Others have reported here that Evapo Rust can remove galvanizing. See:

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/1506951/re-evapo-rust-who-uses-it.html

Safest Rust Remover is less aggressive than Evapo Rust but might remove galvanizing or plating also. See same link.

You can try vinegar. A 1-2 hour dip in inexpensive vinegar should show significant results without hurting any zinc plating. After an hour, try physically removing rust with a brass wire brush and dish soap. If any rust remains, dip for another hour.

I've used vinegar a lot and never damaged anything.