If you read all of the posts,, that have been made so far, or will be made in the future,,
they result in three possible approaches to the removal.
1) Acid
2) Caustic
3) Mechanical abrasion
That is all there is available to you.
Lets start out with Coke, I Googled it,,
"Cherry Coke was found to be the next most acidic (pH of 2.522), and Coke was the third most acidic soda tested (pH of 2.525). Battery acid has a pH of 1.0. Pure water at room temperature has a pH of 7.0. "
So, Coke is an acid,, but, is less dangerous than muriatic acid.
Less dangerous means it will take longer to work, and will take more applications.
Lime juice, lemon juice , CLR Remover,, they are all some form of acid.
Caustics typically act as a "soap" lifting unwanted deposits off of a surface.
I have painted a lot of steel farm equipment over the years,,
My approach has always been to use caustic cleaner to remove grease, and acid and/or mechanical abrasion to remove rust.
I get great paint results,, that last a long time.
So, you can use weak acid, applied frequently over a long time,
or
a strong acid applied once (for a short period of time)
OR
use mechanical abrasion.
A 600 grit wet or dry sand paper will do it,, as well as many other abrasives.
As a side note, I just found that a similar coating is on the outside of some of the windows of my home.
It has been too cold to do much, but, I have experimented with several automotive polishing compounds,,
They all have made the glass look better.
I thought the glass was acid etched from acid rain, or something,,
but, the glass looks great after some effort.
Let us know what you end up trying,,,
