GHS says: 
 
GHS White Bronze strings are designed to pull the full dynamic range out of your acoustic guitar, inspiring you to play longer. A highly magnetic nickel-iron alloy (Alloy 52™) is wound over a hex core, giving you a smooth feel with extra clarity and shimmer. White Bronze acoustic guitar strings are ideal for acoustic/electric guitars with magnetic pickups! Use them on the stage or the studio and listen to them come alive.
Why Should You Play White Bronze?
You're using a magnetic pickup with your acoustic guitar
You want to coax the full dynamic range out of your acoustic guitar
You want a string that can last a long time, that isn't coated