We want to embed 10" high x 1.5" deep metal letters into a concrete band. The letters come with 3" threaded studs. The concrete band will be 8" deep by 2' wide, with rebar. The letters will be flush with the finish surface of the concrete. It's a bike trail, so we want to be sure that the letters remain flush over time.

1) Do the letters need a special finish to aid in adhering to the concrete?

2) Should we apply some sort of joint material / sealer around the letter to allow for concrete settlement / movement and to keep water out of the joint?

3) What should we specify to protect the surface of the letters from the adjacent concrete while it is being poured?

4) Will a corrosion-inhibiting admixture help?

Any help would be appreciated!

Is there more information that I could provide that would help an expert answer this question?

Explain the term concrete band?

We have a few people who knows their concrete stuff here.

I think I might silicone a fine film over the face of the letters, and pour into the concrete. Not sure how bondit works with metal.
I would definitely pour concrete with letters in place as opposed to cutting into the concrete later.

The band is decorative and can be a couple to several inches wide and high.

Yes - the concrete band will be 2' wide x 8" deep, spanning the width of the trail.

It sounds like you have some metal letters with threaded studs you wish to embed in concrete. Pour the concrete, run the nuts on the studs out to the very end and push the letters flush into the wet, finished concrete.