install with his favorite adhesive. I would even make a mounting pattern for him at no charge. And I would say, "Let me know how it works out, okay?"
Brad in Kansas City
https://www.corten.com/frequently-asked-questions.html
