Renee, that's exactly where my 91S13 has rust, and is NOT a good place to use swimming pool acid (unless you were to remove all the metal hardware first). As I said in the quote above, and Ron warned again (and it's worth re-repeating), don't get swimming pool acid on the metal parts like the rusting clip or it will eat even more of the coating off and cause more rust (and the stuf is dangerous to eyes and skin).
This is a good place to try Naval Jelly.
There is also a product out there called Extend, comes in liquid or spray, and seems to have phosphoric acid in it , which stops the metallic oxidation process (doesn't clean up rust in fiberglass I don't think, and might turn it black and look worse) and then forms a primer-like coating over the metal for painting
(must dry at least 24 hours with no dew). The commercial fishing supply places in Tampa sold
the liquiud in gallon jugs to the boats for swabbing down decks, masts, and other gear to retard rust.
Also, when using "rust proof" paints, like Rustoleum, read the labels, as the primers are indeed rust-retardent (but water-permeable without a top coat), but the top coats are nothing special beyond the brand name.
Not sure about this, but I believe the usual water system "rust" is usually caused by an iron bacteria and the rust is some sort of byproduct of theirs (corroding galvanized steel pipe is real rust), so treatments may actually differ.
Pete and rustless RatLadies