I read on the page of "W.S. Deans Racing Silver Solder 1 oz." on Towerhobbies' site that "Silver or Gold plating requires a special solder. Ordinary solder causes a chemical reaction which will degrade the joint. Deans Racing Solder is 2% silver with high activity ProFlux. [...] The Best Solder for Silver and Gold Plated Surfaces."
Marketing or truth?