Ferric Chloride Etching

Hi
I've been looking through the forum and read about using ferric chloride for etching onto copper. I've been reading Tips and Shortcuts for Jewellery Making by Stephen O'Keefe and he says to use ferric chloride for etching onto old nikel silver cutlery when all the plating has worn off. I regularly use old silver plated cutlery in my jewellery but what I would like to know is whether ferric chloride would work on silver plated cutlery with the plating still on, or would i need to use ferric nitrate?

Any help greatly appreciated

:)