Plate steel is very popular finish. All the commercial millwork and retail displays I've seen going out in the last few years, liquid nails. Sets faster than silicone.

Just have to solvent wash the back, well.

 

I'd go the opposite as I know silicone will withstand heat very well. An hour of cure time will be more then adequate for it to setup stiff enough to hold fast until cured.

 

They do a high heat silicone designed for use in fireplaces. I think it's even sold in lowes/HD . That stuff would def hold up.

 

I've taken standard silicone and subjected it to the flame of a propane torch. Not much happens.

 

Definately silicone. Construction adhesive is VERY HIGHLY FLAMABLE!

We do some powder coating at 400 +- deg, & all the premade plugs & such are silicone. If I remember right, std silicone is good for 400+ deg. The High temp stuff like used for flues & such is much higher. Go to the Hilti site for more info.

One might consider epoxy, but silicone is light years better in the flexability aspect. Epoxy is plenty strong, & high temp, but has a low modulus of expansion (think rubber band stretch). I'm thinking silicone is about 400%, & epoxy is about 40%.

 

How about a few screws that are powder coated to the same color

 

I'd spend the extra few bucks on the high heat silicone. I think the customer would feel the same way.

 

Regular RTV silicone is good for nearly 400 degrees, high heat is rated for almost 600, save your money and use the cheap stuff.

 

I would doubt very much that any part of that metal would get hotter then 180F

 

Thanks for all the input. Silicone it is. I'll see if I can track some down that is specially configured for heat.

 

I think even HD has it in the HVAC section. Any local fireplace/hearth shop will have it, that's where I get it. Funny, last time I bought it there the "tech" told me that he almost never uses it for the vents as it's "overkill".